Analysis of Eu 3+ Emission from Mg TiO Nanoparticles by ...downloads.hindawi.com/journals/acmp/2015/736517.pdf · 2 transition and with the emission decays varying between . and

Research ArticleAnalysis of Eu3+ Emission from Mg2TiO4Nanoparticles by Judd-Ofelt Theory

Katarina VukoviT Mina MediT Milica SekuliT and Miroslav D DramiTanin

Vinca Institute of Nuclear Sciences University of Belgrade PO Box 522 11000 Belgrade Serbia

Correspondence should be addressed to Miroslav D Dramicanin dramicanvincars

Received 5 May 2015 Revised 30 June 2015 Accepted 5 July 2015

Academic Editor Mohindar S Seehra

Copyright copy 2015 Katarina Vukovic et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

Eu3+ doped Mg2TiO4(2 at of Eu) nanoparticles which are 5 to 10 nm in diameter are prepared by Pechini-type polymerized

complex route followed with the calcination in the temperature range from 400∘C to 700∘C Emission spectra display characteristic5D0 rarr

7F119869(119869 = 0 1 2 3 and 4) spin forbidden f-f electronic transitions of the Eu3+ ions with the most pronounced emission

coming from 5D0 rarr7F2

transition and with the emission decays varying between 057 and 087ms for samples preparedat different temperatures Judd-Ofelt theoretical analysis of the emission spectra of Eu3+ ions was performed which allowedcalculating radiative and nonradiative emission probabilities Judd-Ofelt intensity parameters and the quantum efficiency of theEu3+ emission in the Mg

2TiO4nanoparticles The analyses showed the existence of high asymmetry around the metal ion sites

Also the largest quantum efficiency of emission of 585 is found in nanoparticles prepared at 600∘C

1 Introduction

Magnesium-orthotitanate (Mg2TiO4) is a dielectric for

microwave technology a heat resistor a capacitor for temper-ature compensation and a refractory material Strong deep-red emission can be achieved by incorporation of Mn4+ ionsin its structure [1 2] and the emission is used to improve thecolor-rendering index of phosphor-converted white-light-emitting diodes Luminescence from Mg

2TiO4can be also

realized with the incorporation of trivalent rare earth (RE)ions in its structure since the band gap of the materialis large enough (Eg sim 37 eV) to accommodate RE energylevels Then Mg

2TiO4can serve as a phosphor of different

colors depending on the RE ion used as an activator In thissense nanoparticles of Mg

2TiO4can be of particular interest

since internal light scattering in nanophosphors is negli-gible compared to bulk counterparts [3] Also nanophos-phors show stronger luminescence emission compared tobulk ones due to the modification of radiative lifetimes[4]

So far no data on the radiative and nonradiative transitionprobabilities and quantum efficiencies of emission of REimpurities in Mg

2TiO4nanoparticles have been reported

These important emission characteristics are needed to com-pare luminescence performance of the RE ions in Mg

2TiO4

with their performance in other well established hostsTherefore we aimed in this work at an analysis of the Eu3+ion emission in the Mg

2TiO4nanoparticles prepared with

Pechini-type polymerized complex route [2 5] at differentlow temperatures In addition to the experimental studiesthe Judd-Ofelt analysis of the emission spectra of Eu3+ions was performed which allowed calculating radiative andnonradiative transition probabilities Judd-Ofelt intensityparameters and the quantum efficiency of the Eu3+ emissionin theMg

2TiO4nanoparticles At low temperaturesMg

2TiO4

structure is metastable however literature results indicatethat crystallites of nanoscale dimensions may lead to a higherstability of some cubic phases [6 7] Therefore the analysisshould also provide the temperature that delivers Mg

2TiO4

nanoparticles with best luminescence properties

2 Experimental Part

21 Synthesis of Eu3+ Doped Mg2TiO4

NanoparticlesEu3+ doped Mg

2TiO4(2 at of Eu) was synthesized with

Hindawi Publishing CorporationAdvances in Condensed Matter PhysicsVolume 2015 Article ID 736517 7 pageshttpdxdoiorg1011552015736517

2 Advances in Condensed Matter Physics

MgMgTiO

x

y

z

(a)

lowast

Mg2TiO4 ICDD 01-072-6968MgTiO3 ICDD 01-075-3957

20 806040

Inte

nsity

(au

)

(0 0

3)

(1 0

1)

(0 1

2)

(1 0

4)

(0 2

4)

(3 0

0)

(1 0

10)

400∘C

450∘C

500∘C

550∘C

600∘C

650∘C

700∘C

lowastlowast lowast

lowastlowast

lowast lowastlowast

lowast

(11minus3

)

(11minus6

)

(1 1

1)

(2 2

0)

(3 1

1)

(4 0

0)

(5 1

1)

(4 4

0)

2120579 (∘)

(b)

Figure 1 Crystal structure of Eu3+ activated Mg2TiO4 (a) schematic of the unit cell (b) X-ray diffraction patterns of nanoparticles prepared

at different temperatures from 400∘C to 700∘C

Pechini-type polymerized complex route which is essentiallybased on the polyesterification between citric acid (CA) andethylene glycol (EG) [2 5] Molar ratio of precursorcomponents was magnesium oxide titanium (IV)-isopropoxide citric acid ethylene glycol = 2 1 5 20 In thefirst step titanium (IV)-isopropoxide (Alfa Aesar 97) wasdissolved in ethylene glycol (Lach-Ner 99) under constantmagnetic stirring at room temperature Then citric acid(Kemika 995) was added to the solution and stirred untilcomplete dissolution was achieved The appropriate amountofMgO and Eu

2O3were dissolved in concentrated nitric acid

at 130∘C evaporated to dryness and joined with titanium(IV)-isopropoxideEGCA mixture In the next step themixture was stirred for 1 hour at 60∘C until it becomestransparent and further stirred at 130∘C for few hoursDuring this heating process the formation of the polymerwas promoted As the colloidal solution was condensed andthe excess of solvents removed it became highly viscous andthis viscous polymeric product was decomposed at 350∘Cin 30 minutes to a dark mass precursor This mass precursorwas powdered and further calcined at 400∘C 450∘C 500∘C550∘C 600∘C 650∘C and 700∘C to obtain pure phase of Eu3+doped Mg

