INFLUENCE OF Tb3+ SUBSTITUTION ON STRUCTURAL AND ... · 2 1 influence of tb3+ substitution on structural and electromagnetic properties of nicuzn spinel ferrites minor research project

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INFLUENCE OF Tb3+ SUBSTITUTION ON STRUCTURAL AND

ELECTROMAGNETIC PROPERTIES OF NiCuZn SPINEL FERRITES

MINOR RESEARCH PROJECT

FINAL WORK DONE REPORT

(FROM 15TH MARCH 2013 TO 15TH MARCH 2015)

SUBMITTED TO

UNIVERSITY GRANTS COMMISSION

WESTERN REGIONAL OFFICE

PUNE – 411007

BY

SMT. S.M.KABBUR

DEPARTMENT OF PHYSICS,

SHRI SHIVAJI MAHAVIDYALAYA,

BARSHI - 413411

DISTRICT-SOLAPUR.(M.S.)

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SHRI SHIVAJI SHIKSHA N PRASARAK MANDAL, BARHSI ’S

Shri Shivaji Mahavidyalaya, Barshi.

( Arts & Science - Junior & Senior )

Post Box-4,A/P Barsi-413411,Dist.-Solapur,MH–India

NAAC Re-accredited “A ”Grade

I/C Prin.Dr. P. R. Thorat, M. Sc., M.Phil., Ph. D.

Off. : (02184) 222382 Fax : (02184) 222382 E-Mail : [email protected]

Jr.Reg.No.HSC/976/13792 (S.Y.)dt. 7-5-1976Sr. Affi. Letter No. GEN/Affi/2832 dt. 4-3-1964 Shivaji Uni.

P.G.Language / BG / BUTR / I / 30471 dt.27-5-1972Social Sciences / PW / BUTR / 3906 / dt. 30-9-1972

Ref. No.SSMB/Sr./UGC/ Date :

To, The Joint Secretary,

Western Regional Office,

University Grants Commission,

Ganesh khind, Pune-411007

Subject: - Final Report Submission of Minor Research Project

Ref: -Approval Letter No F-.47-462/12 dated 15-03-2013

Respected Sir,

I am forwarding herewith, two copies of the Final Completion report of

minor research project entitled “Influence of Tb3+ Substitution on Structural

and Electromagnetic properties of NiCuZn Spinel Ferrites ” duly completed by

Smt. S.M.Kabbur from Physics Department of this college, along with the

audited statement of expenditure and summary report of the project.

I request you to accept the same & kindly release the remaining

amount of Rs.25,000/- (In words Rs. Twenty five thousand only) towards

the project.

Thanking You

Yours faithfully

Encl:-as above Copy to:- Director

INFLIBNET Centre, Gandhinagar,

An Inter University Centre of University Grants Commission,

Infocity Gandhinagar - 382007. Gujarat, INDIA.

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INDEX

SR. NO. DETAILS PAGE

NO.

1 Audited Consolidated Statement of

Expenditure with item wise details under ‘non-

recurring & ‘recurring’ heads for the amount

actually incurred duly signed by the Principal

& C. A. with stamp & Registration No.

Annexure III

4

2 Statement of Expenditure on Field Work, if

applicable, in the prescribed formats as per

UGC guidelines. Annexure IV

6

3 Audited Consolidated Utilization Certificate

for the amount actually incurred, duly signed

by the Principal & C. A. with stamp.

Annexure V

7

4 Certificate (Utilization of grant within tenure) 8

5 Accession Certificate (Books and Journals)

9

6 Assets Certificate.(Equipments) 10

7 A copy of the proof about uploading of

Executive summary of the report, Research

documents, monograph, academic papers

published under Minor Research Project on

the website of the College

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8 Annual Report 12

9 Final Report 15

10 Final report of the work done in the prescribed

formats as per UGC guidelines

19-84

11 papers published 85-87

12 Acknowledgement 88

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Annexure-III


BAHADUR SHAH ZAFAR MARG

NEW DELHI-110002

Statement of Expenditure in Respect of Minor Research Project

1. Name of Principal Investigator : Smt. S.M.Kabbur

2. Deptt. of University/College : Department of Physics,

Shri Shivaji Mahavidyalaya, Barshi413411

3. UGC approval No. and Date : F-.47-462/12 dated 15-03-2013

4. Title of Research : “Influence of Tb3+ Substitution on Structural and

Electromagnetic properties of NiCuZn

Spinel Ferrites”

5. Effective date of starting the project : 15th March 2013

6. (a) Period of Expenditure : From15th March 2013 to 14th March

2015

(b) Details of Expenditure :

Sr.

No.

Item Amount

Approved in Rs.

Expenditure Incurred

in Rs.

I Books/Journals 5,000/- 5,146/-

II Equipment 100,000/- 100,761/-

III Contingency 15,000/- 15,004/-

IV Special need 10,000/- 10,088/-

V Travel/Field work 10,000/- 10,005/-

VI Chemicals and Glassware 15,000/- 30,833/-

Total 1,55,000/- 1,71,837/-

c) Staff : Not Applicable (minor Research)

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7. If as a result of check or audit objection some irregularity is noticed at later

date, action will be taken to refund, adjust or regularize the objected

amounts.

8. It is certified that the grant of Rs.1,55, 000/- (Rupees One lakh fifteen

Thousand only) sanctioned from the University Grants Commission under

the scheme of support for Minor Research Project entitled “Influence of

Tb3+ Substitution on Structural and Electromagnetic properties of

NiCuZn Spinel Ferrites” vide UGC letter No. F-.47-462/12 dated 15-03-

2013 has been fully utilized for the purpose for which it was sanctioned and

in accordance with the terms and conditions laid down by the University

Grants Commission.

Principal Investigator PRINCIPAL

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Annexure - IV



NEW DELHI – 110 002

STATEMENT OF EXPENDITURE INCURRED ON FIELD WORK

Name of the Principal Investigator: Smt. S.M.Kabbur

Certified that the above expenditure is in accordance with the UGC norms for Minor

Research Projects.

PRINCIPAL INVESTIGATOR PRINCIPAL

Name of the

Place visited

Duration of the

Visit

Mode of

Journey

Expenditure

Incurred (Rs.)

From - To

Solapur University ,Solapur 10 May 2013 Car 1200/-

Solapur University ,Solapur 10/07/2014 Bus 200/-

Solapur University ,Solapur 23/07/2014 Bus 200/-

Dr.Vasantraodada Patil

Mahavidyalaya,Tasgaon

20-25 Nov. 2014 Bus 1005/-

Savitribai Phule Pune Univ,Pune 27/11/2014 Bus 800/-



Solapur University ,Solapur 5-7 May 2015 Car 3000/-

Solapur University ,Solapur 1-2 June 2015 Car 2000/-

Total 10,005/-

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Annexure – V




Utilization certificate

It certified that the grant of Rs.1,55,000/- (Rupees One lakh fifty-

five Thousand only) sanctioned from the University Grants Commission

under the scheme of support of Minor Research Project entitled “Influence of

Tb3+ Substitution on Structural and Electromagnetic properties of

NiCuZn Spinel Ferrites” vide UGC letter No. F-.47-462/12 dated 15-03-2013

has been fully utilized for the purpose for which it was sanctioned and in

accordance with the terms and conditions laid down by the University Grants

Commission.

If as a result of check or audit objection, some irregularity is noticed at a

later stage action will be taken to refund or regularize the objected amount. Total

actual expenditure incurred for this project is of Rs 1,71,837/- (Rs. One lakh

seventy one thousand eight hundred and thirty seven only.)

Principal Investigator Principal Statutory

Auditor

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NEW DELHI-110002

(Utilization of grant within tenure)

CERTIFICATE

It is certified that the grant of Rs.1,55,000/- (Rupees One lakh fifty-five

thousand only) sanctioned from the University Grants Commission under the

scheme of support of Minor Research Project entitled “Influence of Tb3+

Substitution on Structural and Electromagnetic properties of NiCuZn

Spinel Ferrites” vide UGC letter No. F-.47-462/12 dated 15-03-2013 has been

utilized within the period 15th March 2013 to 15th March 2015 of minor

research project.

Principal

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NEW DELHI-110002

ACCESSION CERTIFICATE

(BOOKS AND JOURNALS)

Minor Research Project

It is certified that the grant of Rs.5,146/- (Rupees Five thousand one

hundred and fourty six only) sanctioned to Smt.S.M.Kabbur by University

Grants Commission vide its sanction letter No. 47-462/12 (WRO) dated

15.03.2013 has been utilized for the purpose of books and journals and the same

have been accessioned and noted in the accession register from accession Nos.

