GELCASTING ก ˘ˇ ˆ˙ ˝ก ˛˘ ˝ ˚ ˜ !˝˛ก Abstract ) * ˝*+, : ก ...eng.sut.ac.th/research/2015/upload/abstract/49-51/06.pdfGelcasting is a forming process similar to

97

GELCASTING �� ก��ก

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Gelcasting is a forming process similar to slip casting; and can produce complex-shaped ceramic parts similar to injection molding. With high green strength, gelcast parts are strong and can be machined, if needed, before firing. Gelcasting do not involve complex and long debinding steps which are problems with injection molding. Therefore, gelcasting is promissing new technology for complex shape ceramics that are either too complicated or too expensive to be manufactured by other processes.

)�*��*+,� : �� ก AB��ก�� 2548 - �ก�� 2549 ��G� 72-73

98

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Abstract

Color is the first objective thing that exists in the world. It is caused by the interaction of light on a material. This paper overviews what is color and how human visual it. In addition, it reveals the color scale which is an indicator to measure color. Finally, it discloses the color measurement instrument of Suranaree University of Technology.

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99

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100

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101

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103

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104

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105

DAN KWIAN CLAYS FOR SLIP CASTING

Sirirat Rattanachan* School of Ceramic Engineering, Institute of Engineering,

Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand

Abstract In the present study, Dan Kwian clays were characterized and prepared for slip casting. The very high plastic (HP) and mild plastic (MP) Dan Kwian clays were mixed with Ranong kaolin and quartz for preparation of slip casting in various compositions. The relationship between viscosity and sodium silicate used was determined for these slips in the presence of various compositions. The casting rate of slip samples were determined. From the result, it found that the suitable composition of Dan Kwian slips consisted of the HP clay content less than 60% wt of total slip weight. The short casting time of Dan Kwian slips was achieved within 1 hour. It is possible to prepare Dan Kwian clay body for slip casting. Published in : Science Asia 33, 2007, pp. 239-243

106

CHITOSAN-CRYSTALLIZED APATITE COMPOSITES FOR BONE CEMENTS: MECHANICAL

STRENGTH AND SETTING BEHAVIOR

Sirirat Rattanachana, Charussri Lorpayoonb and Piyanan Bunpayunc Institute of Engineering, Suranaree University of Technology, Nakhon Ratchasima, 30000 Thailand

e-mail: [email protected], [email protected] and [email protected]

Abstract Crystallized apatite behaved to plaster of Paris was prepared by the chemical method. Apatite powder was mixed with chitosan. In this study, it was also studied the effect of HA seed and sodium hydrogen phosphate as an additive on their mechanical strength, compared with the normal calcium phosphate cements. Setting time of paste cements was determined using Gillmore method. Phases of cement obtained from a crushed cylinder were analyzed using XRD analysis. From the results, chitosan was effective both in increasing mechanical properties and accelerating hardening of the normal bone cements. Nevertheless, the compressive strength of chitosan-crystallized apatite composites was not significantly improved as compared to the controlled one. In addition, it was found that the mechanical strength of the cements decreased when increasing the concentration of HA seed and an additive. Published in : Proceedings of the 19th International Symposium on Ceramics in Medicine, The Annual Meeting

of the International Society for Ceramics in Medicine, Chengdu, China, October 10-13, 2006. pp. 839

107

CHITOSAN-CALCIUM PHOSPHATE CEMENT COMPOSITES FOR BONE SUBSTITUTES

Sirirat Rattanachan, Charussri Lorprayoon and Piyanan Boonphayak School of Ceramic Engineering, Institute of Engineering, Suranaree University of Technology,

111 University Avenue, Maung, Nakhon Ratchasima, Thailand ([email protected])

Abstract

Calcium phosphate cements were prepared by mixing many calcium phosphate combinations, aqueous solutions of chitosan and studied the effect of the concentration of chitosan on the mechanical strength and setting behavior of cements. Compressive strength and setting time of samples were determined. 5%wt chitosan in acetic acid with cement compositions gave higher the mechanical strength and faster the setting time of cements than aqueous solution. The formation of hydroxyapatite was found in the cements after curing in 100% humidity at 37oC for a week. Published in : Asian Symposium on Materials and Processing 2006, Sofitel Central Plaza Bangkok, Thailand, November 9-10, 2006, Paper D-1. pp. 70

108

SYNTHESIS OF CHITOSAN/BRUSHITE POWDERS FOR BONE CEMENT COMPOSITES

Sirirat Rattanachana, Charussri Lorprayoonb and Piyanan Boonphayakc Institute of Engineering, Suranaree University of Technology, 111 University Avenue

Muang, Nakhon Ratchasima, 30000 THAILAND [email protected], [email protected], [email protected]

Abstract

Recently, calcium phosphate cements have been considered in medicine and dentistry because of their excellent biocompatibility and advantages in situ handling and shaping abilities. Nevertheless, low mechanical strength of these cements limits wider the clinical applications. The aim of this work was the synthesis of chitosan/brushite powders for preparing the calcium phosphate cements. The synthesis of brushite was carried out in the chitosan matrix from calcium chloride and sodium phosphate at moderate pH of 4 and then dried from 60 to 100°C. The obtained powders were characterized by XRD and FT-IR technique. With increasing the drying temperature, phase of dicalcium phosphate anhydrous increased. Moreover, FTIR indicates the bands attributable to chitosan and brushite. The brushite synthesized using this route was used to be a starting powder for calcium phosphate cement (CPC). To prepare CPC, the mixture of chitisan/brushite and α-tricalcium phosphate powders was mixed with water and cured at 100% humidity for 7 days. The compressive strength of the cements was determined to evaluate the potential use for the bone cement. Cements formed with chitosan/brushite dried at 100°C had the greatest compressive strength of all cement tests. The improvement of compressive strength seemed to depend on the affinity of chitosan briding in the cements.

Published in : Archieves of BioCeramics Research Volume 7, Proceeding of the Asian BioCeramics 2007, Osaka, Japan, 25-28 Sep. (2007)

109

LOW TEMPERATURE SYNTHESIS OF CRYSTALLIZED APATITE NANOPARTICLES

P. Boonphayak1 and S. Rattanachan2 School of Ceramic Engineering, Institute of Engineering,

Suranaree University of Technology, 111 University Avenue, Muang District, Nakhon Ratchasima 30000, Thailand

[email protected] and [email protected]

Abstract Apatite nanoparticles were synthesized at low temperature with and without any protection from atmospheric CO2 during the synthesis. The reaction took place at pH 9-10 under stirring for 90 min. After washing gel, it was heat-treated in air up to 400º for 10 h. The obtained powder was characterized by XRD, FT-IR analysis and nanoparticles were observed by TEM. From XRD patterns, the well-crystallized apatite powders were obtained for powder heated up at 300 and 400º. However, carbonate (CO3

2-) was replaced by phosphate (PO4

3-) for powder prepared in vacuum atmospheric after heating at 300 and 400ºC. Nanoparticle size was approximately 20-50 nm and a small amount of needle-like particles were also present. Published in : The 6th Asian Bioceramics Symposium 2006, Sofitel Central Plaza Bangkok, Thailand, November 7-10, 2006, paper no. OB-11. (in CD-Rom format)

