Influences of nanometer inhomogeneity on the phase transition & PTC effectin doped BaTiO3 ferroelectric ceramics

The nanometer (nm) inhomogeneity caused by the incorporation of Curie tempe rature shifters, for example, Pb2+ or Sr ions, is being suggested to occur in the BaTiO3 ferroelectric ceramics. This will result in the phase transit ion being diffused into a region called Curie temperature region, and the t ransition temperature should be expressed by an average Curie temperature. The relationships of average Curie temperature with the doping amount of sh ifting ions are: 120+400x degrees C (x less than or equal to 0.5), for (Pbx Ba1-x)TiO3 (PBT); and 120-(2200/7)x degrees C (x less than or equal to 0.7) for (SrxBa1-x)TiO3 (SBT). Furthermore, the nanometer inhomogeneity brings about the diffusing of phase transition and the lowering of both the jump t emperature and the positive temperature coefficient (PTC). The enveloping f unctions of extreme value of resistivity are obtained. The influences are e stimated through numerical calculation. Finally, the phenomenon encountered by Kuwabara et al. and the series curves obtained by Andrich, are explaine d.