9028 to 9035, 9036 to 9042, 9104 to 9105 and 9106 being maintained by the

college. The last accession number prior to the utilization of these grants for

books purchased from UGC was 9027.

Principal Investigator Librarian Principal

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NEW DELHI-110002

ASSETS CERTIFICATE FOR EQUIPMENT

Minor Research Project

It is certified that inventories of permanent or semi permanent assets

created / acquired wholly or substantially out of the grants given by the

University Grants Commission vide UGC letter No. 47-462/12 (WRO) dated

15.03.2013 for purchase of equipments are being maintained in the prescribed

form and are being kept up to date and the equipment are registered in the

accession page No. 1 of department of Physics, Shri Shivaji Mahavidyalaya

Barshi.

Principal Investigator Head of the Department Principal

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NEW DELHI-110002

(Project Report, papers etc. uploading on college website)

CERTIFICATE

It certified that the executive summary of the report, research

documents, monograph, academic papers published under Minor Research

Project entitled “Influence of Tb3+ Substitution on Structural and Electromagnetic

properties of NiCuZn Spinel Ferrites” funded by University Grants

Commission(WRO) Pune to Smt. S.M.Kabbur are uploaded on the website

of the College www.ssmb.org.

Principal

http://www.ssmb.org/

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Annexure -VI



NEW DELHI – 110 002.

Annual Report of the work done on the Minor Research Project.

(Report to be submitted within 6 weeks after completion of each year)

1. Project report No. 1st /Final : 1st

2. UGC Reference No.F. : 47-462/12(WRO), dated 15/03/2013

3. Period of report: from 15/03/2013 to 14/03/2014

4. Title of research project : “Influence of Tb3+ Substitution on Structural

and electromagnetic properties of NiCuZn Spinel Ferrites”

5. (a) Name of the Principal Investigator: Smt. S.M.Kabbur

(b) Department. : Physics

(c) College where work has progressed : Shri Shivaji Mahavidyalaya Barshi

6. Effective date of starting of the project: 15/03/2013

7. Grant approved and expenditure incurred during the period of the report:

a. Total amount approved Rs. : 12,5000/-( First year)

b. Total expenditure Rs. : 1,30,000/-

c. Report of the work done: Separate sheet is attached

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i. Brief objective of the project :

1) To synthesize NiCuZn ferrites which are the single most ferrite

requirements for MLCI application by autocombustion method using

glycine as the chelating agent.

2) Terbium(Tb3+) has high magnetic moment of 10.6 Bohr magnetons and

hence the substitution of Tb3+ should enhance the properties of ferrites.

3) To characterize the samples by X-Ray diffraction,SEM, and EDAX etc.

4) To study the dielectric properties of the ferrites.

ii. Work done so far and results achieved and publications, if any, resulting

from the work (Give details of the papers and names of the journals in which it

has been published or accepted for publication): The work done will be

communicated to the international journal of physics before completion of

project.

iii. Has the progress been according to original plan of work and towards

achieving the objective. if not, state reasons: Yes

iv. please enclose a summary of the findings of the study. One bound copy of

the final report of work done may also be sent to the concerned Regional Office

of the UGC.: N/A

v. Any other information: N/A


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Report of the work done in First Year

1) Literature survey is done on the NiCuZn ferrites. The fabrication of spinel

structured ferrite nanoparticles has been intensively investigated in recent years

due to their unique physical and chemical properties and technological

applications in high density magnetic recording & MLCI. NiCuZn ferrites are

best suited for these applications.

The permeability in spinel ferrites can be increased by lowering the

magnetostriction constant. The magnetostriction constant of NiCuZn is low.

The substitution of Tb3+ should enhance the magnetic properties of the ferrites.

Later on the characterizations are carried out to confirm the spinel ferrite

formation.

2) The said ferrites were synthesized as follows. A series of six samples with

general formula Ni0.25Cu0.30Zn0.45TbxFe2-xO4(x= 0.00,0.025,0.05,0.075,0.1 and

0.125) was prepared by autocombustion method using glycine as the fuel.

Stoichiometric ratios of AR grade (Ni(NO3)2.6H2O), (Tb(NO3)3.5H2O),

(Cu(NO3)2.5H2O), (Zn(NO3)2.6H2O) and (Fe(NO3)2.9H2O)(99.9% pure Aldrich)

were mixed with glycine(sd fine) in distilled water to prepare the precursor

solution [10]. The solution when heated on an electric heater at 500oC formed a

gel and then ignited in a self propagating combustion to form a fluffy powder

ash. The powder was then grinded and presintered at 650oC for four hours. For

DC resistivity and dielectric measurements,cylindrical disc shaped pellets of the

samples were prepared by using a Hydraulic press machine and applying

pressure of 10 tons/m2 for five minutes to the mixture of granulated fine powder

mixed with PVA as binder. The pellets were finally sintered at 900oC for two

hours and used for XRD and FTIR characterization.

3) Prepared ferrites were characterized by using XRD spectra,SEM, EDAX

and FTIR spectra etc.

4) Prepared ferrites were tested for dielectric and magnetic properties.

Principal Investigator Principal

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Annexure -VI



NEW DELHI – 110 002.

Final Report of the work done on the Minor Research Project.

(Report to be submitted within 6 weeks after completion of each year)

1. Project report No. 1st /Final : 1st

2. UGC Reference No.F. : 47-462/12(WRO), dated 15/03/2013

3. Period of report: from 15/03/2013 to 15/03/2014

4. Title of research project : “Influence of Tb3+ Substitution on Structural

and electromagnetic properties of NiCuZn Spinel Ferrites”

5. (a) Name of the Principal Investigator: Smt.S.M.Kabbur

(b) Department. : Physics

(c) College where work has progressed : Shri Shivaji Mahavidyalaya

Barshi

6. Effective date of starting of the project: 15/03/2013

7. Grant approved and expenditure incurred during the period of the report:

a. Total amount approved Rs. : 1,55,000/-( two years)

b. Total expenditure Rs. : 1,71,837/-

c. Report of the work done: Separate sheet is attached

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i. Brief objective of the project :

1) To synthesize NiCuZn ferrites which are the single most ferrite

requirements for MLCI application by autocombustion method using

glycine as the chelating agent.

2) Terbium(Tb3+) has high magnetic moment of 10.6 Bohr magnetons and

hence the substitution of Tb3+ should enhance the properties of ferrites.

3) To characterize the samples by X-Ray diffraction,SEM, and EDAX etc.

4) To study the dielectric properties of the ferrites.

ii. Work done so far and results achieved and publications, if any, resulting from

the work (Give details of the papers and names of the journals in which it has

been published or accepted for publication): Out of the work one paper

entitled “ Effect of Mg substitution on structural, infrared and dielectric

properties of NiCuZn ferrites” is published in the proceedings of

international conference held at International Conference on Magnetic

Materials and Applications (ICMAGMA) 2014 at Department of physics,

Pondichery University, Pondichery during September 15-17 2014. The

remaining work will be communicated to the international journals of

Physics and physical sciences.

iii. Has the progress been according to original plan of work and towards

achieving the objective. if not, state reasons: Yes

iv. please enclose a summary of the findings of the study. One bound copy of

thefinal report of work done may also be sent to the concerned Regional Office

of the UGC.: Enclosed bound copy of final report

v. Any other information:N/A


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Final Report of the work done

(First Year and second year)

First year:

1) Literature survey is done on the NiCuZn ferrites. The fabrication of spinel

structured ferrite nanoparticles has been intensively investigated in recent years

due to their unique physical and chemical properties and technological

applications in high density magnetic recording & MLCI. NiCuZn ferrites are

best suited for these applications.



The substitution of Tb3+ should enhance the magnetic properties of the ferrites.

Later on the characterizations are carried out to confirm the spinel ferrite

formation.

2) The said ferrites were synthesized as follows. A series of six samples with

general formula Ni0.25Cu0.30Zn0.45TbxFe2-xO4(x= 0.00,0.025,0.05,0.075,0.1 and

0.125) was prepared by autocombustion method using glycine as the fuel.

Stoichiometric ratios of AR grade (Ni(NO3)2.6H2O), (Tb(NO3)3.5H2O),

(Cu(NO3)2.5H2O), (Zn(NO3)2.6H2O) and (Fe(NO3)2.9H2O)(99.9% pure Aldrich)

were mixed with glycine(sd fine) in distilled water to prepare the precursor

solution [10]. The solution when heated on an electric heater at 500oC formed a

gel and then ignited in a self propagating combustion to form a fluffy powder

ash. The powder was then grinded and presintered at 650oC for four hours. For

DC resistivity and dielectric measurements,cylindrical disc shaped pellets of the

samples were prepared by using a Hydraulic press machine and applying

pressure of 10 tons/m2 for five minutes to the mixture of granulated fine powder

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mixed with PVA as binder. The pellets were finally sintered at 900oC for two

hours and used for XRD and FTIR characterization.