110

FATIGUE BEHAVIOR OF Al2O3-BASED COMPOSITE WITH BaTiO3 PIEZOELECTRIC PHASE

Sirirat Rattanachan1, Yukio Miyashita2 and Yoshiharu Mutoh2 1Institute of Engineering, Suranaree University of Technology, Nakorn Ratchasima, Thailand

2Department of Mechanical Engineering, Nagaoka University of Technology 1603-1 Kamitomioka, Nagaoka-shi 940-2188 Japan

Abstract

Fatigue behavior of Al2O3-based composite with BaTiO3 piezoelectric phase was studied by carrying out four-point bending fatigue tests for the poled and unpoled composites, which was compared to that of monolithic Al2O3. Tests were conducted under load ratio of R = 0.1 at frequency of 20 Hz with sinusoidal waveform. The present composites exhibited high fatigue resistance compared to monolithic Al2O3. From the detailed observations, it was found that the improvement of fatigue strength was mainly due to stress-induced domain switching. The relationship between da/dN and Kmax was evaluated by conducting fatigue crack growth tests. The threshold stress intensity factors for unpoled and poled composites were higher than that of monolithic Al2O3. Published in: International Journal of Fatigue, March 2, 2006

111

STABILIZATION OF CERAMIC SLIPS I

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Q��Q��^TYGก�̀��b_#ก��Z�G�� ]��กa��̀�#� b�� (stabilization of ceramic slip) ��^#a�` �� #ก��R�� ]��Y\Y��Qก�� (agglomeration) T��b_#��h�ก�� j��R��Z�G�� ]��a��̀�#� b��h��`�# v ��"R�#��กQ��ก��ก�̀��R��A��AZ�� PQ�Q�Y��TYG�_#aQ`#��A��A��ก�W� 2 �� a�ก (Stabilization of Ceramic Slip I) �h�Q��b_# �� #ก��ก�Y agglomeration a��h�ก��Z�G�� ]��a��̀�#� b��aQQ electrostatic stabilization ��R �# (Stabilization of Ceramic Slip II) A\Yb_#��h�ก��Z�G�� ]��a��̀�#� b��aQQ electrostatic stabilization �`�T��Qa�G�A\Yb_#��h�ก��Z�G�� ]��a��̀�#� b��aQQ steric stabilization a��aQQ electrosteric stabilization

Abstract

Stabilization of ceramic slip is reviewed starting from the cause of agglomeration to important stabilization methods. Due to the fact that this article length is too long to be published in one journal issue, it is divided into 2 parts. Causes of agglomeration and electrostatic stabilization are explained in part one, Stabilization of Ceramic Slip I. Part two, Stabilization of Ceramic Slip II consists of electrostatic stabilization (continue), steric stabilization and electrosteric stabilization.

)�*��*+,� : Suranaree Journal of Science and Technology, Vol 13 No. 3 , 2549, pp 259-270.

112

STABILIZATION OF CERAMIC SLIPS II

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Q��Q��^TYGก�̀��b_#ก��Z�G�� ]��กa��̀�#� b�� (stabilization of ceramic slip) ��^#a�` �� #ก��R�� ]��Y\Y��Qก�� (agglomeration) T��b_#��h�ก�� j��R��Z�G�� ]��a��̀�#� b��h��`�# v ��"R�#��กQ��ก��ก�̀��R��A��AZ��Y��TYG�_#aQ`#��A��A��ก�W� 2 �� R��R#ก��Z�G�� ]��กa��̀�#� b��Z��^�� 1 ( h�� ̀� �ก, 49) �h�Q��b_# �� #ก��ก�Y agglomeration a��h�ก��Z�G�� ]��a��̀�#� b��aQQ Electrostatic stabilization ��R �#ก��Z�G�� ]��กa��̀�#� b��Z��^�� 2 (Stabilization of Ceramic Slip II) ก�̀��b_#��h�ก��Z�G�� ]��a��̀�#� b��aQQ Electrostatic stabilization �`�T��Q a��YG��h�ก��Z�G�� ]��a��̀�#� b��aQQ Steric stabilization a�� Electrosteric stabilization

Abstract

Stabilization of ceramic slip is reviewed starting from the cause of agglomeration to important stabilization methods. Due to the fact that this article is too long to be published in one journal issue, it is divided into 2 parts. Causes of agglomeration and electrostatic stabilization are explained in part one, Stabilization of Ceramic Slip I. Part two, Stabilization of Ceramic Slip II consists of Electrostatic stabilization (continued), Steric stabilization and Electrosteric stabilization.

)�*��*+,� : Suranaree Journal of Science and Technology, Vol 13 No. 3, 2549, pp 271-283.

113

CRITICAL DRYING POINT OF DAN KWIAN POTTERY

S. Sriimsak, W. Luangsiritunya, E. Dungphontong, S. Chaisrihad, P. Sukphoem, W. Boonyarut and N. Pradadking

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Abstract

Dan Kwian pottery is a beautiful and unique pottery which brings both reputation and large amount of income to Nakhon Ratchasima province. However, most of the factories in Dan Kwian district are still using basic production techniques which have been inherited for many decades especially drying technique. At present most factories in Dan Kwian are drying their greenwares in grass-walled huts. This causes not only longer drying time but also the drying period to depend upon the seasons. Critical moisture content of Dan Kwian pottery was studied in this work in order to be used as the data to improve the drying technique of Dan Kwian pottery. It was found that the critical moisture content of Dan Kwian pottery is about 10-15%. Therefore we should be able to decrease the drying time of Dan Kwian pottery by increase its drying rate after its moisture content was reduced to below 10%.

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114

CELADON GLAZE ON DAN KWIAN POTTERY

S. Srilomsak, M. Wonginjun, M. Kanjanasin, R. Ahosi, R. Sittisue, R. Thongkan, L. Udon, and W. Thaitong

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Abstract

Celadon glaze is a unique and attractive green color glaze well known of Chiangmai and Dan Kwian pottery is also a well-known and beautiful red pottery of Nakhon Ratchasima. In this work, ceramic engineering students at Suranaree University of Technology studied twenty one different compositions of Celadon glaze under six different firing conditions on commercial clay samples. Results showed that the more ash content in the compositions the more greenish color of Celadon could be observed. Moreover, firing under reduction atmosphere gave a bluish-green color while firing under oxidation atmosphere resulted in a yellowish-green color. In addition, students accidentally found that Celadon glaze on Dan Kwian pottery under oxidative atmosphere gave a gorgeous black color with brown stripes.

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)�*��*+,� : Suranaree Journal of Science and Technology, Vol 13 No. 2 pp 197-205

115

CELADON GLAZE ON DAN KWIAN POTTERY II

S. Srilimsak, S. Saengwimol, H. Tonkaew, H. Kamsorn, A. Boonmak, O. Kamon-in and A. Promsen

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Abstract Celadon glaze is a unique glaze of Chiangmai province whereas Dan Kwian pottery is a well-known pottery of Nakhon Ratchasima province. The objective of this study was to investigate Celadon glaze on Dan Kwian pottery. Twenty one Celadon glaze formulae were mixed and applied on biscuit samples. The biscuits were then fired at six different firing conditions. Results showed that attractive colors and textures could be obtained if samples were fired in an electric kiln to a maximum temperature of 1,260oC : soaking time for 2 h. In contrast, attractive colors and textures could not be obtained if samples were fired in a wood-fired kiln under the normal firing condition at Dan Kwian. It is recommended to adjust either the glaze formulae or firing conditions if samples were to fire in Dan Kwian wood-fired kiln.

