(Pr, Co, Cr, La)-doped ZnO 바리스터의 전기적 특성에 미치는 소결온도효과

Abstract

The microstructure, electrical properties, and its stability of (Pr, Co, Cr, La)-doped ZnO varistors were investigated at different sintering temperatures in the range of <TEX>$1230{\sim}1300^{\circ}C$</TEX>. As the sintering temperature increased, the sintered density increased from 5.50 to <TEX>$5.77g/cm^3$</TEX>, the varistor voltage decreased from 777.9 to 108.0 V/mm, the nonlinear coefficient decreased from 77.0 to 7.1, and the leakage current increased from <TEX>$0.4{\mu}A\;to\;50.6{\mu}A$</TEX>. On the other hand, the donor concentration increased from <TEX>$0.90{\times}10^{18}\;to\;2.59{\times}10^{18}/cm^3$</TEX> and the barrier height decreased from 1.89 to 0.69 eV with increasing temperature. The stability of nonlinear electrical properties was obtained from sintering temperature of <TEX>$1260^{\circ}C$</TEX>. The varistors sintered at <TEX>$1260^{\circ}C$</TEX> marked the high electrical stability, with <TEX>$%{\Delta}V_{1mA}=+1.9%,\;%{\Delta}a=10.6%,\;and\;%{\Delta}I_L=+20%$</TEX> for DC accelerated aging stress state of <TEX>$0.95V_{1mA}/150^{\circ}C/24h$</TEX>.