2TiO4nanoparticles

22 Instruments and Measurements X-ray diffraction mea-surements were performed with Rigaku SmartLab diffrac-tometer and data were recorded in a 2120579 range from 15∘ to 120∘

counting 07∘minute in 002∘ steps Transmission electronmicroscopy was performed using JEOL-JEM 2100 LaB6operated at 200 kV Photoluminescence measurements wereperformed at room temperature on Fluorolog-3 Model FL3-221 spectrofluorometer system (Horiba Jobin-Yvon) utilizing450W Xenon lamp as an excitation source for emissionmeasurements and XenonndashMercury pulsed lamp for lifetimemeasurements The emission spectra were scanned in therange of wavelengths from 430 to 790 nm The TBX-04-DPMT detector is used for both lifetime and steady state acqui-sitions The line intensities and positions of the measuredspectra were calibrated with a standard mercury-argon lamp

3 Results and Discussion

31 Microstructural Analysis Mg2TiO4crystallize in a cubic

inverse spinel structure (Fd-3m space group) [8ndash10] In thisstructureMg2+ ions are located in tetrahedral and octahedralsites while the Ti4+ ions occupy only octahedral sites asshown in Figure 1(a) Arrangement of Ti4+ and Mg2+ ions inthe octahedral sites is random

X-ray diffraction patterns of samples calcined at dif-ferent temperatures from 400∘C to 700∘C are presented inFigure 1(b)Themain diffraction peaks are indexed accordingto ICDD01-072-6968 card Pure phase of Mg

2TiO4is present

in the samples annealed in the temperature range from 400∘C

Advances in Condensed Matter Physics 3

Figure 2 TEM image of the Eu3+ activated Mg2TiO4nanoparticles

prepared at 600∘C

0

Emiss

ion

inte

nsity

(cou

nts)

Mg2TiO4 2 at Eu 400∘C4hMg2TiO4 2 at Eu 450∘C2hMg2TiO4 2 at Eu 500∘C1hMg2TiO4 2 at Eu 550∘C1hMg2TiO4 2 at Eu 600∘C1hMg2TiO4 2 at Eu 650∘C1h

5D0 rarr7F4

7F3

7F2

7F17F0

1

2

3

4

5

times 106

Wavenumbers (cmminus1)14 15 16 17

times 104

Figure 3 The emission spectra of the Eu3+ activated Mg2TiO4

nanoparticles prepared at different temperatures from 400∘C to650∘C

to 650∘C In the sample calcined at 700∘C ilmenite (MgTiO3)

phase is presented along with Mg2TiO4

TEM image in Figure 2 shows morphology of particlesof Mg

2TiO4doped Eu3+ sample annealed at 600∘C for

1 hour The sample is composed of loosely agglomeratednanoparticles of 5 to 10 nm in diameter

32 Photoluminescence Emission Spectra and Lifetime Mea-surements The emission spectra of Mg

2TiO4samples doped

with 2 at Eu and annealed in the 400ndash650∘C temperaturerange are presented in Figure 3 Due to even number ofelectrons in the 4f shell (4f6 configuration) the crystal-fieldperturbation by the host matrix lifts partly or completelythe degeneracies of the Eu3+ levels [11] Therefore emissionspectra show five characteristic bands centered around 17271

Table 1 Lifetimes of the 5D0 emission level of Eu3+ in Mg2TiO4nanoparticles prepared at different temperatures

Mg2TiO4 doped 2 at Eu3+

Annealing temperature (∘C) Lifetime (120583s)400 573450 741500 818550 853600 872650 851

16892 16287 15290 and 14245 cmminus1 that originate from5D0 rarr

7F119869(119869 = 0 1 2 3 and 4) spin forbidden f-f electronic

transitions of the Eu3+ ions The 5D0

rarr7F1transition is

magnetic dipole in nature and follows the selection rule Δ119869 =

1 Its intensity is independent of the hostmatrix On the otherhand the 5D0 rarr

7F246 are ldquothe forcedrdquo (induced) electricdipole transitions known to be forbidden by the Laporteselection rule and may occur due to the mixing of the 4forbitals with opposite parity at the low symmetry sites The5D0 rarr

7F2 is known as a hypersensitive transition becauseit is easily affected by the local environment around europiumion and its intensity depends on the symmetry of crystalfield around the europium ion The intensity of 5D0 rarr

7F2transition is themost intense across the emission spectraThe5D0 rarr

7F0 transition is not allowed since 0ndash0 transitionsare forbidden by the selection rule 119869 = 0 rarr 119869

1015840= 0 The

appearance of this transition is mainly due to the 119869-mixingeffect [12] and indicates that Eu3+ ion is located in a sitewithout an inversion center Low energy transitions 5D0 rarr

7F3 and5D0 rarr

7F4 are also clearly visible Emissions from5D0 rarr

7F5 (12990ndash13510 cmminus1) and 5D0 rarr7F6 (11900ndash

12350 cmminus1) transitions could not be detected due to theinstrument limitations

From emission spectra (Figure 3) one can notice that theemission intensity increases with the increase of annealingtemperature and that there is no significant change in theemission spectrarsquos shape The emission decays of the 5D

0

emitting level are obtained under 394 nm excitation Averagelifetime values are calculated using the following equation

120591avg =

int

infin

0 119905119868 (119905) 119889119905

int

infin

0 119868 (119905) 119889119905

(1)

where 119868(119905) represents the luminescence intensity (correctedfor the background) at time 119905 The results are presented inTable 1

In all samples the highest emission intensity is observedfor 5D0 rarr

7F2 transition The intensity of this transitionFigure 2 and the lifetime values Table 1 enlarge with therise of the annealing temperature up to 650∘C These valueshowever decrease in the sample prepared at 650∘C

33 Judd-Ofelt Calculations and Results The Judd-Ofelt the-ory [13 14] describes intensities of transitions of lanthanides


and actinides in solids and solutions whereas Judd-Ofeltparameters characterize local structure and bonding in thevicinity of rare earth ions This theory provides informationabout oscillator strengths radiative lifetime and emissionprobabilities The analysis also provides values of quantumefficiency

According to J-O theory [13 14] theoretical expression forthe oscillator strength of an induced electric dipole transitionfrom the ground state to an excited state is

119891

=

81205872119898119888]

3ℎ (2119869 + 1)(119899

2+ 2)