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116

BAROID FILTER PRESS

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@A��A�@"B: Baroid filter, ceramic slip, slip casting, casting rate, permeability

)�*��*+,� : �� ก PQ�Q��R 26 ก.�.S h.�. 2550 ��G� 27-30.

117

EFFECT OF Sr2+ SUBSTITUTION ON DIELECTRIC PROPERTIES

AND PTCR BEHAVIOR OF BaTiO3

Sutham Srilomsak Institute of Engineering Suranaree University of Technology Nakorn Ratchasima 30000

Abstract

Ba1-xSrxTiO3 ceramics have been widely used as electronic materials. However, conflicting results for the effect of Sr2+ for the maximum value of the relative dielectric constant at the Curie point of Ba1-xSrxTiO3 ceramics have been reported. Several researchers have studied the possibility of using Ba1-xSrxTiO3 ceramics as positive temperature coefficient resistivity (PTCR) material but complete information has not been fulfilled. The purposes of this study were to the ascertain the effect of Sr2+ substitution on some dielectric and electrical properties of BaTiO3 and to further investigate the possibility of utilizing Ba1-xSrxTiO3 ceramics as PTCR materials. In this study an X-ray diffractometer and scanning microscope were used to study phases and microstructures of Ba1-xSrxTiO3. In addition, the capacitance and resistance of Ba1-xSrxTiO3 were measured and their relative permittivity and resistivity were calculated and analyzed. Results indicated that Sr2+ substitutions cause the unit cell of Ba1-xSrxTiO3 to shrink and change from a tetragonal to a cubic symmetry. Moreover, Sr2+ substitution shifts the Curie point of Ba1-xSrxTiO3 to a lower temperature. Lastly, pure Ba1-xSrxTiO3 does not display good PTCR characteristics for commercial PTCR material.

Keywords: BaTiO3, dielectric, positive temperature coefficient resistivity, PTCR

Published in : Suranaree Journal of Science and Technology, Vol. 15, No. 1, pp25-32.

118

X-RAY ABSORPTION SPECTROSCOPY STUDY OF Ba1-XSrXTiO3 (X = 0.0-0.2) AT THE Ti-K

AND Ba-LIII EDGES

W. Somphon1 and S. Srilomsak2 1National Synchrotron Research Center, Nakhon Ratchasima 30000

2Institute of Engineering Suranaree University of Technology Nakorn Ratchasima 30000

Abstract

Barium titanate, BaTiO3 is a significant material for electronic components. It was known that Sr2+

substitution on Ba ion can strongly modify ferroelectric properties of BaTiO3 but the structural change has not been fully understood. An X-ray absorption spectroscopy at the Ti K-edge (4966 eV) and the Ba Lm-edge (5247 eV) was employer to investigate the structure of Ba1-xSrxTiO3 (BSTO) with 0<x<0.20. Results suggested that Ba2+ did not change its position with Sr2+ substitution. On the other hand, Ti4+ atoms gradually displaced as Sr2+ is increased. Keywords : X-ray Absorption Spectroscopy, BaTiO3, Ferroelectric, Barium Strontium Titanate Published in : Advanced Materials Research, Vols. 55-57, pp 157-160, (2008).

119

HARMONIC ANALYSIS OF POLARIZATION HYSTERESIS LOOPS OF AGED PZT

S. Srilomsak, W. Schulze, S. Pilgrim and F. Williams Jr. Institute of Engineering Suranaree University of Technology Nakorn Ratchasima 30000

School of Ceramic Engineering and Material Science, Alfred University, Alfred, NY 14802, USA.

Abstract

Lead Zirconate Titanate (PZT) suffers aging which cause its properties to deteriorate. Understanding the aging of PZT is critical to the design of devices. This work used harmonic analysis to study polarization hysteresis loops (PE-loop) of aged PZT. The results indicated that harmonics 1-5 have unique effect on the shape of PE-loops. The changing of these amplitudes and phase angles of these harmonics during aging period caused PE-loops to alter their shapes with time,

Published in: Proceeding of IEEE Int. Ultrasonics, Ferroelectric and Frequency Control 50th Anniversary Joint

Conference. pp 213-216

120

EFFECT OF K2O ON THE CRYSTALLIZATION IN THE Li2O-SiO2 SYSTEM OF GLASS

Shigeki Morimoto School of Ceramic Engineering, Institute of Engineering, Suranaree University of Technology

111 University Avenue, Muang District, Nakhon Ratchasima 30000, Thailand Tel:: (66)44-22-4475, e-mail: [email protected]

Abstract

The effect of a small amount of K2O on the crystallization behavior in the system of Li2O-SiO2 glass was investigated. The Li2O⋅SiO2 and Li2O⋅2SiO2 crystals precipitate simultaneously, but only Li2O⋅2SiO2 crystal grows in the glass without K2O. On the contrary, only Li2O⋅SiO2 crystal starts to precipitate and grow in the glass containing a small amount of K2O below 800°C. It was found that a small amount of K2O affects the mechanism of phase separation and crystallization process, and K2O suppresses the crystallization of Li2O⋅2SiO2, but promotes the precipitation of Li2O⋅SiO2 crystal. Published in : The 46th Symposium on Glasses and Photonic Materials, Glass Division of the Ceramic Society

of Japan, Siga Prefectural University, Hikone, Siga, Japan, November 21-22, 2005, paper no. A03, Proceedings pp.6-7.

121

DECRYSTALLIZATION/AMORPHIZATION OF Li2O-SiO2 TRANSPARENT GLASS-CERAMICS

Chokchai Yatongchai, Shigeki Morimoto School of Ceramic Engineering, Institute of Engineering, Suranaree University of Technology

111 University Avenue, Muang District, Nakhon Ratchasima 30000, Thailand Tel: (66)44-22-4475, e-mail: [email protected]

Abstract

The decrystallization/amorphization phenomenon was investigated in Li2O-SiO2 glass-system by ion exchange. The disappearance of Li2O-SiO2 crystals by Li

+-Na+ and Li+-K+ ion exchange was confirmed by XRD. The ion exchange between foreign ions and Li+ ion in Li2O-SiO2 crystals take place directly, the structure of Li2O-SiO2 crystals collapses and disappears due to the mismatch of crystal structure. Published in: The 46th Symposium on Glasses and Photonic Materials, Glass Division of the Ceramic Society


122

PREPARATION OF GLASS-CERAMICS USING FLY ASH AS A RAW MATERIAL

Waraporn EmEm, Shigeki Morimoto School of Ceramic Engineering, Institute of Engineering, Suranaree University of Technology


Abstract

The fly ash was investigated as one of the starting materials to synthesize wollastonite based glass-ceramics. About 35% of fly ash can be introduced. The crystalline phases were wollastonite for glass with CaF2, and wollastonite and spodumene for glass with CaF2 and spodumene, which exhibit bulk crystallization. The percent crystallinity was about 50%. The fracture strength of glass-ceramics was about 220 MPa, which was two times higher than that of glasses. However, the thermal shock resistance was jut two times higher than that of glass. Thus, the fly ash can be used for glass industry as a raw material. Published in: The 46th Symposium on Glasses and Photonic Materials, Glass Division of the Ceramic Society


