Characterization of the Firing Schedule for Positive Temperature Coefficient of Resistance BaTiO 3

The development of positive temperature coefficient of resistance (PTCR) behavior during the firing procedure of semiconducting BaTiO 3 was characterized. The PTCR properties of BaTiO 3 were shown to be sensitive to the material's microstructure, liquid‐phase distribution, and extent of grain‐boundary oxidation. The PTCR behavior first became pronounced as the material cooled from the sintering stage at 1350°C to the annealing stage at 1175°C. Within this region, rapid oxidation of the grain boundaries occurred, which resulted in significant formation of charge carrier traps and a potential barrier. The rapid oxidation of the grain boundaries corresponded with the redistribution and solidification of the liquid phases. Once the carrier traps were established, the magnitude and slope of the PTCR jump increased during the annealing and cool‐down stages of the firing procedure because of further oxidation of the grain boundaries.