The Effects of SiO2 Addition and Cooling Rate Change by Sol-gel Processing in Semiconducting BaTiO3 Ceramics

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J. Korean Ceram. Soc. > Volume 33(12); 1996 > Article

Journal of the Korean Ceramic Society 1996;33(12): 1301.

반도성 $BaTiO_3$ 세라믹스의 Sol-gel법에 의한 $SiO_2$ 첨가 및 냉각속도 효과

권오성, 정용선¹, 윤영호², 이병하

명지대학교 공과대학 무기재료공학과
¹한양대학교 세라믹소재연구소
²삼화콘덴서 공업(주)

The Effects of SiO2 Addition and Cooling Rate Change by Sol-gel Processing in Semiconducting BaTiO3 Ceramics

ABSTRACT

Generally it requires high sintering temperatures more than 135$0^{circ}C$ to make semiconductive BaTiO3 ceramics. Also it is very difficult to achieve a homogeneous mixing in solid-state reaction method. Therefore the liquid phase distributed to non-uniform dilute the characteristics of PTCR. In order to improve the uniformity this study is used the sol-gel coating method. Using this method we studied the new manufacturing process that had a high reproducibility and mass production capability. Tetraethyl orthosilicate (TEOS) was used as a source of Si. The semiconductive BaTiO3 ceramics which was produced by sol-gel method for the SiO2 addition and sintered between 124$0^{circ}C$ and 130$0^{circ}C$ showed almost same resistivity at room temperature among 125$0^{circ}C$ and 130$0^{circ}C$. As the results We could be sintered the semiconducting BaTiO3 ceramics at lower temperature even at 125$0^{circ}C$ maintaining the same specific resistivity ratio ($rho$max/$rho$min) at 130$0^{circ}C$. The specific resistivity both below and above the Curie temperature were increased by slow cooling and the steepness of the plots in the reasion of transition from low to high resistance increased as the cooling rate decreased.

Key words: $BaTiO_3$, PTCR, Sol-gel coating method, etraethyl orthosilicate(TEOS), Thermistor