123

EFFECT OF K2O ON CRYSTALLIZATION OF Li2O-SiO2 GLASS

Shigeki Morimoto School of Ceramic Engineering, Institute of Engineering, Suranaree University of Technology

111 University Avenue, Muang District, Nakhon Ratchasima 30000, Thailand Tel:: (66)44-22-4475, e-mail: [email protected]

Abstract

The effect of a small amount of K2O on the crystallization behavior in the system of Li2O-SiO2 glass was investigated. Lithium metalicate (Li2O⋅SiO2, LS) and lithium disilicate (Li2O⋅2SiO2 L2S) crystals precipitate simultaneously, but only L2S crystal grows upon further heat treatment in the glass without K2O (Li-glass). In the glass containing a small amount of K2O (K3 glass), only LS crystals precipitate and grow. The stable crystalline phases are L2S and SiO2 crystals in both glasses. Phase separation was observed before crystallization; a Li2O-rich phase formed an isolated droplet phase in Li-glass and the continuous phase in K3 glass. The Li+-K+ ion exchange test confirmed these structures. [SEM-EDX] analysis confirmed K2O exists in Li2O-rich phase after phase separation in K3 glass. Thus, K3 glass separates into two phases, one of which is a continuous phase rich in Li2O and containing considerable amount of K2O. The LS crystal precipitates and grows in this phase upon further heat treatment. Consequently, K2O suppresses the crystallization of L2S and promotes the precipitation of LS crystals. Keywords: Li2O-SiO2 glass, Phase separation, Crystallization, Lithium disilicate, Lithium metasilicate, K2O Published in: Journal of the Ceramics Society of Japan, 114 (2006) 195-198.

124

STRENGTHENING OF Li2O⋅⋅⋅⋅2SiO2 TRANSPARENT GLASS-CERAMICS BY ION EXCHANGE

Chokchai Yatongchai, Shigeki Morimoto School of Ceramic Engineering, Institute of Engineering, Suranaree University of Technology


Abstract

The chemical strengthening of Li2O⋅2SiO2 transparent glass-ceramics was investigated. The fracture strength of glass and glass-cermicas increased first and then decreased, and the crack formation and peeling of ion exchanged layer are observed for both Li+-Na+ and Li+-K+ ion exchange. This suggests that the submicroscopic crack generates perpendicular to the surface when the ion exchanged layer peels off the surface. The volume change by Li+-Na+ and Li+-K+ ion exchange is very large, over 10%, this large volume change causes the peeling and crack formation of ion exchanged layer despite in which compressive stress arise. In the early stage of ion exchange, the compressive stress arisen affects effectively on the increase in strength. However, as increases in the thickness of ion exchanged layer, the volume change of ion exchanged layer can not be neglected, and crack and peeling may generate in that layer. Finally, the fracture strength decreases.

Keywords: Transparent glass-ceramics, Ion exchange, XRD, Li2O⋅2SiO2 crystal, Crowding Published in: Journal of the Ceramics Society of Japan, 114 (2006) 227-229.

125

PHASE SEPARATION AND CRYSTALLIZATION IN THE SYSTEM SiO2-Al2O3-P2O5-B2O3-Na2O GLASSES

Shigeki Morimoto

School of Ceramic Engineering, Institute of Engineering, Suranaree University of Technology 111 University Avenue, Muang District, Nakhon Ratchasima 30000, Thailand

Tel: (66)44-22-4475, e-mail: [email protected]

Abstract The phase separation and crystallization in the system (80-X)SiO2-X(Al2O3+2O5)-5-B2O3-15Na2O (mol%) glasses was investigated. Glasses with X=20 and 30 phase separated into two phases, one of which is rich in SiO2-Al2O3-P2O5 and form a continuous phase. Glasses containing a larger amount of Al2O3-P2O5 (X=40 and 50) readily crystallize and precipitates tridymite type AlPO4 crystals. It is estimated that the phase separation occurs forming continuous SiO2-Al2O3-P2O5 phase at first, and then tridymite type AlPO4 crystals precipitate and grow in this phase. Highly transparent glass-ceramics comparable to glass can be obtained by controlling heat treatment precisely. The crystal size and percent crystallinity of these transparent glass-ceramics are 20-30 nm and about 50%, respectively. Keywords: Crystallization, Glass-ceramics, Nucleation, Crystals, Nanocrystals, Optical properties, Oxide

glasses, Alkali silicate, Phases and equilibria Published in: Journal of Non-Crystalline Solids, 352 (2006) 756-760.

126

ABSORPTION AND EMISSION SPECTRA OF Ni-DOPED GLASSES AND GLASS-CERAMICS IN CONNECTION WITH ITS CO-ORDINATION NUMBER

Sasithorn Khonthon, Shigeki Morimoto and Yasutake Ohishi*

School of Ceramic Engineering, Institute of Engineering, Suranaree University of Technology 111 University Avenue, Muang District, Nakhon Ratchasima 30000, Thailand

*Department of Future-oriented Basic Science and Materials, Toyota Technological Institute, 2-12-1, Hisakata, Tempaku-ku, Nagoya-shi 468-8511, Japan


Abstract The absorption and emission spectra of Ni-doped glasses and transparent glass-ceramics are discussed

in relation to its coordination number. The results evidenced that the color changed drastically to deep pink from yellow for the lithium metasilicate crystal based transparent glass-ceramics and to blue from brown for the spinel crystal based transparent glass-ceramics after crystallization, respectively. The absorption spectra of lithium metasilicate and spinel glasses suggest the existence of a tetrahedral Ni2+ ion and trigonal bipyramid Ni2+ ion. On the contrary, tetrahedral Ni2+ ions in the lithium metasilicate transparent glass-ceramics and the octahedral Ni2+ ion in spinel transparent glass-ceramics are dominant. The emission at around 580 nm was observed in spinel transparent glass-ceramics under the excitation of 380 nm, however, a very weak or no emission was observed in the lithium metasilicate glass, lithium metasilicate transparent glass-ceramics and spinel glass under the excitation of 430 nm. This emission might be due to 1T1(D)→

3A2(F) transition after the excitation from 3A2(F) to

3T1(P) of the octahedral Ni2+ ions. In addition, only spinel transparent glass-ceramics

exhibits a broad NIR emission at around 1220 nm under the excitation of 974 laser diode. This emission may be due to 3T2(F) →

3A2(F) transition. It is considered that the tetrahedral Ni2+ ion is located between the chains in

the lithium metasilicate crystal. Keywords: Ni2+ ion, Transparent glass-ceramics, Absorption spectra, VIS-NIR emission spectra, Coordination

Number Published in: Journal of the Ceramic Society of Japan, 114 (2006) 791-794.