2

9119899sum

120582=246Ω120582

10038161003816100381610038161003816⟨Ψ119869

10038171003817100381710038171003817119880

(120582)10038171003817100381710038171003817Ψ119869

1015840⟩

10038161003816100381610038161003816

2

(2)

where ℎ denotes Planck constant (6626 times 10minus34 Jsdots 4135 times

10minus15 eVsdots) 2119869 + 1 is the degeneracy of the initial state 119899 isthe refractive index Ω

120582are the Judd-Ofelt parameters and

⟨Ψ119869119880(120582)

Ψ1198691015840⟩ terms are the double reducedmatrix elements

of unit tensor operators whose values are independent ofthe local environment of the ion According to the Judd-Ofelt theory radiative transition probability 119860 is related toits dipole strength according to the following equation

119860(Ψ

1015840119869

1015840 Ψ

1015840119869

1015840)

=

6512058741198902

3ℎ (21198691015840 + 1) 1205823 [119899(

1198992+ 22

)

2

119863ED + 119899

2119863MD]

(3)

where 119863ED and 119863MD represent the electric and magneticdipole strengths respectively Transition probabilities of therare earths are composed mainly of the electric dipolecontribution 5D

0rarr7F119869(119869= 2 4) and to amuch lesser extent

by themagnetic-dipole contribution 5D0

rarr7F1The 5D

0rarr

7F3transition is forbidden according to Judd-Ofelt theory

both inmagnetic and induced electric dipole scheme and thistransition can only gain intensity via 119869-mixing [15 16] Alsothe 5D

0rarr7F0transition is strictly forbidden according

to the standard Judd-Ofelt theory Therefore these twotransitions will not be considered in determining transitionprobabilities The intensity of 5D

0rarr7F1magnetic dipole

transition is largely independent of the environment and canbe considered in a first approximation to be constant [17]The magnetic dipole transition can be calculated by theory[15 18]

119863MD = 96times 10minus42 esu2 cm2= 096times 10minus54 J sdotm3

= 599times 10minus36 eV sdotm3(4)

The strength of all induced electric dipole transitions is

119863ED (119869 119869

1015840) = 119890

2sum

120582=246Ω120582

10038161003816100381610038161003816⟨Ψ119869

10038171003817100381710038171003817119880

(120582)10038171003817100381710038171003817Ψ119869

1015840⟩

10038161003816100381610038161003816

2 (5)

where squared reduced matrix elements |⟨Ψ119869119880(120582)

Ψ1198691015840⟩|2

have values independent of the host matrix For the caseof Eu3+ these values are tabulated in [18ndash20] and Judd-Ofelt intensity parameters can be evaluated solely from

the emission spectrum because nondiagonal elements of the|⟨Ψ119869119880

(120582)Ψ1198691015840⟩|2 matrix have zero values according to the

following equation

Ω120582

=

119863MD]31

1198902]3120582

91198993

119899 (1198992+ 2)2 100381610038161003816

1003816⟨Ψ119869

1003817100381710038171003817119880(120582)10038171003817

10038171003817Ψ10158401198691015840⟩

1003816100381610038161003816

2int 119868120582(]120582)

int 1198681 (]1)

(6)

For the calculations the value of refractive index of 1691 forMg2TiO4is taken from the literature [21] According to [22]

radiative emission probability of magnetic dipole transition119860 (5D

0rarr7F1) has value of 5734 sminus1 for the 50(NaPO

3)6+

10TeO2+ 20AlF

3+ 19LiF + 1Eu

2O3glass with a refractive

index of 1591 Taking this value as a reference and with thewell-known correction factor of (1198991591)3 which can bederived from the general equations for the magnetic dipoletransition probability rates [23 24] 119860 (5D

0rarr7F1) =

6885 sminus1 is calculated for the radiative emission probability ofmagnetic dipole transition of Eu3+ in Mg

2TiO4 The intensity

of this transition can be considered as a reference for alltransitions originating from the 5D

0excited state [11] Then

it is possible to calculate radiative emission probabilities ofall transitions originating from the 5D

0excited state from

the ratios of areas 119878 under corresponding emission bands inFigure 3 [20 22]

119860(

5D0 997888rarr7F24)

= 119860 (

5D0 997888rarr7F1)

119878 (5D0 997888rarr

7F24)119878 (

5D0 997888rarr7F1)

(7)

Total radiative emission probability 119860119877 defined as the sum

of all radiative emission probabilities

119860119877= sum

120582=124119860120582 (8)

can be further used to calculate nonradiative probability119860NR (which includes relaxation by multiphonon emissionand effective energy transfer rates arising from ion-ioninteractions [11]) and emission quantum efficiency 120578 (theratio between the number of photons emitted by the Eu3+ ionto the number of those absorbed)

119860NR =

1120591

minus119860NR

120578 =

119860119877

119860119877+ 119860NR

(9)

The Ω2intensity parameter describes hypersensitivity of

5D0

rarr7F2transition since it is affected by the symmetry

of local surrounding around the Eu3+ site Ω4and Ω

6

parameters are associated with the viscosity and rigidity ofthe host material Several reports [25ndash28] used Ω

2to assess

the magnitude of covalence between Eu3+ and surroundingligands (the larger the Ω

2 the stronger the covalence)

however one should note that there are number of competing


Table 2 Intensity parameters radiative and nonradiative emission probabilities quantum efficiencies and asymmetry ratios of Eu3+ emissionfromMg2TiO4 nanoparticles prepared at different temperatures from 400∘C to 650∘C

119879 (∘C) Ω2(10minus20 cmminus2) Ω

4(10minus20 cmminus2) 119860 (sminus1) 119860NR (s

minus1) 120578 () 119877

400 523 294 30968 143551 1775 322450 880 450 48737 86215 3611 546500 1071 508 57753 64496 4724 665550 1142 530 60979 56253 5201 710600 1246 623 67120 47558 5853 775650 1224 588 65454 52054 5570 760

400 650600550500450Temperature (∘C)

Ω2 (cmminus2)Ω4 (cmminus2)

Ω(c

mminus2)

14 times 10minus19

12 times 10minus19

10 times 10minus19

80 times 10minus20

60 times 10minus20

40 times 10minus20

20 times 10minus20

(a)

