$BaTiO_{3}$ PTC 서미스터를 제조하여 그 전기적 특성을 조사하였다. PTC 서미스터의 저항률은 $20^{circ}C$에서 $200^{circ}C$까지 $20^{circ}C$ 간격으로 측정되었다. 이 시편의 ac 복소 임피던스 분석을 통하여 PTC 서미스터의 입계저항, 입계정전용량, bulk 저항 등을 조사하였다. 전자현미경을 사용하여 grain을 확인하고 평균 입경을 구하였으며 측정된 평균 입경은 $3.8{mu}m$에서 $8.8{mu}m$까지 되었다. 평균 입경은 소결온도가 높을수록 커지는 경향을 보였으며 최대저항률 증가비는 $4{ imes}10^{5}$ 정도였다. Bulk 저항률은 소결온도가 $1340^{circ}C$ 이상일 경우는 측정온도가 증가함에 따라 감소하였다. 측정온도가 증가할수록 입계저항은 n의 지수함수적으로 증가하였으며, 입계정전용량은 감소하고, 입계의 전위 장벽은 증가하였다. 입계전하밀도는 측정온도가 올라갈수록 증가하였으나, 측정온도가 약 $110^{circ}C$ 이상일 경우 더 이상 증가하지 않았다.
PTC thermistor has been fabricated with as-received $BaTiO_{3}$ powder and its electrical properties were investigated. The resistivity of the PTC thermistor was measured at $20^{circ}C$ intervals from $20^{circ}C$ to $200^{circ}C$. The electrical characteristics of the PTC thermistor are determined by the ac complex impedance analysis. The average grain size measured with a scanning electron microscope increased from $3.8{mu}m$ to $8.8{mu}m$ with increasing sintering temperature between $1280^{circ}C$ and $1400^{circ}C$. The maximum resistivity jump was $4{ imes}10^{5}$. The bulk resistivity of the thermistor sintered above $1340^{circ}C$ decreased with increasing temperature of the measurement. The grain boundary resistance increased exponentially, the grain boundary capacitance decreased, and the built-in potential at the grain boundary increased with increasing temperature of the measurement. The charge densiy at the grain boundary increased with increasing temperature up to $110^{circ}C$, which leveled off with further increase in measuring temperature.