127

PREPARATION OF GLASS-CERAMICS USING FLY ASH AS A RAW MATERIAL

Waraporn Emem and Shigeki Morimoto School of Ceramic Engineering, Institute of Engineering, Suranaree University of Technology


Abstract

The possibility of effective utilization of fly ash originated from a coal burning thermal power plant was investigated as one of the starting materials to synthesize wollastonite-based glass-ceramics. About 35% of fly ash was introduced into a batch as a raw material, and bubble-free and dark green glasses were obtained. The glass free from CaF2 or spodumene showed surface crystallization; however, glass containing CaF2 and/or spodumenen exhibited bulk crystallization. The crystalline phases were wollastonite for glass with CaF2 and wollastonite and spodumene for glass with CaF2 and spodumene. The percent crystallinity was about 50%. The fracture strength of glass-ceramics was about 220 MPa, which was two times higher that that of the original glass, and the surface hardness might be high, resulting in a scratch-free surface. However, thermal expansion coefficient did not change with crystallization, and hence the thermal shock resistance was presumed to be 2 times higher than that of original glass. Thus, fly ash supplied from a coal burning thermal power plan could be used for glass-ceramics as a raw material. Keywords: Fly ash, glass, crystallization, glass-ceramics, wollastonite Published in: Suranaree Journal of Science and Technology13 (2006) 137-142.

128

LUMINESCENCE CHARACTERISTICS OF Ni2+ ION-DOPED GLASSES AND GLASS-CERAMICS IN RELATION TO ITS COORDINATION NUMBER

Sasithorn Khonthona, Shigeki Morimotoa and Yasutake Ohishib

aSchool of Ceramic Engineering, Institute of Engineering, Suranaree University of Technology 111 University Avenue, Muang District, Nakhon Ratchasima 30000, Thailand

bDepartment of Future-oriented Basic Science and Materials, Toyota Technological Institute, 2-12-1, Hisakata, Tempaku-ku, Nagoya-shi 468-8511, Japan


Abstract Ni2+ ions occupy the tetrahedral (4), trigonal bipyramid (5) and octahedral (6) sites in glasses and

glass-ceramics. The color changes depending on coordination number, typically pink for tetrahedral site, brown for trigonal bipyramidal and tetrahedral site, green to blue for octahedral site, respectively. The broad NIR emission peaking at around 1220 nm was observed only for octahedral Ni2+ ions. This emission is due to 3T2(F) → 3A2(F) transition.

Published in: Asian Symposium on Materials and Processing 2006 (ASMP 2006), Bangkok, Thailand, November 9-10, 2006, paper No. A-16, Proceedings pp. 16. Journal of Solid Mechanics and Materials Engineering, 1 (2007) 439-446.

129

LUMINESCENCE CHARACTERISTICS OF Se-, Te- AND Bi-DOPED GLASSES AND GLASS-CERAMICS

Shigeki Morimotoa, Sasithorn Khonthona and Yasutake Ohishib




Abstract The origin of coloration and luminescence of Se-, Te- and Bi-doped glasses and glass-ceramics were

investigated. NIR luminescence was observed at around 1100 nm and 1200 nm in Bi-doped and Te-doped glasses and glass-ceramics, respectively. On the contrary, no NIR luminescence could be observed in Se-doped glass. It is suggested that the origin of coloration and NIR luminescence in these hosts is most likely caused by molecular Se2 (Se2

-), Te2 (Te2-) and Bi2 (Bi2

-). Published in: Asian Symposium on Materials and Processing 2006 (ASMP 2006), Bangkok, Thailand, November 9-10, 2006, paper No. A-17, Proceedings pp. 17.

130

LUMINESCENCE CHARACTERISTICS OF Te- AND Bi-DOPED GLASSES AND GLASS-CERAMICS





Abstract The origin of coloration and luminescence of Te- and Bi-doped glasses and glass-ceramics were

investigated. The broad NIR luminescence was observed in both glasses and glass-ceramics ranging 1000-1600 nm. It is suggested that the origin of coloration and NIR luminescence in these hosts is most likely caused by molecular Te2 (Te2

-) and Bi2 (Bi2-).

Published in: The 47th Symposium on Glasses and Photonic Materials, Glass Division of the Ceramic Society

of Japan, Tokyo University of Science, Noda, Chiba, Japan, November 21-22, 2006, paper no. 2A-09, Proceedings , November 9-10, 2006, paper No. A-17, Proceedings pp. 61-62.

131

LUMINESCENCE CHARACTERISTICS OF Se-DOPED GLASS

Sasithorn Khonthona, Shigeki Morimotoa and Yasutake Ohishib aSchool of Ceramic Engineering, Institute of Engineering, Suranaree University of Technology

111 University Avenue, Muang District, Nakhon Ratchasima 30000, Thailand bDepartment of Future-oriented Basic Science and Materials, Toyota Technological Institute,

2-12-1, Hisakata, Tempaku-ku, Nagoya-shi 468-8511, Japan Tel: (66)44-22-4475, e-mail: [email protected]

Abstract

The optical absorption and luminescence characteristics of Se-doped soda-lime-silicate glasses were investigated. The VIS luminescence was observed at around 650 and 750 nm. However, NIR lumescence can not be detected unlike Te-doped glasses. The coloration and luminescence are derived from molecular Se, such as Se2 (Se2

-).

Published in: The 47th Symposium on Glasses and Photonic Materials, Glass Division of the Ceramic Society of Japan, Tokyo University of Science, Noda, Chiba, Japan, November 21-22, 2006, paper no. 2A09, Proceedings , November 9-10, 2006, paper no. P1. Proceedings pp. 27-28.

132

IS TETRAHEDRALLY COORDINATED Cr3+ ION POSSIBLE IN GLASSES AND GLASS-CERAMICS?





Abstract It is well known that Cr3+ ions occupy preferentially octahedral sites due to the strong ligand field

stabilization energy. The color and absorption spectra of Cr3+ ion doped Li2O⋅SiO2 glass change drastically after crystallization. Analytical results suggest the existence of tetrahedrally coordinated Cr3+ ions in lithium metasilicate crystals (Li2O⋅SiO2).

Published in: The 47th Symposium on Glasses and Photonic Materials, Glass Division of the Ceramic Society

of Japan, Tokyo University of Science, Noda, Chiba, Japan, November 21-22, 2006, paper no. 2A-09, Proceedings , November 9-10, 2006, paper no. P2, Proceedings pp.29-30.

133

LUMINESCENCE CHARACTERISTICS OF Te- AND Bi-DOPED GLASSES AND GLASS-CERAMICS

Sasithorn Khonthona, Shigeki Morimotoa, Yusuke Araib and Yasutake Ohishib




Abstract The luminescence characteristics of Te- and Bi-doped glasses and glass-ceramics were investigated

and the origin of coloration and near infrared luminescence was discussed. The coloration of these glasses and glass-ceramics might be due to the elemental clustering, such as Te2/Te2

- and Bi2/Bi2-. The broad near infrared

(NIR) luminescence can be detected in Te- and Bi-doped glasses and glass-ceramics. The electron spin resonance (ESR) signal at g≈2.0 was observed in Te- and Bi-doped glasses and glass-ceramics, which exhibit NIR luminescence, and therefore this ESR signal is strongly related to the NIR luminescence. The signal at g≈2.0 might be derived from molecular ions of Te and Bi, Te2

- and Bi2-. Consequently, it is suggested that the

broad NIR luminescence of Te- and Bi-doped glasses and glass-ceramics are most likely to be caused by elemental clustering, such as Te2/Te2

- and Bi2/Bi2-.