3) Prepared ferrites were characterized using XRD spectra, SEM and EDAX.

Second year:

1) The sintered ferrites were subjected to FTIR analysis. This confirms the

inverse spinel structure of Tb3+ substituted NiCuZn ferrites.

2) Dielectric measurements are done, the dielectric parameters confirm

dielectric dispersion with frequency. This shows normal ferrimagnetic behavior.

3) Vibrating Sample Magnetometer (VSM) measurements are used to calculate

the Saturation Magnetization(MS) and Cohersive field (Hc).

4) The investigated work is communicated to international journals of repute.

Principal Investigator Principal

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Annexure – VII




PROFORMA FOR SUBMISSION OF INFORMATION AT THE TIME OF SENDING

THE FINAL REPORT OF THE WORK DONE ON THE PROJECT

1. Title of the Project: “Influence of Tb3+ Substitution on Structural and

Electromagnetic properties of NiCuZn Spinel Ferrites”

2. NAME AND ADDRESS OF THE PRINCIPAL INVESTIGATOR: Smt.S.M.Kabbur

Department of Physics, Shri Shivaji Mahavidyalaya Barshi

3. NAME AND ADDRESS OF THE INSTITUTION :Shri Shivaji Mahavidyalaya Barshi,

Dist: Solapur 413411.

4. UGC APPROVAL LETTER NO. AND DATE: 47-462/12(WRO), dated 15/03/2013.

5. DATE OF IMPLEMENTATION: 15/03/2013

6. TENURE OF THE PROJECT: Two years(15/03/2013 to 14/03/2015)

7. TOTAL GRANT ALLOCATED : 1,55,000/-

8. TOTAL GRANT RECEIVED: 1,30,000/-

9. FINAL EXPENDITURE : 1,71,837/-

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10. TITLE OF THE PROJECT : “Influence of Tb3+ Substitution on Structural and

Electromagnetic properties of NiCuZn Spinel Ferrites”

11. OBJECTIVES OF THE PROJECT :

a. To synthesize NiCuZn ferrites which are the single most ferrite requirements

for MLCI application by autocombustion method using glycine as the

chelating agent.

b. Terbium(Tb3+) has high magnetic moment of 10.6 Bohr magnetons and hence

the substitution of Tb3+ should enhance the properties of ferrites.

c. To characterize the samples by X-Ray diffraction,SEM, and EDX etc.

d. To study the dielectric properties of the ferrites.

e. To study magnetic properties.

12. WHETHER OBJECTIVES WERE ACHIEVED (GIVE DETAILS):

Yes, the objectives were achieved as per the plan of the work to our

satisfaction.

1. Initially the survey of recent advances in relevant literature of NiCuZn

ferrites and rare earth substituted ferrites to enhance the magnetic and

structural properties was carried out with the help of internet, recent

books and journals on the subject.

2. This survey helped us to proceed with the problem. e.g. “Influence of Tb3+

Substitution on structural and electromagnetic properties of NiCuZn

spinel ferrites”.

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3. The new simple, rapid and cost effective synthesis by auto combustion

was used to synthesize the spinel ferrites using glycine as the reducing

agent.

4. Low sintering temperature of 900oC was achieved which is a prerequisite for

MLCI applications.

5. SEM analysis exhibits uniform grain size , nanoparticle size has been

confirmed by the XRD studies.

6. FTIR studies confirm inverse spinel ferrite structure and phase

transitions.

7. Study of magnetic and electrical properties of sintered ferrites.

12. ACHIEVEMENTS FROM THE PROJECT:-

One of the aims of this research project was to synthesize NiCuZn

ferrites suitable for MLCI applications.Magnetic nanoparticles exhibiting

supermagnetic behavior display little or no remanant magnetization and

coercivity while keeping very high saturation magnetization and high

permeability.Rare earth substituted different ferrites are becoming promising

materials for various applications because they give rise to better electrical

magnetic and structural properties depending upon the type and amount of rare

earth ion. The substitution of rare earth ions into the ferrite led to the

replacement of Fe3+ by rare earth ions and indicate structural changes along

with dielectric and magnetic manifestations.

By the sol-gel auto combustion method, the desired ferrites were

synthesized so that low temperature sintering can be achieved. AR grade metal

nitrates were mixed in stoichiometric proportion and glycine was used as the

chelating agent. The presintering was done for 650 o C for 4h. The calcined

ferrite powder was granulated, the pellets were formed by using uniaxial

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hydraulic press(10 tons/m2+) for five minutes and then finally sintered for

900oC for 2h. The study also includes characterization by standard methods and

also study of dielectric and magnetic properties.

14. SUMMARY OF THE FINDINGS ( IN 500 WORDS ):

The main objective of this work was to synthesize NiCuZn ferrites with

Terbium substitution as the trivalent ion by using auto combustion method

using glycine as the chelating agent. Terbium has a high magnetic moment

hence it was the subject of investigation. Characterization was carried out using

XRD,SEM,EDX,FTIR,Magnetization studies and dielectric parameters.

1. SYNTHESIS:

Synthesis of trivalent doped NiCuZn ferrites by sol-gel autocombustion

method using glycine as the reducing agent. Metal nitrates are used as the

starting materials. Low sintering temperature of 900o C is achieved which is

very essential for MLCI applications.

2. X-RAY DIFFRACTION STUDIES:

X-Ray diffraction studies show primary peaks like (111), (220), (310), (311),

(222), (400), (511), (333) and (440) which match well with inverse spinel

structure in accordance with JCPDS card No. 48-0490. The lattice parameter

varies between 8.387 Ao to 8.403 Ao. The crystallite size D is found to vary

between 28.65 nm to 35.67 nm. 3. SCANNING ELECTRON MICROSCOPE ANALYSIS:

The SEM micrographs exhibit inhomogenous grain size distribution. With

the increase of Terbium concentration the grain size was found to decrease

578 nm to 346 nm. The decrease in the grain size can be explained on the basis

of ionic radii of the terbium ions (0.93 Ao). It is assumed that some of the

Terbium ions may reside on the grain boundaries, these can hinder the growth

and also exert stress on the grains which causes the reduction of grain size.

4. EDX STUDIES:

The Energy-dispersive X-ray spectroscopy which is an analytical

technique used for the elemental analysis or chemical characterization of a

sample. It is found that elemental percentage of Tb3+ varies between 0.86 % to

2.50%, hence confirming the substitution of rare earth ions.

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5. FTIR STUDIES:

FTIR absorption spectra recorded between 400-1600 cm-1 for the various

ferrite compositions. The difference in positions of the bands arises due to

differences in the distances for the octahedral and tetrahedral ions. The high

frequency band υ1 lies in the range 712-721 cm -1 while the low frequency band

υ2 lies in the range 495-508 cm-1. According to the study of vibration spectra by

Waldron, the υ1 band arises due to intrinsic vibrations of the tetrahedral groups

and υ2 band due to the instrinsic vibrations of octahedral groups. The change in

the band positions of υ1 and υ2 is because of change in the bond length of Fe3+ -

O2- at tetrahedral (0.189 nm) and octahedral (0.199 nm) sites respectively.

6. DIELECTRIC MEASUREMENTS:

The dielectric measurements show normal ferromagnetic behavior. For the

ferrites, ε׳and ε׳׳decrease with frequency. This observed dielectric behavior can

be explained based on space charge polarization theory and hopping model. The

presence of Fe3+ and Fe2+ ions make ferrite materials to exhibit dipolar

polarization.

7. SATURATION MAGNETISATION (MS) AND COERCIVITY (HC):

The magnetic parameters like saturation magnetization (MS) and Coercivity

(Hc) are calculated from th MH loops . MS varies between 43.25 emu/gm to

53.46 emu/gm for the various samples. The coercivity HC varies between 590.3

to 400.1 Oe.

8. AC Resistivity

The AC resistivity of the ferrites is calculated with the relation, ρac =

where R is the resistance of the specimen in Ohms, A is area of crosssection and

t is the thickness. Figure 22. shows the variation of log ρac →log frequency.

The AC electrical resistivity showed decreasing trend with increasing

frequency.

16. WHETHER ANY PH.D. ENROLLED/PRODUCED OUT OF THE PROJECT: N/A

17. NO. OF PUBLICATIONS OUT OF THE PROJECT : one (publication is attached)


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CHAPTER I

Introduction

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I. INTRODUCTION:

The study of ferrites has attracted immense attention of the scientific

community because of their novel properties and technological applications

especially when the size of the particles approaches to nanometer scale[1]. More

novel electrical and magnetic behaviors have been observed in comparison with

their bulk counterpart [2]. In general, the transport properties of the

nanomaterials are predominantly controlled by the grain boundaries than by the

grain itself [3]. Due to this reason, the magnetic materials have explored a wide

range of applications and thus are replacing conventional materials.