3

4

5

6

7

8

9

Asy

mm

etric

ratio

400 650600550500450Temperature (∘C)

Mg2TiO4 2 at Eu

(b)

Figure 4 (a)Ω2(black squares) andΩ

4(red circles) intensity parameters and (b) asymmetric ratio of Eu3+ emission inMg

2TiO4nanoparticles

prepared at different temperatures

mechanisms for induced electric dipole transitions so thedominant mechanism could not be determined from thesingle parameter Luminescence intensity ratio 119877 = (

5D0

rarr

7F2)(5D0

rarr7F1) is also known as asymmetry ratio [29]

Higher values of 119877 indicate lower symmetry around thetrivalent europium ions [30 31] Ω

2and 119877 reveal similar

physical information on the bonding nature between Eu3+ion and the surrounding anions and explain the short rangeeffects in local structure around Eu3+ ions [28] Ω

6intensity

parameter could not be determined because 5D0

rarr7F6

emission in this sample could not be detected due to theinstrumental limitations

Calculated Judd-Ofelt parameters show variation withthe annealing temperature and their values are presented inTable 2 along with the values of radiative and nonradiativeemission probabilities quantum efficiencies and asymmetryratios

Ω2and Ω

4dependence on temperature is displayed in

Figure 4(a) and asymmetric ratio is presented in Figure 4(b)One can notice that the values ofΩ

2andΩ

4increase with the

increase of annealing temperature until 600∘C Eu3+ emissionfrom the sample prepared at 650∘Chas lower values ofΩ

2and

Ω4than in the case of sample prepared at 600∘C This result

indicates that local environment of the Eu3+ ion changes attemperatures higher than 600∘C In the complete tempera-ture rangeΩ

2is larger thanΩ

4The relatively high value ofΩ

2

and the observed trend indicate a relatively high asymmetryat the Eu3+ siteThese results are in agreement with the valuesof luminescence intensity ratio 323 546 665 710 775and 760 One should notice the trend of 119877 value increasewith the annealing temperature up to 600∘C and decrease for650∘C A high value of this ratio indicates low symmetry ofthe crystal field around the europium ion due to distortionof the surrounding bonds [32] The start of reverse trendof change of Judd-Ofelt parameters and asymmetric ratioat temperature of 650∘C indicates the beginning of materialstructural disorder since at that temperature the decrease ofquantum efficiency is also observed

Figure 5(a) shows changes of radiative and nonradiativeemission probabilities of Eu3+ emissions in samples preparedat different temperatures Until 600∘C radiative emissionprobability increases and nonradiative decreases Thetrend reverses for sample prepared at 650∘C The quantumefficiency of emission Figure 5(b) increases from 1775 insample annealed at 400∘C to 5853 for a sample prepared at600∘C The quantum efficiency of Eu3+ emission in sample


200

400

600

800

1000

1200

1400

1600

Radiative Nonradiative

400 650600550500450Temperature (∘C)

Tran

sitio

n ra

te (s

minus1)

(a)

10

20

30

40

50

60

70

Qua

ntum

effici

ency

()

400 650600550500450Temperature (∘C)

Mg2TiO4 2 at Eu

(b)

Figure 5 (a) Radiative (black squares) and nonradiative transition rates (red circles) and (b) quantum efficiency of Eu3+ emission inMg2TiO4

nanoparticles prepared at different temperatures

prepared at 650∘C is 5570 lower than for sample preparedat 600∘C

One should note that the values of quantum efficiency areslightly underestimated since calculation does not account5D0

rarr7F356

emissions However the trend of quantumefficiency changewith annealing temperature is unaffected bythis deficiency Also refraction index is wavelength depen-dent physical property so taking the constant value intocalculation introduces error into results however the erroris small since the refractive index changes are small overthe wavelength region of interest [20] These simplificationsare justified for the sake of comparison of JO parametersand emission parameters between samples since small errorscannot change observed trends It is acknowledged that Judd-Ofelt theory estimates transition probabilities with accuracygenerally not worse than 10 [33]

4 Conclusion

To conclude Eu3+ doped Mg2TiO4nanoparticles of about 5

to 10 nm in size can be prepared with Pechini-type polymer-ized complex route after annealing in the low-temperaturerange from400∘C to 650∘CThebest luminescence propertiesshowed nanoparticles prepared at 600∘C exhibiting quantumefficiency of emission of 585 and emission lifetime of872120583s In all samples Judd-Ofelt intensity parameter Ω

2

was larger than Ω4 and relatively high values of Ω

2and

asymmetry ratio are observed The latter indicate relativelyhigh asymmetry at the Eu3+ sites

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors acknowledge the financial support of the Min-istry of Education and Science of the Republic of Serbia(Project no 45020) and the support from the APV ProvincialSecretariat for Science and Technological Development of theRepublic of Serbia through Project no 114-451-18502014-03

References

[1] T Ye S Li X Wu et al ldquoSol-gel preparation of efficientred phosphor Mg

2TiO4Mn4+ and XAFS investigation on the

substitution of Mn4+ for Ti4+rdquo Journal of Materials ChemistryC vol 1 no 28 pp 4327ndash4333 2013

[2] M M Medic M G Brik G Drazic Z M Antic V MLojpur andMDDramicanin ldquoDeep-red emittingMn4+ dopedMg2TiO4nanoparticlesrdquo Journal of Physical Chemistry C vol

119 no 1 pp 724ndash730 2014[3] G Liu and X Chen ldquoSpectroscopic properties of lanthanides

in nanomaterialsrdquo inHandbook on the Physics and Chemistry ofRare Earths J-C B Karl A Gschneidner and K P Vitalij Edspp 99ndash169 Elsevier 2007

[4] R S Meltzer S P Feofilov B Tissue and H B Yuan ldquoDepen-dence of fluorescence lifetimes of Y

2O3Eu3+ nanoparticles on

the surrounding mediumrdquo Physical Review B vol 60 no 20pp R14012ndashR14015 1999

[5] S Culubrk Z Antic M Marinovic-Cincovic P S Ahrenkieland M D Dramicanin ldquoSynthesis and luminescent propertiesof rare earth (Sm3+ and Eu3+) Doped Gd