Keywords: Tellurium, Bismuth, Clustering, Transparent glass-ceramics, Absorption spectra, NIR

luminescence, ESR Published in: Journal of the Ceramic Society of Japan, 115 (2007) 259-263.

134

ULTRABROADBAND NEAR- INFRARED EMISSION FROM A COLORLESS BISMUTH-DOPED GLASS

Yusuke Araia Takenobu Suzukia, Yasutake Ohishia, Shigeki Morimotob and Sasithorn Khonthonb

aResearch Center for Advanced Photon Technology, Toyota Technological Institute 2-12-1 Hisakata, Tempaku, Nagoya 468-8511, Japan

bSchool of Ceramic Engineering, Institute of Engineering, Suranaree University of Technology 111 University Avenue, Muang District, Nakhon Ratchasima 30000, Thailand


Abstract The characteristics of bismuth-doped glasses were investigated as colorless ultrabroadband near-

infrared gain media. The colorless Bi-doped soda-lime-silicate glass was prepared under controlled redox conditions, and it realized the broadest near-infrared emission of about 600 nm in full width at half maximum, centered at 1000 nm, under 720 nm excitation. The emission band centered toward shorter wavelengths compared with the shortest wavelength for the Bi-doped glass ever reported. The colorless Bi-doped glass developed in this work has a good potential for the broadband gain media for amplifiers and tunable lasers. Published in: Applied Physics Letters, 90 (2007) 26110 (1-3).

135

NEAR INFRARED LUMINESCENCE FROM Bi-DOPED SODA-LIME-SILICATE GLASSES

Sasithorn Khonthon1, Shigeki Morimoto1, Yusuke Arai2 and Yasutake Ohishi2 1School of Ceramic Engineering, Institute of Engineering, Suranaree University of Technology

111 University Avenue, Muang District, Nakhon Ratchasima 30000, Thailand 2Department of Future-oriented Basic Science and Materials, Toyota Technological Institute

2-12-1 Hisakata, Tempaku, Nagoya 468-8511, Japan Tel: (66)44-22-4475, e-mail: [email protected]

Abstract

The effect of melting atmosphere on the luminescent characteristics of Bi-doped soda-lime-silicate glasses was investigated, and the origin of NIR luminescence was also discussed. The appearance of these glasses changed from colorless and transparent to deep brown depending on the melting atmosphere (amount of carbon addition). The characteristic absorption bands can not be observed in all glasses. The colorless and transparent glass (C1.5) exhibit both UV-VIS and NIR luminescence. The UV-VIS luminescence comes from Bi3+ ion, which remains in glasses. On the contrary, the NIR luminescence is derived from Bi clustering, such as Bi2 or Bi2

-, and therefore transparent colorless C1.5 glass contains both Bi3+ and Bi2 or Bi2-. The ESR

measurements confirmed that the ESR signals derived from molecular clustering of Bi, Bi2- can be detected at

g≈2.0. Consequently, it is found that the molecular clustering of Bi, Bi2 or Bi2-, might be produced under the

mild reducing condition. Keywords: Bismuth cluster, soda-lime-silicate glass, Absorption spectra, Near infrared luminescence (NIR),

electron spin resonance (ESR)

Published in: Suranaree Journal of Science and Technology, 14 (2007) 141-146.

136

TELLURIUM ION-DOPED TRANSPARENT GLASS-CERAMICS AS A NOVEL ACTIVE MEDIA FOR BROADBAND NEAR-INFRARED AMPLIFIERS

Yusuke Arai1 Takenobu Suzuki1, Yasutake Ohishi1 and Shigeki Morimoto2

1Research Center for Advanced Photon Technology, Toyota Technological Institute 2-12-1 Hisakata, Tempaku, Nagoya 468-8511, Japan

2School of Ceramic Engineering, Institute of Engineering, Suranaree University of Technology 111 University Avenue, Muang District, Nakhon Ratchasima 30000, Thailand


Abstract Broadband amplifiers in near-infrared region are key devices for the wavelength-division-

multiplexing (WDM) network systems. Much work has been done to realize optical amplifications for WDM use using rare-earth-doped fibers and fiber Raman amplifiers, and to develop new broadband gain media is still desired. We report it for the first time to our knowledge that we have observed broad near-infrared emission from tellurium ion-doped transparent glass-ceramics (Te-spinel glass). The Te-spinel glasses aere prepared by a conventional melt-quenching method, and subsequently heating at 800°CS10hrs and 1000°CS5hrs for nucleation and crystallization. Both of as-prepared glasses and post-annealed glass-ceramics had good transparency in the visible to near-infrared region. Broad fluorescence, with a full width half maximum of about 250 nm and centered at 1250 nm, was confirmed under 974 nm laser excitation. The fluorescence life time τ at 300K was about 600µsec. It lengthened by decreasing temperature, and τ=1.0-1.2msec. was observed in 5-200K. We shows that the Te-spinel glasses have a potential for the novel broadband gain media for amplifiers and tunable lasers. Published in: The 21st International Congress on Glass, Strasburg, France, July 1-6, 2007, paper no M6.

137

MELTING TEMPERATURE AND GLASS COMPOSITION DEPENDENCE ON THE NIR LUMINESCENCE CHARACTERISTICS OF Bi-CONTAINING BORATE GLASSES

Sasithorn Khonthon1, Shigeki Morimoto1, Yusuke Arai2 and Yasutake Ohishi2

1School of Ceramic Engineering, Institute of Engineering, Suranaree University of Technology 111 University Avenue, Muang District, Nakhon Ratchasima 30000, Thailand

2 Research Center for Advanced Photon Technology, Toyota Technological Institute 2-12-1 Hisakata, Tempaku, Nagoya 468-8511, Japan


Abstract Melting temperature and glass composition dependence on the NIR luminescence characteristics of

Bi-containing borate glasses were investigated based on redox reaction. It was suggested that color center and luminescent center seems to be Bi clusters, such as Bi, Bi2, Bi2

-, etc. Published in: The 48th Symposium on Glasses and Photonic Materials, Glass Division of The Ceramic Society

of Japan, Toyohasi University of Technology, Aichi, Japan, November 29-30, 2007, paper no. 1A02, Proceedings pp.2-3.

138

NEAR-INFRARED LUMINESCENT CENTER OF Te-CONTAINING GLASSES

Sasithorn Khonthon1, Shigeki Morimoto1, Penprapa Punpai1, Yusuke Arai2 and Yasutake Ohishi2 1School of Ceramic Engineering, Institute of Engineering, Suranaree University of Technology

111 University Avenue, Muang District, Nakhon Ratchasima 30000, Thailand 2 Research Center for Advanced Photon Technology, Toyota Technological Institute


Abstract

The near-infrared luminescent center of Te-doped glasses was investigated by optical absorption and NIR luminescent measurement. The NIR luminescence can be detected in some limited glasses. It was suggested that the NIR luminescent center might be Te2

-. Published in: The 48th Symposium on Glasses and Photonic Materials, Glass Division of The Ceramic Society

of Japan, Toyohasi University of Technology, Aichi, Japan, November 29-30, 2007, paper no. 1A02, Proceedings pp.40-41.