In the last two decades, latest advancement in wireless technology has

explored the area of real-time communication. Internet-accessible cell phones

and high-speed wireless local area network are the best examples of this

technology. The core of these systems is based on a radio frequency [RF] circuit

consisting of transmission and receiving circuit blocks required in signal

amplification, filtering, and modulation that in turn require hundreds of passive

chip components such as capacitors and inductors. Inductors adapted to RF

circuits of mobile devices are mostly multilayer chip inductors [MLCIs] and

microspiral inductors. MLCIs were developed in the 1980s by thick film

printing and co-firing technologies using low temperature-sintered Ni-Cu-Zn

ferrite and Ag. Recently, Ni-Cu-Zn ferrites have been developed to meet a

http://www.nanoscalereslett.com/content/7/1/112#B3

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demand for miniaturization of electronic components [4,5]. The ferrite powder

needs to be sintered below 950°C in order to co-heat with silver internal

electrodes (Tm approximately 962°C) and should have low dielectric constants

for MLCI application. Materials with high permeability are also required for

reducing the number of layers in MLCIs and for realizing the better

miniaturization [6]. Further, ferrite nanoparticles are commercially important

for several applications such as in electromagnetic devices operating at radio

frequencies where the superparamagnetic [SPM] properties have a strong

influence in enhancing their quality of applications [7-9]. Nanoparticles of these

materials exhibit interesting phase transitions from SPM state to

ferri/ferromagnetic state or vice versa with a variation of temperature depending

on their sizes. In this ferrite nanoparticle system, the Cu content of the

compositions was kept constant at 30% of the A site (AB2O4 spinel);

nonmagnetic Zn2+ ions occupy the tetrahedral A sites, replacing Fe3+ ions, which

eventually go to octahedral B sites. Hence, zinc cations magnetically dilute the

system by making the A-B exchange interaction relatively weaker. This weaker

coupling reduces the anisotropy energy of the system, which facilitates the onset

of SPM relaxation in bigger size particles even at room temperature.

Many reports are available in the literature on Ni-Cu ferrites where

people have reported various properties of the studied ferrite material in bulk as






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well as in nanoscale form. Chakrabarti et al.[10] studied the magnetic properties

of nanocrystalline Ni0.2Zn0.6Cu0.2Fe2O4 prepared using a chemical route method,

and they reported that below 80 K, the nanoparticles exhibit

superparamagnetism, and the saturation magnetization increases with increasing

particle size. Seong et al. [11] investigated the structural and electrical

properties of Cu-substituted Ni-Zn ferrites, and they have reported that the

alternating current (ac) conductivity increases with increasing temperature of

the sample and frequency of the applied field. Roy et al. [12] reported the effect

of Mg substitution on electromagnetic properties of

(Ni0.25Cu0.20Zn0.55)Fe2O4 ferrite prepared through auto-combustion method, and

they found that the permeability and ac resistivity increased while the magnetic

loss decreased with the progressive substitution. Jadhav et al. [13] reported the

structural, electrical, and magnetic properties of Ni-Cu-Zn ferrite synthesized by

citrate precursor method, and they reported that the dielectric parameters

decrease with increasing frequency of the applied field. They further report that

the maximum value of the saturation magnetization was found for 20% Cu

doping.

However, as per our best search, we have not found any detailed report in

the literature on the Electromagnetic properties of trivalent substituted NiCuZn

Fe2O4 ferrite nanoparticles. Therefore, keeping in view the high demand and





2

28

importance of magnetic ferrite nanoparticles, we propose to work on properties

of nanocrystalline Ni-Cu-Zn ferrites.

NiCuZn ferrites are the most important magnetic materials used for

the manufacturing of Multi Layer Chip Inductor (MLCI).

Recently the industry of electronic components is in continuous pursuit

of miniaturization, light weight, high performance, multifunctioning, high

density, high resolution, higher switching speed etc. Surface Mounting (SMT)

technique has progressed tremendously. The reason is that SMT has been

widely adapted instead of the insertion system of leaded components because of

better response, selectivity and feasibility for practical use. NiCuZn ferrites

have better magnetic properties at high frequency and low sintering

temperature. Materials with high permeability are required for reducing the

number of layers in MLCI.

In the present investigative work we wish to carry out studies on

NiCuZn ferrites and trivalent substitution of Tb3+ on the same composition of

ferrites. The synthesis will be done by using chemical method rather than the

earlier ceramic method. In ceramic method coarse particle size and unwanted

crystalline aggregation of the material particles takes place. In chemical

method pure and single phase nanoparticles which yield high density magnetic

materials can be obtained [14].

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29

Sol–Gel Autocombustion method:

It is inexpensive and has low external energy consumption . It produces

nanosized, homogenous, highly reactive powders using simple methodology

and simple equipment. Combustion synthesis proceeds through a highly

exothermic redox reaction between nitrates and organic fuel like glycine[15].

This ensures more homogeneity.

SIGNIFICANCE OF THE RESEARCH WORK:

The fabrication of spinel structured ferrite nanoparticles has been

intensively investigated in recent years due to their unique physical and

chemical properties and technological applications in high density magnetic

recording & MLCI. NiCuZn ferrites are best suited for these applications.



The rare earth Lanthanides possess good magnetic moment, hence we

intend to substitute Tb 3+ for the Fe3+ ion. This should enhance the magnetic

properties of the ferrites.

NiCuZn ferrite have been synthesized through solid state method by

manyinvestigators [16,17]. In this method, different metal oxides are mixed and

calcined to get ferrite powders. However, mechanical mixing of different oxides

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30

is hardly intimate and homogeneous and hence it results in composition

fluctuation at every stage of processing that also persists after sintering . Solid

state process requires calcination temperature more than 750°C for phase

formation and sintering temperature more than 1000°C to achieve better

densification. At this high sintering temperature, evaporation of Zn leads to the

formation of chemically inhomogeneous material [18]. Chemical methods

overcome the limitations of the ceramic method :Co-precipitation process was

used for synthesis of NiCuZn ferrites by many researchers and they

obtained crystalline ferrite particles with particle size of about 30 nm.

Co-precipitation method:

Ghodake et al. [19] reported the synthesis of (NixZntCu(1-t)-x))Fe2O4 ferrites

by co-precipitation technique using oxalate precursors. Sol-gel method was used

to synthesis the ferrite by P.K.Roy et al[12].

Z. Yue et al. [20] observed nano-sized spherical NiCuZn ferrite having

particle size 10-20 nm by this method.These chemical methods have some

disadvantages. They, have multiple step pathways that are time consuming,

require expensive alkoxide precursor material and are highly pH sensitive which

require special attention for complex systems like NiCuZn ferrites. The auto

combustion method has the advantages of using inexpensive precursors and low

external energy consumption and resulting nano-sized, homogeneous, highly

2

31

reactive powder. Several researchers prepared NiCuZn ferrite including

various other ferrites like MgCuZn , MgCu and NiZn by auto combustion

method to produce nano precursor. Generally, metal nitrate salts are used as

reactant and glycine, urea and citric acid are used as fuel in auto combustion

method. Auto combustion process has been proved to be a simple and

economic way to prepare nanoscale ferrite powders . Nano-structured materials

offer novel properties. It decreases the free energy during sintering due to

increasing surface area which is the main driving force for lowering the

sintering temperature of particles. By proper tuning of the particle size, it is

possible to optimize the desired properties like electrical, magnetic, optical,

thermal, mechanical etc.

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32

References:

1. Subhash C, Srivastava BK, Anjali K: INDIAN J. PURE APPL.

PHYS. 2004, 42:366-367.

2. Kittle C: PHYS. REV. 1948, 73:810-811.

3. Kale A, Gubbala S, Misara RDK: J. MAGN. MAGN.

MATER. 2004, 3:350-358.

4. Kim KY, Kim WS, Ju YD, Jung HJ: J. MATER. SCI. 1992, 27:4741-

4745.

5. Fujimoto M: J. AMERICAN CERAM. SOC. 1994, 77:2873-2878.

6. Qi XW, Zhou J, Yue Z, Gui ZL, Li LT: J. MAGN. MAGN.

MATER. 2002, 251:316-322.

7. Nakamura T: J. APPL. PHYS. 2000, 88:348-353.

8. Kim WC, Kim SJ, Lee SW, Kim CS: J. MAGN. MAGN.

MATER. 2001, 226:1418-1420.

9. Yue ZX, Zhou J, Wang XH, Gui ZL, Lee LT: J. MATER. SCI.

LETT. 2001, 20:1327-1329.