2Ti2O7pyrochlore

nanopowdersrdquo Optical Materials vol 37 pp 598ndash606 2014[6] C Huang Z Tang Z Zhang and J Gong ldquoStudy on a new

environmentally benign method and its feasibility of preparingnanometer zirconia powderrdquo Materials Research Bulletin vol35 no 9 pp 1503ndash1508 2000


[7] P R Arya P Jha andAKGanguli ldquoSynthesis characterizationand dielectric properties of nanometer-sized barium strontiumtitanates prepared by the polymeric citrate precursor methodrdquoJournal of Materials Chemistry vol 13 no 2 pp 415ndash423 2003

[8] F W Barth Tom and E Posnjak ldquoSpinel structures with andwithout variate atom equipointsrdquo Zeitschrift fur Kristallogra-phiemdashCrystalline Materials vol 82 no 1 article 325 1932

[9] H S C OrsquoNeill S A T Redfern S Kesson and S ShortldquoAn in situ neutron diffraction study of cation disordering insynthetic qandilite Mg

2TiO4at high temperaturesrdquo American

Mineralogist vol 88 no 5 pp 860ndash865 2003[10] R L Millard R C Peterson and B K Hunter ldquoStudy of the

cubic to tetragonal transition in Mg2TiO4and Zn

2TiO4spinels

by 17O MAS NMR and rietveld refinement of X-ray diffractiondatardquo American Mineralogist vol 80 no 9-10 pp 885ndash8961995

[11] K Binnemans ldquoInterpretation of europium(III) spectrardquo Coor-dination Chemistry Reviews vol 295 pp 1ndash45 2015

[12] P A Tanner Y Y Yeung and L Ning ldquoWhat factors affect the5D0energy of Eu3+ An investigation of nephelauxetic effectsrdquo

The Journal of Physical Chemistry A vol 117 no 13 pp 2771ndash2781 2013

[13] B R Judd ldquoOptical absorption intensities of rare-earth ionsrdquoPhysical Review vol 127 no 3 pp 750ndash761 1962

[14] G S Ofelt ldquoIntensities of crystal spectra of rareminusearth ionsrdquoTheJournal of Chemical Physics vol 37 no 3 pp 511ndash520 1962

[15] M J Weber T E Varitimos and B H Matsinger ldquoOpticalintensities of rare-earth ions in yttrium orthoaluminaterdquo Physi-cal Review B vol 8 no 1 pp 47ndash53 1973

[16] J E Lowther ldquoSpectroscopic transition probabilities of rareearth ionsrdquo Journal of Physics C Solid State Physics vol 7 no23 pp 4393ndash4402 1974

[17] C Gorller-Walrand L Fluyt A Ceulemans and W T Car-nall ldquoMagnetic dipole transitions as standards for Judd-Ofeltparametrization in lanthanide spectrardquoThe Journal of ChemicalPhysics vol 95 no 5 pp 3099ndash3106 1991

[18] M H V Werts R T F Jukes and J W Verhoeven ldquoThe emis-sion spectrum and the radiative lifetime of Eu3+ in luminescentlanthanide complexesrdquo Physical Chemistry Chemical Physicsvol 4 no 9 pp 1542ndash1548 2002

[19] W T Carnall P R Fields and K Rajnak ldquoSpectral intensitiesof the trivalent lanthanides and actinides in solution II Pm3+Sm3+ Eu3+ Gd3+ Tb3+ Dy3+ and Ho3+rdquoThe Journal of Chem-ical Physics vol 49 no 10 pp 4412ndash4423 1968

[20] L Dacanin S R Lukic D M Petrovic M Nikolic and MD Dramicanin ldquoJudd-Ofelt analysis of luminescence emis-sion from Zn

2SiO4Eu3+ nanoparticles obtained by a polymer-

assisted solgel methodrdquo Physica B Condensed Matter vol 406no 11 pp 2319ndash2322 2011

[21] M J Weber Handbook of Optical Materials CRC Press BocaRaton Fla USA 2003

[22] D Uma Maheswari J Suresh Kumar L R Moorthy K JangandM Jayasimhadri ldquoEmission properties of Eu3+ ions in alkalitellurofluorophosphate glassesrdquo Physica B Condensed Mattervol 403 no 10-11 pp 1690ndash1694 2008

[23] J C Boyer F Vetrone J A Capobianco A Speghini and MBettinelli ldquoVariation of fluorescence lifetimes and judd-ofeltparameters between Eu3+doped bulk and nanocrystalline cubicLu2O3rdquo Journal of Physical Chemistry B vol 108 no 52 pp

20137ndash20143 2004

[24] C Liu J Liu and K Dou ldquoJudd-Ofelt intensity parametersand spectral properties of Gd

2O3Eu3+ nanocrystalsrdquo Journal of

Physical Chemistry B vol 110 no 41 pp 20277ndash20281 2006[25] C Koeppen S Yamada G Jiang A F Garito and L R Dalton

ldquoRare-earth organic complexes for amplification in polymeroptical fibers and waveguidesrdquo Journal of the Optical Society ofAmerica B Optical Physics vol 14 no 1 pp 155ndash162 1997

[26] S S Braga R A Sa Ferreira I S Goncalves et al ldquoSynthesischaracterization and luminescence of 120573-cyclodextrin inclu-sion compounds containing europium(III) and gadolinium(III)tris(120573-diketonates)rdquo The Journal of Physical Chemistry B vol106 no 44 pp 11430ndash11437 2002

[27] G Ehrhart M Bouazaoui B Capoen et al ldquoEffects of rare-earth concentration and heat-treatment on the structural andluminescence properties of europium-doped zirconia sol-gelplanar waveguidesrdquo Optical Materials vol 29 no 12 pp 1723ndash1730 2007

[28] P Babu andC K Jayasankar ldquoOptical spectroscopy of Eu3+ ionsin lithium borate and lithium fluoroborate glassesrdquo Physica BCondensed Matter vol 279 no 4 pp 262ndash281 2000

[29] A Patra E Sominska S Ramesh et al ldquoSonochemical prepa-ration and characterization of Eu

2O3and Tb

2O3doped in and

coated on silica and alumina nanoparticlesrdquo The Journal ofPhysical Chemistry B vol 103 no 17 pp 3361ndash3365 1999

[30] K Binnemans K Van Herck and C Gorller-Walrand ldquoInflu-ence of dipicolinate ligands on the spectroscopic properties ofeuropium(III) in solutionrdquo Chemical Physics Letters vol 266no 3-4 pp 297ndash302 1997

