Dh. Kim et al., INFLUENCE OF MICROSTRUCTURE AND GRAIN-BOUNDARY POTENTIAL BARRIER LAYER ON THE ELECTRICAL BREAKDOWN OF POSITIVE TEMPERATURE-COEFFICIENT BATIO3 CERAMICS, JPN J A P 1, 34(9A), 1995, pp. 4862-4869
The influence of the microstructure and the grain boundary potential b
arrier layer on the electrical breakdown of barium titanate positive t
emperature coefficient (PTC) ceramics was studied. Samples of various
grain sizes were prepared by adjusting the amount of Sb substitution i
nto Ba sites in barium titanate PTC ceramics. Samples exhibiting large
PTC effect (R(max)/R(min)) and fine grain size withstand high applied
voltage. It is clarified that grain size effect is related to the num
ber of grain boundaries per unit thickness of the samples because the
applied voltage drop is mainly across the potential barriers at grain
boundaries. However, the voltage dependence of a single grain boundary
potential barrier was more important in determining breakdown voltage
in our study. The voltage dependence of the grain boundary potential
barrier layer was due to the grain boundary built-in potential.