10. Chakrabarti PK, Nath BK, Brahma S, Das S, Goswami K, Kumar U,

Mukhopadhyay PK, Das D, Ammar M, Mnzaleyrat F: J. PHYS.

CONDEN. MATER. 2006, 18:5253-5267.

11. Seong KC, Hassan J, Hashim M, Mohd W, Yusoff DW: SOL. STAT.

SCI. TECH. 2006, 1:134-140.

http://www.nanoscalereslett.com/sfx_links?ui=1556-276X-7-112&bibl=B1









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12. Roy PK, Bera J: J. MAGN. MAGN. MATER. 2006, 298:38-42.

13. Jadhav PA, Devan RS, Kolekar YD, Chougule B.K: J. PHYS. CHEM.

SOL. 2009, 70:396-400.

14. Sattar AA: EGPTIAN. J. SOL 2004, 27:99-110.

15. P.K. Patre, A.R. Kulkarni., S.M. Gupta & C.S. Harendranath, Physica B:

condensed matter, vol-400, No. 1-2, (2007), pp 237-242.

16. J.H. Jean, C.H.Lee, W.S.Kou, J.Am.ceram.Soc 82(2)(1999), 343

17. J.Z. Msomi, T.Moyo, T.B. Doyle, J.Magn.Magn. mater 310 (2007)

2534.

18. K.C. Patil, S.S. Manoharan, D.Gajpathy, “Preparation of high density

ferrites”, in Handbook of Ceramics and Composites”, vol 1.,New York :

Marcel Decker (1990), 469.

19. S.A. Ghodake, U.R. Ghodake, S.R.Sawant, S.S. Suryavanshi, J. Magn

Magn Mater 305(1)(2006).

20. Z.YUE., J. Zhou., L.Li, H.Zang, Z.Gui, J. Magn.Magn.Mater,

208(2000)55.




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34

CHAPTER II

Experimental Details

Synthesis and Characterization

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35

EXPERIMENTAL DETAILS:

1.MATERIAL SYNTHESIS:

A series of six samples with general formula Ni0.25Cu0.30Zn0.45TbxFe2-xO4(x=

0.00,0.025,0.05,0.075,0.1 and 0.125) was prepared by autocombustion method

using glycine as the fuel. Stoichiometric ratios of AR grade (Ni(NO3)2.6H2O),

(Tb(NO3)3.5H2O), (Cu(NO3)2.5H2O), (Zn(NO3)2.6H2O) and

(Fe(NO3)2.9H2O)(99.9% pure Aldrich) were mixed with glycine(sd fine) in

distilled water to prepare the precursor solution . The solution when heated on

an electric heater at 500oC formed a gel and then ignited in a self propagating

combustion to form a fluffy powder ash. The powder was then grinded and

presintered at 650oC for four hours. For DC resistivity and dielectric

measurements,cylindrical disc shaped pellets of the samples were prepared by

using a hydraulic press machine and applying pressure of 10 tons/m2 for five

minutes to the mixture of granulated fine powder mixed with PVA as binder.

The pellets were finally sintered at 900oC for two hours and used for XRD and

FTIR characterization.

2) CHARACTERIZATION:

i) XRD analysis

The crystallite phases of the synthesized ferrites were identified by X-ray

Diffraction spectroscopy using CuKα radiation with wavelength (λ = 1.5406AO).

The most intense peaks in all the ferrite compositions indexed as

(111),(220),(310),(311),(222),(400),(511),(333) and (440) which match well

with inverse spinel structure in accordance with JCPDS card No. 48-0490. are

found to match well with single-phase cubic spinel structure.

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36

ii) SEM and EDX analysis

The SEM images are analysed to calculate the grain size and EDAX

measurements confirm the percentage of the elements which go into the ferrite

samples.

iii) FTIR spectroscopy

IR Perkin Elmer FTIR spectrometer was used to record IR spectra at

room temperature over the range 400-1600 cm-1. The samples for recording the

spectra were prepared in the form of pellets in KBr medium.

iv) DC resistivity

The DC resistivity was measured using two probe method, a calibrated

thermocouple was used to measure the temperatures, the variation of ρdc with

temperature was analysed. High resistivities of ferrites are desirable to make

them applicable in Surface Mounting Devices and an attempt is made to study

the effect of Tb3+ in NiCuZn semicounducting magnetic oxides.

v) Dielectric measurements

The dielectric properties and AC resistivities were measured at room

temperature in the range 20 Hz to 1 MHz using LCR meter (model HP 4284A).

Parallel capacitance and dielectric loss tangent were measured and the dielectric

parameters calculated as a function of frequency. AC resistivity was measured

for all the compositions with varying frequency at room temperature.

vi) VSM Analysis

The saturation magnetisation (MS) and Coercivity (HC) can be analysed from

the Vibrating Sample Magnetometer method.

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vii) AC resistivity

AC resistivity is an important property of low temperature sintered

NiCuZn ferrites for MLCI applications. The AC resistivity for all the samples is

measured at room temperature between the frequency range (20Hz – 1MHz)

using LCR –Q meter bridge (model HP 4284) and the relation:

AC =

where R is resistance in ohms, A is area of crosssection and t is the thickness.

The AC electrical resistivity showed decreasing trend with increasing

frequency. As the applied frequency increases there is an increased probability

for jumping of electron through Fe3+↔ Fe2+ ions. The increased

concentration of Fe2+ ions induces electron hopping Fe3+↔ Fe2+ at B sites

thereby reducing resistivity. The inverse relationship of dielectric constant with

square root of resistivity is evidenced through the observations

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CHAPTER III

Results and discussion

2

39

1. X-ray diffraction analysis

XRD patterns of Ni0.25Cu0.30Zn0.45TbxFe2-xO4(x= 0.00,0.025,0.05,0.075,0.1

and 0.125)are recorded. The X-ray peaks are shown in Fig.1. The most intense

peaks in all the specimens indexed as

(111),(220),(310)(311),(222),(400),(511),(333), and (440) These identifications

are found to match well with single-phase cubic spinel structure (JCPDS card

no. 48-0490). The lattice parameters (a) of the samples are determined using

the Eq. (1)

(1)

The lattice parameter (a) increases from 8.354 Å to 8.403 Å. This can be

explained on the basis of consideration of ionic radii. The ionic radius of Tb3+

(0.93Å) is more than that of Fe3+ (0.64 Å), hence Tb3+ enters into the spinel

lattice and the size of unit cell increases[1]. The crystallite size (D) was

determined from the diffraction peak broadening using Debye-Scherrer’s Eq.

(2) [2-4].

Cosθ β

0.9λD

(2)

where D is crystallite size in nm, λ is the wavelength of CuKα radiation, β is the

full width at half maximum in radians and θ is the Bragg’s angle of diffraction,

here the peak broadening of highest peak (311) is used[2]. The crystallite size D

varies from 28.65 nm to 35.67 nm, which are in good agreement with values

reported by . The variation of lattice constant(a) and crystallite size(D) with

Terbium content is shown in Fig.2. The theoretical X-ray density[3] for the

samples having spinel structure with 8 molecules per unit cell was calculated

using the Eq.(3):

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D = (3)

where M is the molecular weight, N is Avagadro number (N = 6.02214x1023

mole-1) and a is the lattice parameter[4]. X-ray density was observed to be

greater than the bulk density, but both are showing increasing trend with Tb

additive, this can be attributed to high atomic weight of Tb (158.925a.m.u)

compared to Fe (55.845 a.m.u.) and also high density of Tb (8.540 gm/cm3) as

compared to Ni (7.874gm/cm3). The variation of X-ray density(dXRD) and bulk

density(dbulk) with content of Tb is shown in Fig.3.

To measure the densities of the ferrite samples, liquid immersion

technique based on Archimedes principle with Xylene as the medium is

used.The weight of sample in air and in xylene were recorded separately using a

single pan digital balance and the bulk density (dbulk) was calculated using the

relation:

dbulk (4)

where w is the weight of sample in air, is the weight of sample in xylene and

is the density of xylene. The percentage porosities of the ferrite samples

were calculated using the relation:

P = (1 – ) × 100 (5)

There is increase in the porosity of ferrite samples indicating crystal

imperfections. The difference in the two densities arises due to the pores in the

crystal formation which depends on stoichiometry, method of preparation, heat

treatment conditions etc[5].