[31] M Kumar T K Seshagiri and S V Godbole ldquoFluorescencelifetime and JuddndashOfelt parameters of Eu3+ doped SrBPO

5rdquo

Physica B Condensed Matter vol 410 no 1 pp 141ndash146 2013[32] V ETHorđevic Z Antic M G Nikolic and M D Dramicanin

ldquoComparative structural and photoluminescent study of Eu3+-doped La

2O3and La(OH)

3nanocrystalline powdersrdquo Journal of

Physics and Chemistry of Solids vol 75 no 2 pp 276ndash282 2014[33] R Rolli K GattererMWachtierM Bettinelli A Speghini and

D Ajo ldquoOptical spectroscopy of lanthanide ions in ZnO-TeO2

glassesrdquo Spectrochimica Acta Part A Molecular and Biomolecu-lar Spectroscopy vol 57 no 10 pp 2009ndash2017 2001

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

High Energy PhysicsAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


FluidsJournal of

Atomic and Molecular Physics

Journal of



Advances in Condensed Matter Physics

OpticsInternational Journal of



AstronomyAdvances in

International Journal of


Superconductivity


Statistical MechanicsInternational Journal of


GravityJournal of


AstrophysicsJournal of


Physics Research International


Solid State PhysicsJournal of

Computational Methods in Physics

Journal of



Soft MatterJournal of

Hindawi Publishing Corporationhttpwwwhindawicom

AerodynamicsJournal of

Volume 2014


PhotonicsJournal of


Journal of

Biophysics


ThermodynamicsJournal of


MgMgTiO

x

y

z

(a)

lowast

Mg2TiO4 ICDD 01-072-6968MgTiO3 ICDD 01-075-3957

20 806040

Inte

nsity

(au

)

(0 0

3)

(1 0

1)

(0 1

2)

(1 0

4)

(0 2

4)

(3 0

0)

(1 0

10)

400∘C

450∘C

500∘C

550∘C

600∘C

650∘C

700∘C

lowastlowast lowast

lowastlowast

lowast lowastlowast

lowast

(11minus3

)

(11minus6

)

(1 1

1)

(2 2

0)

(3 1

1)

(4 0

0)

(5 1

1)

(4 4

0)

2120579 (∘)

(b)

Figure 1 Crystal structure of Eu3+ activated Mg2TiO4 (a) schematic of the unit cell (b) X-ray diffraction patterns of nanoparticles prepared

at different temperatures from 400∘C to 700∘C

Pechini-type polymerized complex route which is essentiallybased on the polyesterification between citric acid (CA) andethylene glycol (EG) [2 5] Molar ratio of precursorcomponents was magnesium oxide titanium (IV)-isopropoxide citric acid ethylene glycol = 2 1 5 20 In thefirst step titanium (IV)-isopropoxide (Alfa Aesar 97) wasdissolved in ethylene glycol (Lach-Ner 99) under constantmagnetic stirring at room temperature Then citric acid(Kemika 995) was added to the solution and stirred untilcomplete dissolution was achieved The appropriate amountofMgO and Eu

2O3were dissolved in concentrated nitric acid

at 130∘C evaporated to dryness and joined with titanium(IV)-isopropoxideEGCA mixture In the next step themixture was stirred for 1 hour at 60∘C until it becomestransparent and further stirred at 130∘C for few hoursDuring this heating process the formation of the polymerwas promoted As the colloidal solution was condensed andthe excess of solvents removed it became highly viscous andthis viscous polymeric product was decomposed at 350∘Cin 30 minutes to a dark mass precursor This mass precursorwas powdered and further calcined at 400∘C 450∘C 500∘C550∘C 600∘C 650∘C and 700∘C to obtain pure phase of Eu3+doped Mg

2TiO4nanoparticles

22 Instruments and Measurements X-ray diffraction mea-surements were performed with Rigaku SmartLab diffrac-tometer and data were recorded in a 2120579 range from 15∘ to 120∘

counting 07∘minute in 002∘ steps Transmission electronmicroscopy was performed using JEOL-JEM 2100 LaB6operated at 200 kV Photoluminescence measurements wereperformed at room temperature on Fluorolog-3 Model FL3-221 spectrofluorometer system (Horiba Jobin-Yvon) utilizing450W Xenon lamp as an excitation source for emissionmeasurements and XenonndashMercury pulsed lamp for lifetimemeasurements The emission spectra were scanned in therange of wavelengths from 430 to 790 nm The TBX-04-DPMT detector is used for both lifetime and steady state acqui-sitions The line intensities and positions of the measuredspectra were calibrated with a standard mercury-argon lamp

3 Results and Discussion

31 Microstructural Analysis Mg2TiO4crystallize in a cubic

inverse spinel structure (Fd-3m space group) [8ndash10] In thisstructureMg2+ ions are located in tetrahedral and octahedralsites while the Ti4+ ions occupy only octahedral sites asshown in Figure 1(a) Arrangement of Ti4+ and Mg2+ ions inthe octahedral sites is random

X-ray diffraction patterns of samples calcined at dif-ferent temperatures from 400∘C to 700∘C are presented inFigure 1(b)Themain diffraction peaks are indexed accordingto ICDD01-072-6968 card Pure phase of Mg

2TiO4is present

in the samples annealed in the temperature range from 400∘C



prepared at 600∘C

0

Emiss

ion

inte

nsity

(cou

nts)


5D0 rarr7F4

7F3

7F2

7F17F0

1

2

3

4

5

times 106


times 104









2TiO4samples doped















1015840= 0 The


7F3 and5D0 rarr





0


120591avg =

int

infin

0 119905119868 (119905) 119889119905

int

infin

0 119868 (119905) 119889119905

(1)








119891

=

81205872119898119888]

3ℎ (2119869 + 1)(119899

2+ 2)

2

9119899sum

120582=246Ω120582

10038161003816100381610038161003816⟨Ψ119869

10038171003817100381710038171003817119880

(120582)10038171003817100381710038171003817Ψ119869

1015840⟩

10038161003816100381610038161003816

2

(2)




⟨Ψ119869119880(120582)



119860(Ψ

1015840119869

1015840 Ψ

1015840119869

1015840)

