Grain-boundary resistivity in barium titanate ceramic positive temperature coefficient sensors

Abstract

Several positive temperature coefficient resistors (PTCR's) are prepared using commercially available BaTiO/sub 3/ powders with different additives (Y, Mn, Nb, AST). We found that the different additives will result in different grain sizes, grain surface and porosity. However, the temperature-dependent resistivities of these samples do not have significant difference. A new model is proposed to explain this discrepancy and the three-segment characteristics in the PTCR.