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Table 1

Compositional variation of lattice parameter(a),average crystallite

size(D), Xray density(dXRD),bulk density(dbulk), percentage

porosity(P),tetrahedral bond length(LA), and octahedral bond length(LB)

Tb

Content(x)

Lattice

Parameter(a)

A

Crystallite

Size(D)

µm

X-ray

density

dXRD

gm/cc

Bulk

density

dbulk

gm/cc

Porosity(p)

%

Tetrahedral

bond

length(LA)

A

Octahedral

Bond

length(LB)

A

0.00 8.387 57.8 5.54 4.83 8.50 7.285 4.178

0.025 8.390 52.9 5.58 4.85 9.84 7.306 4.183

0.050 8.393 48.9 5.60 4.89 11.34 7.403 4.196

0.075 8.396 43.9 5.63 4.93 12.05 7.493 4.203

0.100 8.399 39.2 5.68 4.99 12.46 7.502 4.261

0.125 8.403 34.6 5.71 5.02 14.46 7.536 4.352

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Fig. 1. X-ray diffractograms of Ni0.25Cu0.30Zn0.45TbxFe2-xO4

ferrites

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Fig.2 Compositional variation of Lattice parameter(a) and average

crystallite size(D) of Ni0.25Cu0.30Zn0.45TbxFe2-xO4 ferrites

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44

Fig. 3. Compositional variation of X-ray density(dXRD) and bulk

density(dbulk) of Ni0.25Cu0.30Zn0.45TbxFe2-xO4

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2. SCANNING ELECTRON MICROSCOPY

The understanding and control of microstructure in polycrystalline

materials for example metal ceramics is important technologically. Since such

key properties like mechanical strength, electrical conductivity, magnetic

susceptibility etc. are strong functions of the average grain size, porosity and

range of grain sizes. This microstructure is in turn a direct consequence of the

grain growth mechanism.

Most of the magnetic properties and characteristics of polycrystalline

magnetic materials are microstructure sensitive. That can be illustrated by

numerous examples, if just to mention some of the most impressive ones,

hysteresis loop with its coercivity and remenance, permeability mainly its part

related to the domain wall motion, magnetic dispersion spectra with their

various resonance and relaxations, the energy loss at low and high excitation

levels in all frequency ranges.

The dielectric permittivity of polycrystalline ferrites is related to the

average grain size for specimens of the same compositions. For finding the

average grain size, SEM micrographs of all compositions were taken using a

well polished pellet surface. The average grain size has been evaluated by using

the method given below. From SEM micrographs of various compositions

average grain size and spatial features of granular structure are studied.

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From SEM photographs, the average grain size D is calculated as follows.

i) Draw a diagonal on the photograph

ii) Measure the maximum unidirectional particle size in the vertical direction

against the diagonal.

iii) Average out the maximum unidirectional particle size.

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Fig. 4. Scanning Electron Micrograph of Ni0.25Cu0.30Zn0.45Fe2O4 ferrite

2

48

Fig. 5. Scanning Electron Micrograph of Ni0.25Cu0.30Zn0.45Tb0.025Fe1.975O4

ferrite

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ferrite

2

50


ferrite

2

51


ferrite

2

52


ferrite

2

53

Table 2

Compositional variation of average grain size of Ni0.25Cu0.30Zn0.45TbxFe2-xO4

ferrites

Tb content(x)

Average

grain

size(d) nm

0.00 578.3

0.025 536.6

0.05 512.3

0.075 506.7

0.10 483.1

0.125 346.5

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3. Energy Dispersive Absorption Spectroscopy(EDX)

Energy-dispersive X-ray spectroscopy (EDS, EDX, or XEDS),

sometimes called energy dispersive X-ray analysis (EDXA) or energy

dispersive X-ray microanalysis (EDXMA), is an analytical technique

used for the elemental analysis or chemical characterization of a sample.

It relies on an interaction of some source of X-ray excitation and a

sample.

It is found that elemental percentage of Tb3+ varies between 0.86 % to

2.5%, hence confirming the substitution of rare earth ions.

Table 3 Elemental Percentage in Ni0.25-xCu0.30Zn0.45 TbxFe2-xO4

x=0.00,0.025,0.050.075,0.100,0.125

Tb content(x) Ni2+% Tb3+% Cu2+% Zn2+% Fe3+% O2-%

0.00 7.05 -- 8.99 6.18 69.35 7.93

0.025 6.23 0.86 9.74 6.17 68.48 8.52

0.050 4.72 1.31 10.95 11.30 65.75 5.97

0.075 1.40 3.47 9.90 6.36 69.11 9.76

0.100 3.69 2.41 9.06 7.59 68.51 8.74

0.125 0.16 2.50 9.90 6.08 74.69 6.67

https://en.wikipedia.org/wiki/Elemental_analysis

https://en.wikipedia.org/wiki/Characterization_(materials_science)

https://en.wikipedia.org/wiki/X-ray

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Fig.10. Energy Dispersive X-ray spectrograph of Ni0.25Cu0.30Zn0.45 TbxFe2-xO4

ferrite

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4.FOURIER TRANSFORM INFRA RED ANALYSIS.

FTIR spectra for the sintered samples showed two strong

frequency bands, υ1 (712-721 cm-1) and υ2 (495 - 508 cm-1) which are the

characteristic features of ferrites are shown in Fig. 7. The υ1 band is assigned to

the vibrations of the bond between the oxygen ion and the tetrahedral metal ion

O-Mtetra and the other band υ2 arises due to the vibrations of the bond between

the oxygen ion and the octahedral metal ion O-Mocta . The difference in the band

positions are observed in the spectra because of the change in the bond length

between Fe3+ - O2- ions for the tetrahedral and octahedral complexes. Both the

bands are broad indicating inverse spinel structure in which the Fe3+ ions are

distributed statistically at tetrahedral and octahedral sites based on the

stoichiometric composition. The slight variation in band positions of υ1 and υ2 is

affected by the method of preparation, grain size and heat treatment conditions .

Waldron [6] has given the force constants for tetrahedral site (kt) and

octahedral site (ko).The force constant is second order derivative of potential

energy w.r.t. site radius (rA and rB) and the other independent parameter being

kept constant:

kt = 7.62 × MA × × 10-3 dynes/m (6)

ko= 10.62 × MB × × 10-3 dynes/m (7)

The threshold energy values Eth can be calculated from Planck’s quantum

theory of radiation:

Eth = h f = h = h c υth (8)

where f is frequency of vibration, h is Planck’s constant in eV, h = 4.13x10-15

eV-sec, c is velocity of light and υth is threshold frequency in cm-1. According

to Waldron [28], the inflection point in the graph of transmittance versus wave

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number (Fig. 11) can be used to determine the threshold frequency υth for the

electronic transitions[7]. The calculated Eth values decrease with the content of

Tb3+. It has been reported that the broadening of band is commonly observed

when the system transfers from inverse spinel to normal spinel. The half band

width (ΓA) of tetrahedral sites show decreasing nature with increase in Tb3+.

The half band width (ΓB) of octahedral sites could not be determined because

the band terminated below the experimental limits. The compositional variation

of tetrahedral frequency (υ1),octahedral frequency (υ2), threshold frequency

(υth),threshold energy (Eth),tetrahedral force constant (kt) and octahedral force

constant (ko) for ferrites are given in Table 4.

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Table 4. Compositional data on tetrahedral frequency (υ1),octahedral

frequency (υ2),threshold frequency (υth),threshold energy (Eth),

tetrahedral force constant (kt),octahedral force constant (ko) for

Ni0.25Cu0.30Zn0.45 TbxFe2-xO4 ferrites.

Composition (x) 0.00 0.025 0.050 0.075 0.100 0.125

Tetrahedral frequency (υ1) cm-1 721 719 717 715 713 712

Octahedral frequency (υ2) cm-1 508 504 500 498 497 495

Threshold frequency (υth) cm-1 1387 1385 1384 1383 1382 1376

Threshold energy (Eth) eV 0.1724 0.1722 0.1712 0.1710 0.1699 0.1695

Tetrahedral force constant

(kt)x10-3 dynes/m

3.36 3.26 3.17 3.08 3.06 2.97

Octahedral force constant

(ko)x10-3 dynes/m

0.85 1.12 1.23 1.24 1.28 1.32

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Fig. 11. FTIR spectra of Ni0.25Cu0.30Zn0.45 TbxFe2-xO4 ferrites.