=

6512058741198902

3ℎ (21198691015840 + 1) 1205823 [119899(

1198992+ 22

)

2

119863ED + 119899

2119863MD]

(3)




rarr7F1The 5D

0rarr










119863ED (119869 119869

1015840) = 119890

2sum

120582=246Ω120582

10038161003816100381610038161003816⟨Ψ119869

10038171003817100381710038171003817119880

(120582)10038171003817100381710038171003817Ψ119869

1015840⟩

10038161003816100381610038161003816

2 (5)


Ψ1198691015840⟩|2




following equation

Ω120582

=

119863MD]31

1198902]3120582

91198993

119899 (1198992+ 2)2 100381610038161003816

1003816⟨Ψ119869

1003817100381710038171003817119880(120582)10038171003817

10038171003817Ψ10158401198691015840⟩

1003816100381610038161003816

2int 119868120582(]120582)

int 1198681 (]1)

(6)




3)6+

10TeO2+ 20AlF

3+ 19LiF + 1Eu



0rarr7F1) =


2TiO4 The intensity




0excited state from


119860(

5D0 997888rarr7F24)

= 119860 (

5D0 997888rarr7F1)

119878 (5D0 997888rarr

7F24)119878 (

5D0 997888rarr7F1)

(7)



119860119877= sum

120582=124119860120582 (8)


119860NR =

1120591

minus119860NR

120578 =

119860119877

119860119877+ 119860NR

(9)


5D0



6


2to assess








minus1) 120578 () 119877

400 523 294 30968 143551 1775 322450 880 450 48737 86215 3611 546500 1071 508 57753 64496 4724 665550 1142 530 60979 56253 5201 710600 1246 623 67120 47558 5853 775650 1224 588 65454 52054 5570 760

400 650600550500450Temperature (∘C)


Ω(c

mminus2)

14 times 10minus19

12 times 10minus19

10 times 10minus19

80 times 10minus20

60 times 10minus20

40 times 10minus20

20 times 10minus20

(a)

3

4

5

6

7

8

9

Asy

mm

etric

ratio

400 650600550500450Temperature (∘C)

Mg2TiO4 2 at Eu

(b)



2TiO4nanoparticles



5D0

rarr

7F2)(5D0





6intensity


rarr7F6



Ω2and Ω



2andΩ

4increase with the


2and



2is larger thanΩ


2




200

400

600

800

1000

1200

1400

1600


400 650600550500450Temperature (∘C)

Tran

sitio

n ra

te (s

minus1)

(a)

10

20

30

40

50

60

70

Qua

ntum

effici

ency

()

400 650600550500450Temperature (∘C)

Mg2TiO4 2 at Eu

(b)





rarr7F356


4 Conclusion



2


2and




Acknowledgments


References











2Ti2O7pyrochlore










2TiO4spinels


















20137ndash20143 2004









2O3and Tb

2O3doped in and




5rdquo



2O3and La(OH)










FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics





prepared at 600∘C

0

Emiss

ion

inte

nsity

(cou

nts)


5D0 rarr7F4

7F3

7F2

7F17F0

1

2

3

4

5

times 106


times 104









2TiO4samples doped















1015840= 0 The


7F3 and5D0 rarr





0


120591avg =

int

infin

0 119905119868 (119905) 119889119905

int

infin

0 119868 (119905) 119889119905

(1)








119891

=

81205872119898119888]

3ℎ (2119869 + 1)(119899

2+ 2)

2

9119899sum

120582=246Ω120582

10038161003816100381610038161003816⟨Ψ119869

10038171003817100381710038171003817119880

(120582)10038171003817100381710038171003817Ψ119869

1015840⟩

10038161003816100381610038161003816

2

(2)




⟨Ψ119869119880(120582)



119860(Ψ

1015840119869

1015840 Ψ

1015840119869

1015840)

=

6512058741198902

3ℎ (21198691015840 + 1) 1205823 [119899(

1198992+ 22

)

2

119863ED + 119899

2119863MD]

(3)




rarr7F1The 5D

0rarr










119863ED (119869 119869

1015840) = 119890

2sum

120582=246Ω120582

10038161003816100381610038161003816⟨Ψ119869

10038171003817100381710038171003817119880

(120582)10038171003817100381710038171003817Ψ119869

1015840⟩

10038161003816100381610038161003816

2 (5)


Ψ1198691015840⟩|2




following equation

Ω120582

=

119863MD]31

1198902]3120582

91198993

119899 (1198992+ 2)2 100381610038161003816

1003816⟨Ψ119869

1003817100381710038171003817119880(120582)10038171003817

10038171003817Ψ10158401198691015840⟩

1003816100381610038161003816

2int 119868120582(]120582)

int 1198681 (]1)

(6)




3)6+

10TeO2+ 20AlF

3+ 19LiF + 1Eu



0rarr7F1) =


2TiO4 The intensity




0excited state from


119860(

5D0 997888rarr7F24)

= 119860 (

5D0 997888rarr7F1)

119878 (5D0 997888rarr

7F24)119878 (

5D0 997888rarr7F1)

(7)



119860119877= sum

120582=124119860120582 (8)


119860NR =

1120591

minus119860NR

120578 =

119860119877

119860119877+ 119860NR

(9)


5D0



6


2to assess








minus1) 120578 () 119877

400 523 294 30968 143551 1775 322450 880 450 48737 86215 3611 546500 1071 508 57753 64496 4724 665550 1142 530 60979 56253 5201 710600 1246 623 67120 47558 5853 775650 1224 588 65454 52054 5570 760

400 650600550500450Temperature (∘C)


Ω(c

mminus2)

14 times 10minus19

12 times 10minus19

10 times 10minus19

80 times 10minus20

60 times 10minus20

40 times 10minus20

20 times 10minus20

(a)

3

4

5

6

7

8

9

Asy

mm

etric

ratio

400 650600550500450Temperature (∘C)

Mg2TiO4 2 at Eu

(b)



2TiO4nanoparticles



5D0

rarr

7F2)(5D0





6intensity


rarr7F6



Ω2and Ω



2andΩ

4increase with the


2and



2is larger thanΩ


2




200

400

600

800

1000

1200

1400

1600


400 650600550500450Temperature (∘C)

Tran

sitio

n ra

te (s

minus1)

(a)

10

20

30

40

50

60

70

Qua

ntum

effici

ency

()

