Grain-boundary surface states of (Ba,Pb)TiO3 positive temperature coefficient ceramics doped with different additives and its influence on electrical properties

The electrical performance of (Ba,Pb,La)TiO3 ceramics doped with different additives and exhibiting a positive temperature coefficient of resistance (PTCR) behavior was investigated. Specifically, three PTCR equations based on the Heywang-Jonker model were used to correlate measurements and calculations of resistivity. The good agreement was attributed to the assumption that different additives lead to different surface states such as cation vacancies, acceptor impurities and interface states from oxygen adsorption are found at the grain boundary.