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5. DC resistivity(ρDC)

The DC electrical resistivity (ρDC) Ni0.25Cu0.30Zn0.45 TbxFe2-xO4

ferrites where (0.00 ≤ x ≤ 0.125) is measured as a function of temperature using

two probe method, a calibrated sensitive thermometer is used to measure the

temperature. The variations of log ρDC →1000/ToK for various ferrites are

shown in Fig.12[8]. The resistivity varies between 6.47x107 Ω-cm to 2.27x108

Ω-cm as Terbium content(x) increases at room temperature. This depends on

the resistivities of Tb3+ (1,150μΩ-m) and Fe3+ (58.4 nΩ-m) and also the ionic

radii of the two trivalent ions. The DC electrical resistivity is temperature

dependent function given by the Arrhenius relation[9-11]:

ρ = ρ0 exp ( ) (9)

where ρ0 is the temperature independent constant, Ea is the energy of activation,

kB is the Boltzmann’s constant and T is absolute temperature. Using

equation(9) the activation energies in the ferrimagnetic region(ΔEf) and in

paramagnetic region(ΔEp) are calculated. ΔEf which lie in the range(0.2118 eV

– 0.2539 eV) are smaller than ΔEp which lie in the range(0.2815 eV – 0.3548

eV). From Fig.12 it can be observed that the variation of ρDC is almost linear up

to the Curie temperature where a break occurs indicating magnetic ordering

transtition from ferrimagnetic to paramagnetic region[10-12]. There takes place

an exchange interaction between the inner and the outer electrons of the ions at

the A-B sublattice. The smaller activation energies arise due to impurity ions in

the low temperature ferrimagnetic region. The larger activation energies arise

due to polaron hopping in the high temperature paramagnetic region.The

activation energies above the Curie temperature indicate the electron hopping of

the Tb3+ ions[].The resistivity of the ferrite samples decreases with increase in

temperature indicating the semiconductor nature of the material which is due to

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increase in drift mobility of the charge carriers[13-16]. Verwey’s hopping

model explains the conduction mechanism in ferrites. The high temperature

region is due to the hopping of polarons [17-18]. Here the conduction is

attributed to the transfer of electrons between the ions of the same element

occurring in more than one valence state, and these have random distribution on

crystallographically equivalent lattice sites. The ferrites form closed packed

oxygen lattices with the cations over the tetrahedral (A) and octahedral (B) sites.

The separation between two metal ions residing on octahedral site is smaller

than the separation between a metal ion on octahedral site and ion on the

tetrahedral site. Hence the probability of electron hopping between octahedral

and tetrahedral site is very small as compared to the ions occurring on the

octahedral sites only. The electron hopping among the ions of the tetrahedral

sites is not possible as there are only Fe3+ ions. The Fe2+ ions reside only at the

octahedral sites. The hopping mechanism depends on the distance between the

metal ions and the mobility of the charge carriers[19]. The presence of Tb3+ ions

on the octahedral sites as confirmed in FTIR analysis increases the distance

between metal ions of the octahedral sites and enhances the electron transfer

between iron ions. Hence the conduction mechanism in Ni0.25Cu0.30Zn0.45

TbxFe2-xO4 (0.00 ≤ x ≤0.125) inverse spinels can be explained using hopping

mechanism.

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Fig.12. DC resistivity of Ni0.25Cu0.30Zn0.45 TbxFe2-xO4 ferrites

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63

6. Dielectric measurements

The dielectric constant Ԑˡ of the samples was calculated using the

relation: Ԑˡ = where cp is the capacitance in pF, t is the thickness of the

pellet in cm, A is the area of crosssection of the specimen and Ԑo = 8.854 x 10-2

pF/cm. The complex dielectric constant was calculated from the relation Ԑˡˡ = Ԑˡ

tan δ where tan δ = 1/Q , Q is the quality factor. Figure 13. shows variation of

dielectric constant (Ԑˡ) → log frequency and Figure 14. shows variation of

complex dielectric constant (Ԑˡˡ) → log frequency for the ferrites. Ԑˡ and Ԑˡˡ

decrease with frequency. This observed dielectric behavior can be explained in

the light of space charge polarization and hopping model[20]. The presence of

Fe3+ and Fe2+ ions render ferrite materials to exhibit dipolar polarization. The

dielectric polarization is also affected by factors such as structural

homogeneity, stoichiometry,density, grain size and porosity of the ferrites. The

rotational displacement of dipole results in orientational polarization. In ferrites,

rotation of Fe2+ to Fe3+ and vice versa can be visualized as the exchange of

electrons between two ions so that the dipoles align themselves with respect to

the applied field. The polarization at lower frequencies may result from electron

hopping between Fe3+↔ Fe2+ ions in the ferrite lattice . The polarization

decreases with increasing frequency and reaches a constant value due to the fact

that beyond a certain frequency of external field, the electron exchange Fe3+↔

Fe2+ cannot follow the changes in the applied field. Also the presence of

Ni3+/Ni2+ ions, which gives rise to p – type carriers, contributes to the net

polarization though it is small. The net polarization increases initially and then

decreases with increasing frequency . Figure.15 shows the variation of dielectric

loss factor(tan δ) with log frequency(20 Hz to 1 MHz) at room temperature.

The dielectric loss decreases with the increasing frequency which is a normal

behavior of any ferrite material. The dielectric loss decreases rapidly in the low

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frequency region while the rate of decrease is slow in the high frequency region

and it shows an almost frequency independent behavior in the high frequency

region. The low loss values at higher frequencies show the potential

applications of these materials in high frequency microwave devices [21] for

MLCI applications. The compositional data on dielectric parameters(Ԑʹ,Ԑʹʹ, and

tan δ) and ρac at 1KHz is given in Table 5.

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Table 5

Data on dielectric constant (Ԑˡ),complex dielectric constant(Ԑˡˡ),dieletric

loss tangent (tan δ), AC Resistivity (ρac) of Ni0.25Cu0.30Zn0.45 TbxFe2-xO4

ferrite system at 1 kHz

Composition

(x)

Ԑ| Ԑ|| Tan δ ρac

x 106 Ω-cm

Porosity

%

0.000 24.219 9.637 0.415 27.259 10.97

0.025 21.315 7.793 0.365 26.900 12.37

0.050 24.311 6.539 0.269 10.169 14.51

0.075 46.725 13.671 0.299 7.029 19.23

0.100 42.060 10.024 0.255 1.064 26.16

0.125 41.499 16.072 0.446 1.281 31.02

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Fig.13. Variation of dielectric constant (ε′) of

Ni0.25Cu0.30Zn0.45 TbxFe2-xO4

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Fig.14. Variation of complex dielectric constant (ε′′) of


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Fig.15. Variation of dielectric loss factor (tanδ) of


7.Vibrating Sample Magnetometer measurements (VSM)

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The magnetic parameters such as saturation magnetization(MS), retentivity(Mr)

and coercive field(Hc) were obtained from the VSM measurements and the

magnetic moment is calculated using the relation[22]:

nB= (10)

where M is the molecular weight of the ferrite sample, 5585 is the magnetic

factor. VSM measurements are done at low temperature of 80 K, because there

is more orderly alignment of spins at that temperature than at room

temperature.The hysteresis loops of Ni0.25Cu0.30Zn0.45 TbxFe2-xO4 ferrites are

shown in Figs.16-21.. The narrow magnetic hysteresis loops of the samples

indicate that the samples are magnetically soft with low coercivity. The increase

in MS can be explained on the basis of magnetic moment of Tb3+(10.3µB) and

Fe3+(5µB). The values of Bohr magneton(nB) increases with increase in Tb3+ .

This is because the A-B exchange interaction becomes strong due to

replacement of Fe3+ ions by Tb3+ ions at the respective sites. The increase in MS

and nB can be explained on the basis of Yafet-Kittel (Y-K) angle. The Y-K

angle is calculated from MS and nB as given in relation.

The magnetization values(MS) increase with increasing Tb3+ content. The

net magnetic moment(nB), the Y-K angle(αY-K) , the magnetic moment of

sublattice A(MA) and magnetic moment of sublattice B(MB) are related by the

expression:

nB = MBCos αY-K - MA (11)

It is observed that with the increase in Tb3+ content there is decrease in αY-K

angle, hence there is additional canting at the A and B sites. The inter-sublattice

superexchange interactions of the cations on the (A-B) site are much stronger

than the (A-A) and (B-B) intra sublattice exchange interactions. The preferential

occupancy of Mg2+ ions to the tetrahedral and octahedral sites in the ferrite

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sample results in decreasing the concentration of Fe3+ ions in these sites

reducing the B-B exchange interactions and consequently reducing the (A-B)

super-exchange interactions. Hence the main contribution of magnetic

properties derives from the highly magnetic Fe3+ ions(magnetic moment is

fixed to be +5µB )spin only present in the B-sites. The successive replacement

of Fe3+ ions by Tb3+ ions decreases the Fe3+

- Fe3+ (B-B) interaction.

The coercivity of the ferrites represents the strength of magnetic field

which is necessary to surpass the anisotropy barrier and allow the magnetization

of the nanoparticles following the magnetic field orientation. The coercivity

field (HC) decreases with the content of Tb3+ . Porosity has an effect on the

magnetization process because the pores work as a generator of demagnetizing

field. As the porosity increases, a higher field is needed to push the domain wall

thereby increasing HC. A crystalline field distortion can lead to internal stress

contributing to the anisotropy.

