K2O-MgO-Al2O3 삼성분계에서 K(+)-β/β"-Al2O3의 고온상관계 및 치밀화에 관한 연구

김우성; 함철환; 임성기; Woo Sung Kim; Choul Hwan Ham; Sung Ki Lim

Journal of the Korean Industrial and Engineering Chemistry, Vol.12, No.1, 16-21, February, 2001

A Study on the High Temperature Phase Relations and the Densification of K(+)-β/β" -Al2O3 Ceramics in the Ternary System K2O-MgO-Al2O3

김우성 ^†, 함철환, 임성기

건국대학교 신소재공학과, 서울 143-701

Woo Sung Kim^†, Choul Hwan Ham, and Sung Ki Lim

Department of Materials Chemistry and Engineering, Konkuk University, Seoul 143-701, Korea

E-mail:

초록

삼성분계인 K2O-MgO-Al2O3계로부터 직접 고상반응법으로 K(+)-β/β"-Al2O3를 합성하여 상압하에서 소결하였다. 소결시 초기조성, 소결온도, 소결시간 및 성형첨가제가 β/β"-Al2O3의 고온상관계에 미치는 영향과 소결밀도에 대하여 분석하였고 미세구조의 변화를 연구하였다. 소결온도는 1650℃에서 1750℃까지 50℃ 간격으로 각각 30 min과 1 h 동안 유지하였다. 온도가 상승함에 따라 K2O의 증기압에 따른 potassium의 손실과 고온에서 β-Al2O3상의 상대적 안정성에 의하여 β" → β-Al2O3의 상전이가 진행되어 1750℃에서 β-Al2O3 상만이 존재하였다. 또한 소결밀도도 점차 증가하여 K1.67Mg0.67Al10.33O17(0.84K2O·0.67MgO·5.2Al2O3)의 조성을 가진 시편은 1750℃에서 1 h 동안 소결 후 이론밀도의 94%에 이르는 높은 소결밀도를 가졌다. 미세구조의 분석결과, 판상 및 침상의 β/β"-Al2O3 결정체는 소결온도가 상슴함에 따라 서서히 성장하다가 1700℃에서 액상의 형성과 함께 급격히 빠른 속도로 치밀화가 진행되어 1750℃에서 거대입자로 형성되었다.

K(+)-β/β"-Al2O3 was synthesized by direct solid state reaction in a ternary system K2O-MgO-Al2O3, and sintered at the atmospheric pressure. Influence of initial composition, sintering temperature, time, and forming additive to the high temperature phase relations, and the densification, as well as the change of microstructure were investigated. Sintering temperature was controlled from 1650 ℃ to 1750 ℃ at 50 ℃ intervals for 30 minutes and 1 h, respectively. Phase transformation of β"-Al2O3 to β-Al2O3 occurred gradually with temperature rising, and only β-Al2O3 existed at 1750 ℃. The highest sintered density of K(+)-β/β"-Al2O3 was about 94%, having the composition K1.67Mg0.67Al10.33O17(0.84K2O·0.67MgO·5.2Al2O3), and sintered at 1750 ℃ for 1 h. According to microstructure analysis, needle and plate shapes of β/β"-Al2O3 crystalline were gradually grown up to 1700 ℃. However, rapid densification with liquid phase was observed over 1700 ℃, and then large grain was formed at 1750 ℃.

Keywords:Solid electrolyte;K(+)-β/β"-Al2O3;Solid oxide fule cell;Ternary system K2O-MgO-Al2O3

[References]

Schaefer GW, Weppner W, Solid State Ion., 53, 559 (1992)
Schaefer GW, Aldinger F, cfi/Ber.DKG, 73, 109 (1996)
Kungang C, "Dense conductivity β”-Al2O3 ceramics by gel method", Ceramic Powders, ed. P. Vincenzini, 587 (1983)
Heavens SN, J. Mater. Sci., 19, 2223 (1984)
Youngblood GE, Miller GR, Gordon RS, J. Am. Ceram. Soc., 61, 86 (1978)
Jatkar AD, Culter IB, Gordon RS, Ceram. Microstructure, 76, 414 (1977)
Duncan JH, Barrow P, Brown PV, "Advanced ceramics in chemical process engineering", 231, Electroceramics (1988)
McEntire BJ, Miller ML, Gordon RS, Ceram. Bull., 63, 792 (1984)
Tan SR, May GJ, Ceram., 9, 103 (1977)
Jones IW, Miles LJ, Proc. Brit. Ceram. Soc., 99, 161 (1971)
Jatkar AD, Culter IB, Gordon RS, Ceram. Microstructure, 76, 414 (1977)
Schafer GW, Kim HJ, Aldinger F, Solid State Ion., 77, 234 (1995)
Vogel EM, Johnson DW, Yan MF, Ceram. Bull., 60, 494 (1981)
de Kroon AP, Schaefer GW, Aldinger F, Chem. Mater., 7, 878 (1995)
Song HI, Kim ES, Physica B, 150, 148 (1985)
Ham CH, Lim SK, Lee CK, Yoo SE, J. Korean Ind. Eng. Chem., 10(7), 1086 (1999)
Francis TL, Phelps FE, MacZura G, Ceram. Bull., 50, 615 (1971)
Whalen TJ, Tennehouse GJ, Meyer C, J. Am. Ceram. Soc., 57, 497 (1974)
Evan JRG, Stevens R, Br. Ceram. Trans. J., 83, 43 (1984)

[Referenced By]

[Related Articles]

[1] Schaefer GW, Weppner W, Solid State Ion., 53, 559 (1992)

[2] Schaefer GW, Aldinger F, cfi/Ber.DKG, 73, 109 (1996)

[3] Kungang C, "Dense conductivity β”-Al2O3 ceramics by gel method", Ceramic Powders, ed. P. Vincenzini, 587 (1983)

[4] Heavens SN, J. Mater. Sci., 19, 2223 (1984)

[5] Youngblood GE, Miller GR, Gordon RS, J. Am. Ceram. Soc., 61, 86 (1978)

[6] Jatkar AD, Culter IB, Gordon RS, Ceram. Microstructure, 76, 414 (1977)

[7] Duncan JH, Barrow P, Brown PV, "Advanced ceramics in chemical process engineering", 231, Electroceramics (1988)

[8] McEntire BJ, Miller ML, Gordon RS, Ceram. Bull., 63, 792 (1984)

[9] Tan SR, May GJ, Ceram., 9, 103 (1977)

[10] Jones IW, Miles LJ, Proc. Brit. Ceram. Soc., 99, 161 (1971)

[11] Jatkar AD, Culter IB, Gordon RS, Ceram. Microstructure, 76, 414 (1977)

[12] Schafer GW, Kim HJ, Aldinger F, Solid State Ion., 77, 234 (1995)

[13] Vogel EM, Johnson DW, Yan MF, Ceram. Bull., 60, 494 (1981)

[14] de Kroon AP, Schaefer GW, Aldinger F, Chem. Mater., 7, 878 (1995)

[15] Song HI, Kim ES, Physica B, 150, 148 (1985)

[16] Ham CH, Lim SK, Lee CK, Yoo SE, J. Korean Ind. Eng. Chem., 10(7), 1086 (1999)

[17] Francis TL, Phelps FE, MacZura G, Ceram. Bull., 50, 615 (1971)

[18] Whalen TJ, Tennehouse GJ, Meyer C, J. Am. Ceram. Soc., 57, 497 (1974)

[19] Evan JRG, Stevens R, Br. Ceram. Trans. J., 83, 43 (1984)