400 650600550500450Temperature (∘C)

Mg2TiO4 2 at Eu

(b)





rarr7F356


4 Conclusion



2


2and




Acknowledgments


References











2Ti2O7pyrochlore










2TiO4spinels


















20137ndash20143 2004









2O3and Tb

2O3doped in and




5rdquo



2O3and La(OH)










FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics






119891

=

81205872119898119888]

3ℎ (2119869 + 1)(119899

2+ 2)

2

9119899sum

120582=246Ω120582

10038161003816100381610038161003816⟨Ψ119869

10038171003817100381710038171003817119880

(120582)10038171003817100381710038171003817Ψ119869

1015840⟩

10038161003816100381610038161003816

2

(2)




⟨Ψ119869119880(120582)



119860(Ψ

1015840119869

1015840 Ψ

1015840119869

1015840)

=

6512058741198902

3ℎ (21198691015840 + 1) 1205823 [119899(

1198992+ 22

)

2

119863ED + 119899

2119863MD]

(3)




rarr7F1The 5D

0rarr










119863ED (119869 119869

1015840) = 119890

2sum

120582=246Ω120582

10038161003816100381610038161003816⟨Ψ119869

10038171003817100381710038171003817119880

(120582)10038171003817100381710038171003817Ψ119869

1015840⟩

10038161003816100381610038161003816

2 (5)


Ψ1198691015840⟩|2




following equation

Ω120582

=

119863MD]31

1198902]3120582

91198993

119899 (1198992+ 2)2 100381610038161003816

1003816⟨Ψ119869

1003817100381710038171003817119880(120582)10038171003817

10038171003817Ψ10158401198691015840⟩

1003816100381610038161003816

2int 119868120582(]120582)

int 1198681 (]1)

(6)




3)6+

10TeO2+ 20AlF

3+ 19LiF + 1Eu



0rarr7F1) =


2TiO4 The intensity




0excited state from


119860(

5D0 997888rarr7F24)

= 119860 (

5D0 997888rarr7F1)

119878 (5D0 997888rarr

7F24)119878 (

5D0 997888rarr7F1)

(7)



119860119877= sum

120582=124119860120582 (8)


119860NR =

1120591

minus119860NR

120578 =

119860119877

119860119877+ 119860NR

(9)


5D0



6


2to assess








minus1) 120578 () 119877

400 523 294 30968 143551 1775 322450 880 450 48737 86215 3611 546500 1071 508 57753 64496 4724 665550 1142 530 60979 56253 5201 710600 1246 623 67120 47558 5853 775650 1224 588 65454 52054 5570 760

400 650600550500450Temperature (∘C)


Ω(c

mminus2)

14 times 10minus19

12 times 10minus19

10 times 10minus19

80 times 10minus20

60 times 10minus20

40 times 10minus20

20 times 10minus20

(a)

3

4

5

6

7

8

9

Asy

mm

etric

ratio

400 650600550500450Temperature (∘C)

Mg2TiO4 2 at Eu

(b)



2TiO4nanoparticles



5D0

rarr

7F2)(5D0





6intensity


rarr7F6



Ω2and Ω



2andΩ

4increase with the


2and



2is larger thanΩ


2




200

400

600

800

1000

1200

1400

1600


400 650600550500450Temperature (∘C)

Tran

sitio

n ra

te (s

minus1)

(a)

10

20

30

40

50

60

70

Qua

ntum

effici

ency

()

400 650600550500450Temperature (∘C)

Mg2TiO4 2 at Eu

(b)





rarr7F356


4 Conclusion



2


2and




Acknowledgments


References











2Ti2O7pyrochlore










2TiO4spinels


















20137ndash20143 2004









2O3and Tb

2O3doped in and




5rdquo



2O3and La(OH)










FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics







minus1) 120578 () 119877

400 523 294 30968 143551 1775 322450 880 450 48737 86215 3611 546500 1071 508 57753 64496 4724 665550 1142 530 60979 56253 5201 710600 1246 623 67120 47558 5853 775650 1224 588 65454 52054 5570 760

400 650600550500450Temperature (∘C)


Ω(c

mminus2)

14 times 10minus19

12 times 10minus19

10 times 10minus19

80 times 10minus20

60 times 10minus20

40 times 10minus20

20 times 10minus20

(a)

3

4

5

6

7

8

9

Asy

mm

etric

ratio

400 650600550500450Temperature (∘C)

Mg2TiO4 2 at Eu

(b)



2TiO4nanoparticles



5D0

rarr

7F2)(5D0





6intensity


rarr7F6



Ω2and Ω



2andΩ

4increase with the


2and



2is larger thanΩ


2




200

400

600

800

1000

1200

1400

1600


400 650600550500450Temperature (∘C)

Tran

sitio

n ra

te (s

minus1)

(a)

10

20

30

40

50

60

70

Qua

ntum

effici

ency

()

400 650600550500450Temperature (∘C)

Mg2TiO4 2 at Eu

(b)





rarr7F356


4 Conclusion



2


2and




Acknowledgments


References











2Ti2O7pyrochlore










2TiO4spinels


















20137ndash20143 2004









2O3and Tb

2O3doped in and




5rdquo



2O3and La(OH)










FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics




200

400

600

800

1000

1200

1400

1600


400 650600550500450Temperature (∘C)

Tran

sitio

n ra

te (s

minus1)

(a)

10

20

30

40

50

60

70

Qua

ntum

effici

ency

()

400 650600550500450Temperature (∘C)

Mg2TiO4 2 at Eu

(b)





rarr7F356


4 Conclusion



2


2and




Acknowledgments


References











2Ti2O7pyrochlore










2TiO4spinels


















20137ndash20143 2004









2O3and Tb

2O3doped in and




5rdquo



2O3and La(OH)










FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics










2TiO4spinels


















20137ndash20143 2004









2O3and Tb

2O3doped in and




5rdquo



2O3and La(OH)










FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics








FluidsJournal of


Journal of










Superconductivity




GravityJournal of








Journal of






Volume 2014


PhotonicsJournal of


Journal of

Biophysics



Documents

Analysis of Eu 3+ Emission from Mg TiO Nanoparticles by ...downloads.hindawi.com/journals/acmp/2015/736517.pdf · 2 transition and with the emission decays varying between . and