Effect of Heat Treatments on the PTCR of <TEX>$BaTiO_3$</TEX> Ceramics Doped by <TEX>$Nb^{+5}$</TEX>

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J. Korean Ceram. Soc. > Volume 22(5); 1985 > Article

Journal of the Korean Ceramic Society 1985;22(5): 54.

$Nb^{+5}$ Doped $BaTiO_3$ 계에서 열처리가 PTCR 현상에 미치는 영향

문영우, 정형진, 윤상옥

한국과학기술원 무기재료연구실

Effect of Heat Treatments on the PTCR of $BaTiO_3$ Ceramics Doped by $Nb^{+5}$

ABSTRACT

This study is concerned with the mechanism of PTCR in $BaTiO_3$ ceramics doped by $Nb^{+5}$ Since the vacancy compensation layer at the grain boundary of n-type doped $BaTiO_3$ ceramics has been known as a major factor for surface state to give PTCR phenomena the dependence of PTCR on such vacancy compensation layer was attemped to be confirmed experimentally in this study. For the experiment quenching and annealing at various temperature after sintering were adopted to induce difference in the thickness of vacancycompensation layer so as to exihibit difference of PTCReffect eachother. The TEX>$Ba^{++}$ cocentration at the grain and grain boundary was measured by EDAX to confirm the formation of the vacancy compensation layer. It was found that i)either decrease in the temperature for quenching ii) or increase in the temperature for annealing improves the PTCR effect clearly iii)increase in TEX>$Ba^{++}$ concentration at the grain boundary results in the improvement of PTCR effect. It was concluded that all the experimental results gave the evidence for the dependence of PTCR effect on the vacancy compensation layer at the grain boundary which had been induced possibly by the $Ba^{++}$ diffusion by the heat treatment conducted.