By considering the appropriate stoichiometry of the composition of ferrites

and the theoretical end values of anisotropy constant(K1) for FeFe2O4[23](-

12x104 erg/cm3) , the anisotropy constants(K1) of the ferrite samples are

calculated.

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Fig. 16. Hystersis curve of Ni0.25Cu0.30Zn0.45 Fe2O4 ferrite

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Fig. 17. Hystersis curve of Ni0.25Cu0.30Zn0.45Tb0.025 Fe1.975O4 ferrite

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Table 6. Compositional variation of saturation magnetization(MS),

remenant magnetization(Mr),Coercivity(HC),anisotropy constant(K1) and

Yafet-Kittel angle (αY-K)

Tb

content(x)

Saturation

Magnetization(M)

(80K) emu/gm

Remenant

Magnetization(Mr)

(80K) emu/gm

Coerciviy

(HC)Oe

Anisotropy

constant

(-K1x104)

Erg/cc

α(Y-K)

0.00 43.25 5.63 590.4 2.99 4234′23′′

0.025 45.21 6.88 488.5 2.98 4031′03′′

0.050 47.87 7.91 484.9 2.96 3724′13′′

0.075 49.67 8.23 480.5 2.95 3544′28′′

0.100 52.90 10.15 475.7 2.93 3234′13′′

0.125 53.46 11.5 400.1 2.92 3054′7′′

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8. AC Resistivity

The AC resistivity of the ferrites is calculated with the relation, ρac =

where R is the resistance of the specimen in Ohms, A is area of crosssection and

t is the thickness. Fig. 22. shows the variation of log ρac →log frequency. The

AC electrical resistivity showed decreasing trend with increasing frequency. As

the applied frequency increases there is an increased probability for jumping of

electron through Fe3+↔ Fe2+ ions. The increased concentration of Fe2+ ions

induces electron hopping Fe3+↔ Fe2+ at B sites thereby reducing resistivity. The

inverse relationship of dielectric constant with square root of resistivity is

evidenced through the observations. The AC resistivity in disordered crystallites

is a decreasing function of frequency. According to the hopping model, at low

frequency where the resistivity is constant, the transport takes place on infinite

paths. For a region of higher frequencies,where the resistivity strongly decreases

with frequency, the transport is dominated by contributions from hopping of

infinite clusters where the conduction mechanism would be due to hopping of

electrons between two Fe3+/Fe2+ ions at octahedral(B) sites in inverse spinel

lattice.

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Fig 22. Variation of AC resistivity log (ρac) with

log frequency for Ni0.25-xMgxCu0.30Zn0.45Fe2O4 ferrites

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References:

1) B.P.Jacob,S.Thankachan,S.Xavier,E.M.Mohammed, J. of Alloys and

Compds.541(2012) 29-35.

2) O.M. Hemeda, J. Magn.Magn.Mater.281 (2004) 36-41.

3) M.S. Khandekar, R.C. Kambale, S.S. Latthe, J.Y. Patil, P.A. Shaikh, N. Hur, S.S.

Suryavanshi, Mater.Lett.65 (2011) 2972-2974.

4) H.E. Scherrer, H. Kisker, H. Kronmuller, R. Wurschum, Nanostruct.Mater.6 (1995)

533-538.

5) B.D. Cullity, The Elements of X-ray Diffraction, Addison- Wesley Pub. Co. Inc.

London, 1956, p. 42.

6) R.D. Waldron, Phys. Rev. 99 (1955) 1727-1735.

7) K.B. Modi, S.J. Shah, N.B. Pujara, T.K. Pathak, N.H. Vasoya, I.J. Jhala, J. Molecular

Structure 1049 (2013) 250-262.

8) B.K. Labde, M.C. Sable, N.R. Shamkuwae, Mater.Lett.57 (2003) 1651-1655.

9) S.A. Patil, V.C. Mahajan, A.K. Ghatage, S.D. Lotke, Mater. Chem. Phys.57 (1998)

86-91.

10) C. Kittel, Introduction to Solid State Physics, 5thedition 1976, p.323.

11) B. Johnson, A.K. Walton, Brit. J. Applied Phys.16 (1965) p.475.

12) W.D. Callister, Materials Science and Engineering, An Introduction,4th edition, John

Wiley and sons 2000, p.714.

13) A. Kumar, Introduction to Solid State Physics, PHI learning private Ltd.2010, p.76.

14) E. J. W. Verwey, E.L. Heilmann, J. Chem. Phys. 15 (1947) 174.

15) M.S. Khandekar, R.C. Kamble, J.Y. Patil, Y.D. Kolekar, S.S. Suryavanshi, J. of

Alloys Compd. 509 (2011)1861-1865.

16) K.W. Wagner, Amer.Phis.40 (1913) 817-855.

17) M. Penchal Reddy, H Gon Kim, Dong Sun Yoo, W. Madhuri, N.R. Reddy, K.V. Siva

Kumar, R.R. Reddy, Mater. Sci and Appl.3 (2012) 628-632.

18) C.G. Koops, Phys. Rev. 83 (1951) 121-124.

19) D.A. Adler, J. Feinleib, Phys. Rev. B 2(1970) 3112-3119.

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20) S.S. Khot, N.S. Shinde, B.P. Ladgaonkar, B.B. kale, S.C. Watawe, Advances in Appl

Sci Research2 (4) (2011)460-471.

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Mater.407(2016)60-68.

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CHAPTER IV

Conclusions

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Conclusions:

i) The rare earth substitution of Tb3+ in NiCuZn ferrites was carried out to

study its effect on the structural, magnetic, electric and dielectric

properties.

ii) A novel, rapid and cost effective autocombustion method of ferrite

synthesis was used with glycine as the chelating agent. Glycine has a

high negative heat of combustion(-3.24kcal/gm) hence promotes the

redox reaction.

iii) Low sintering temperature of 900C was achieved which is an essential

prerequisite of NiCuZn ferrites for MLCI applications.

iv) XRD analysis confirms single phase cubic spinel structure, the lattice

parameter is found to vary in the range 8.387A - 8.403A .

v) The average crystallite size D is found to vary between 28.63nm to

35.67nm, nanocrystallite size is observed.

vi) The SEM analysis confirms inhomogenous grain growth, there is

porosity in the crystallite lattice indicating crystal imperfections.

vii) EDX measurements confirm the chemical composition of the ferrite,

the Terbium content lies in the range 0.86% to 8.00%.

viii) FTIR spectra shows inverse spinel formation and phase transition.

Two prominent bands υ1(712 – 721) cm-1 and υ2(495-508) cm-1

corresponding to tetrahedral and octahedral lattices. The υ1 band is

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assigned to the vibrations of the bond between the oxygen ion and the

tetrahedral metal ion O-Mtetra and the other band υ2 arises due to the

vibrations of the bond between the oxygen ion and the octahedral

metal ion O-Mocta.

ix) Dielectric properties show space charge polarization indicating ferrite

formation.

x) VSM measurements show narrow hysteresis loops indicating soft nature

of the magnetic oxides and low coercivity.

xi) AC resistivity shows frequency dispersion which can be explained based

on the conduction mechanism of charge carriers. The inverse

relationship of dielectric constant with square root of resistivity is

evidenced through the observations. The AC resistivity in disordered

crystallites is a decreasing function of frequency.

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ACKNOWLEDGEMENT

I am most thankful to University Grants Commission,

Western Regional Office Pune, for sanctioning and funding this

minor research project .

I express my sincere gratitude to trustees of

Shri Shivaji Shikshan Prasarak Mandal, Barshi and Late

Principal Dr. Madhukar Fartade, I/C Principal

Dr. P. R. Thorat for their support, kind co-operation and

continuous encouragement.

I am greatly indebted to Prof.S.S.Suryavanshi for his

invaluable guidance, encouragement and co-operation,

without whose help it would have been impossible to complete

this work. I am also thankful to Dr. U.R.Ghodake for his

support and continuous guidance in this research work. I also

take this opportunity to thank my colleagues of physics

department, Dr.R.R.Kothawale , Dr.S.D.Waghmare, Miss

S.R.Hublikar and Shri R.B.Attar for giving me help and support

throughout the work. I also thank Dr.V.M.Gurame for his

valuable suggestions while completing this work. I thank the

non teaching staff of physics department for their valuable

cooperation.

Smt. S.M.Kabbur

Documents

INFLUENCE OF Tb3+ SUBSTITUTION ON STRUCTURAL AND ... · 2 1 influence of tb3+ substitution on structural and electromagnetic properties of nicuzn spinel ferrites minor research project