139

ON THE NIR LUMINESCENT CHARACTERISTICS OF Bi2O3 CONTAINING BORATE GLASSES

Sasithorn Khonthon1, Shigeki Morimoto1, Yusuke Arai2, Takenobu Suzuki2 and Yasutake Ohishi2 1School of Ceramic Engineering, Institute of Engineering, Suranaree University of Technology



Abstract

The effects of melting temperature and glass composition on the NIR luminescent characteristics of 90[(80-X)B2O310Al2O310ZnOXK2O]10Bi2O3 (X=0-30 mol%) glasses are investigated and the color center and luminescent center of these glasses are discussed based on redox reaction. It was found that the coloration and near-infrared luminescent characteristics of glasses are strongly affected by melting temperature and glass composition. The color becomes deeper with increasing melting temperature and finally metal colloids precipitate being black color. The same tendency can be observed in composition series, higher NIR luminescent intensity with lower K2O content. Near-infrared luminescence starts to appear, reach the maximum intensity and finally disappear with increasing temperature and decreasing alkali content. Thus the luminescent characteristics of Bi-containing borate glasses are found to be influenced strongly by redox reaction of Bi and the highest luminescent intensity might be obtained in the glass just before the beginning of darkening effect (formation process of Bi metallic colloid). It was suggested that the color center and near-infrared luminescent center is likely to be caused by Bi clusters, such as Bi, Bi2, Bi2

-, Bi3, Bi4, etc. Keywords: Bismuth, Borate glass, Melting temperature, Darkening effect, Bi clusters Published in: Siam Physics Congress 2008 (SPC 2008), Khao Yai, Nakhon Ratchasima, Thailand, March 20-

22, 2008, paper no. A-5. Proceedings PP. 16.

140

NEAR-INFRARED LUMINESCENCE CENTER OF Te-DOPED SODA-LIME SILICATE GLASSES

Penprapa Punpai1, Shigeki Morimoto1, Sasithorn Khonthon1, Yusuke Arai2 and Yasutake Ohishi2 1School of Ceramic Engineering, Institute of Engineering, Suranaree University of Technology



Abstract

The effects of carbon addition and TeO2 concentration on the near-infrared (NIR) luminescent characteristics of Te-doped soda-lime-silicate glasses were investigated. Three absorption bands were detected at around 330-380 nm, ∼430 nm and ∼630 nm, respectively. The last absorption band (∼630 nm) has been ascribed to 2Πg→2

Πu transition of Te2-. The NIR luminescence centered at 1200 nm was detected under the

excitation of 974 nm laser diode except for glass of lower carbon addition. The NIR luminescence was found to be strongly affected by melting atmosphere and TeO2 concentration. It is considered that the absorption band, 630 nm, is related strongly to the NIR luminescence of Te-doped soda-lime-silicate glasses. Consequently, it is suggested that the origin of NIR luminescence detected in Te-doped soda-lime-silicate glasses is likely to be caused by Te2

- center. Keywords: Tellurium, soda-lime-silicate glass, color center, NIR luminescent center, clusters Published in: Siam Physics Congress 2008 (SPC 2008), Khao Yai, Nakhon Ratchasima, Thailand, March 20-22, 2008, paper no. PA-28 Proceedings PP. 54.

141

OPTICAL PROPERTIES OF Cr3+ ION IN LITHIUM METASILICATE Li2O⋅⋅⋅⋅SiO2 TRANSPARENT GLASS-CERAMICS



b Research Center for Advanced Photon Technology, Toyota Technological Institute 2-12-1 Hisakata, Tempaku, Nagoya 468-8511, Japan


Abstract The optical properties of Cr3+ ions in lithium metasilicate (Li2O⋅SiO2) transparent glass-ceramics were

investigated. The main crystalline phases precipitated was lithium metasilicate (Li2O⋅SiO2) crystal. The percent crystallinity and crystalline size were ranging 65-75% and 20-35 nm, respectively. The color changes drastically to deep pink from emerald green upon crystallization. New and strong absorption bands appeared and the absorption intensity increases by about 10 times that in glass. These new absorption bands are found to be derived from Cr3+ ions in octahedral sites in lithium metasilicate crystal lattice. Cr3+ ions substitutes for three Li+ ions and occupy distorted octahedral site between single [SiO4]n chains of lithium metasilicate crystal. The ligand field parameters can be estimated: 10Dq = 13088 cm-1, B = 453 cm-1, Dq/B = 2.89 and C = 2036 cm-1. The near-infrared luminescence centered at 1250 nm was not detected in the deep pink glass-ceramics unlike emerald green glass. Keywords: Glas-ceramics, Optical spectroscopy, Nanocrystals, Nanoparticles, Absorption, Luminescence,

Alkali silicates, Electron spin resonance Published in: Journal of Non-Crystalline Solids, 534 (2008) 3343-3347.

142

ON THE NEAR-INFRARED LUMINESCENCE FROM TeO2 CONTAINING BORATE GLASSES Sasithorn Khonthon, Penprapa Punpai, Shigeki Morimoto, Yusuke Arai*, Takenobu Suzuki* and Yasutake

Ohishi* School of Ceramic Engineering, Institute of Engineering, Suranaree University of Technology

111 University Avenue, Muang District, Nakhon Ratchasima 30000, Thailand *Research Center for Advanced Photon Technology, Toyota Technological Institute


Abstract

The effects of melting temperature and glass composition on the near-infrared (NIR) luminescent characteristics of Te-containing borate glasses were investigated and compared with previous works. Three absorption bands were detected at around ∼370 nm, ∼430 nm and ∼530 nm, however, the absorption band at around ∼600 nm could not be detected in all borate glasses. And no NIR luminescence was observed under the excitation of a 974 nm laser diode. The NIR luminescence was observed in Te-green and Te-purple glasses, which showed the absorption band at around ∼600 nm. This absorption band was ascribed to 2Πg→2

Πu transition of Te2

-. Consequently, it is suggested that the origin of NIR luminescence detected in Te-doped soda-lime-silicate glasses is likely to be caused by Te2

- center. Keywords: Tellurium, Borate gass, color center, NIR luminescence, Clusters Published in: Journal of the Ceramic Society of Japan, 116 (2008) 829-831.

143

EFFECTS OF Sn DOPED CERIA ON THE PHASE, MICROSTRUCTURE AND THERMAL EXPANSION

Sutin Kuharuangronga*, Sumittra Charojrochkulb

aCeramic Engineering, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand bNational Metal and Materials Technology Center, Patumthani 12120, Thailand

Abstract

Ceria based electrolytes show ionic conductivity suitable for an intermediate temperature fuel cell. Their ionic conductivity is enhanced with an addition of lower valence cations, resulting from the formation of oxygen vacancy defects related to the dopant and the amount present. In this work, Sn selected as a cation dopant affects the phase, microstructure and thermal expansion coefficient. The results show 10 mol%Sn doped ceria tends to form a second phase. From SEM photomicrographs, an increasing amount of Sn decreases the grain size but increases the porosity. Sn also reduces the thermal expansion coefficient and bulk conductivity of ceria. Keywords: B. Microstructure-final, D. Ceria, E. Fuel cells Published in : The 5th Asian Meeting on Electroceramics, Bangkok, Thailand, 10-14 December 2006

144

EFFECTS OF Sr2+ AND W6+ ON PROPERTIES OF La2Mo2O9-δ

Witoon Thepsuwan1 and Sutin Kuharuangrong2 1School of Ceramic Engineering, Suranaree University of Technology, Nakhon Ratchasima 30000

Phone 08-9173-6811, E-Mail: [email protected] 2School of Ceramic Engineering, Suranaree University of Technology, Nakhon Ratchasima 30000

Phone 0-4422-4470, E-Mail: [email protected]

Abstract Properties of La2-xSrxMo2-yWyO9-δ (x = 0-0.2, y = 0-0.3) synthesized via solid state reaction method

have been investigated. The results of XRD show a single phase of La2Mo2O9 after calcination at 950 oC. The

phase transition temperatures from α to β phase of La2Mo2O9 and La1.9Sr0.1Mo2O9 occur around 557 oC and

560 oC, respectively. A substitute of 7.5 mol% of W6+ into Mo6+ can suppress the α phase. The average grain size of sintered compositions increases with the amount of Sr but slightly decreases with an addition of W. The conductivity value of La1.9Sr0.1Mo2O9 at 540

oC is 6.75 x 10-3 S·cm-1. Above the phase transition temperature, β- La2Mo2O9 shows the highest conductivity and its value at 700

oC is 7.66 x 10-2 S·cm-1. Keywords: La2Mo2O9; Electrolyte for SOFC Published in : The 5th Thailand materials science and technology conference�s book, year 2008, pages 386-388

145

IONIC CONDUCTIVITY OF Sm, Gd, Dy AND Er-DOPED CERIA

Sutin Kuharuangrong* School of Ceramic Engineering, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand

Abstract

Ceria-based materials are prospective electrolytes for intermediate-temperature solid oxide fuel cells. The ionic conductivities of ceria-doped with Sm, Gd, Dy and Er are investigated as a function of temperature by using a.c. impedance. The results show that conductivity depends on the rare earth dopant, its amount, an appearance of second phase, and the microstructure. With 10 mol% dopant, Sm exhibits higher conductivity than Gd, Dy and Er, respectively. With an increase in Dy content, the total conductivity increases, which is attributed to an increase in grain boundary conductivity. By contrast, an increasing amount of Er from 10 to 20 mol% reduces the conductivity of ceria and results in a separated phase of Er2O3 as detected by X-ray diffraction and scanning electron microscopy. In addition, the grain size corresponding to grain boundary density affects the conductivity due to the contributions from the grain interior and grain boundary conductivities. Keywords: Ceria; Intermediate-temperature; Solid oxide fuel cell; Ionic conductivity; Electrical conductivity;

Electrolyte; Rare earth dopants Published in : Journal of Power Sources, year 2007, volume 171, pages 506S510.

146

La, K AND Nb-DOPED-0.90(Bi0.5Na0.5TiO3)-0.10PbTiO3

Sutin Kuharuangrong

School of Ceramic Engineering, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand

Abstract Lanthanum, Potassium and Niobium have been selected as cation dopants to modify the relaxor characteristics of 0.90(Bi0.5Na0.5TiO3)-0.10PbTiO3. The experimental results show that La lowers the phase transition temperatures and decreases the grain size. In contrast, the grain size of K-doped composition tends to increase. Furthermore, the maximum of dielectric permittivity and the Curie temperature increase as compared to those of La-doped material. La can improve the broadness of dielectric permittivity of 0.90(Bi0.5Na0.5TiO3)-0.10PbTiO3. However, Nb is a better promising dopant for enhancing the relaxor behavior for this composition.

Keywords: C. Dielectric properties; Bismuth sodium titanate; Relaxor Published in : Ceramics International, year 2007, volume 33, pages 1403S1407.

147

SYNTHESIS AND PHYSICAL PROPERTIES OF RUDDLESDEN-POPPER PHASE La3-XSrXNi2O7±δδδδ

Wassayamon Singkha1 and Sutin Kuharuangrong2

1School of Ceramic Engineering, Suranaree University of Technology, Nakhon Ratchasima 30000 Phone 08-1780-5072, E-Mail: [email protected]

2School of Ceramic Engineering, Suranaree University of Technology, Nakhon Ratchasima 30000 Phone 0-4422-4474, E-Mail: [email protected]

Abstract

A series of La3-xSrxNi2O7±δ (x = 0, 0.1, 0.3, 0.5 and 1) synthesized by gel combustion method are

investigated as a potential cathode material for IT-SOFC. A partial substitution of lanthanum by strontium in La2.9Sr0.1Ni2O7±δ

shows a lower TEC value and higher electrical conductivity than La3Ni2O7±δ. The further

addition of strontium leads to the formation of the n = 1 RP phase and the second phase of NiO, which result in lower electrical conductivity than La3Ni2O7±δ

phase.

Keyword : Cathode, Ruddlesden-Popper Published in : The 5th Thailand materials science and technology conference�s book, year 2008, pages 35-37

148

SYNTHESIS AND STRUCTURAL ANALYSIS OF La3-XSrXNi2-YFeYO7-δδδδ

Wassayamon Singkhaa,* , Sutin Kuharuangronga

a School of Ceramic Engineering, Suranaree University of Technology, Nakhon Ratchasima, 30000, Thailand E-mail : [email protected]

Abstract

The Ruddlesden-Popper (RP) nickelate, Lan+1NinO3n+1 based material, is a good candidate as an alternative cathode for intermediate temperature SOFC. In this work, La3Ni2O7-δ is synthesized via carbonate precipitation. The effects of Sr and Fe as dopants on the La and Ni sites of the RP phase will be presented on the phase during synthesis and microstructure characterization by means of thermal analysis, x-ray diffraction and scanning electron microscopy. The oxidation states of Ni and Fe will be exhibited by x-ray absorption near edge spectroscopy (XANES) at the K edges of both cations. Keywords: A: Chemical preparation; B: Ruddlesden-Popper; E: Fuel cell Published in : Conference The 5th Asian Meeting on Electroceramics, Bangkok, Thailand, 10-14 December

2006

149

X-RAY ABSORPTION FINE STRUCTURE OF Sm-DOPED CeO2 SYNTHESIZED VIA COPRECIPITATION

Pannee Lawudomphana,* , Sutin Kuharuangronga

a School of Ceramic Engineering, Suranaree University of Technology, Nakhon Ratchasima, 30000, Thailand E-mail: [email protected]

Abstract

Sm-doped CeO2 fuel cell is synthesized via coprecipitation method using nitrates as starting salts. Ammonium hydrogen carbonate, ammonium carbonate and hexamethylenetetramine are used as the precipitants. The comparisons between these precipitants will be presented in terms of the reaction temperature, sintering temperature and particle morphology. In addition, the oxidation states of Ce and Sm affecting the formation of oxygen vacancy will be performed by x-ray absorption near edge spectroscopy (XANES) at the LIII- edges of both cations. The additional information on the local geometric structure around Ce and Sm related to the interatomic distance and coordination number is determined by extended x-ray absorption fine structure (EXAFS). Keywords: A: Chemical preparation; B: Spectroscopy; E: Fuel cell Published in : The 5th Asian Meeting on Electroceramics, Bangkok, Thailand, 10-14 December 2006

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