Synthesis of porous (Ba,Sr)TiO3 ceramics and PTCR characteristics

Porous (Ba,Sr)TiO3 ceramics are synthesized by the addition of partially oxidized Ti powder, corn- or potato-starch into the (Ba,Sr)TiO3 powder. It is found that the porosity and pore size increased and the grain size decreased with increasing the additive. All the samples with and without the additive at room temperature exhibit the tetragonal structure. Positive temperature coefficient of resistivity (PTCR) jump of the samples with the additive is 1–2 orders higher than that of sample without the additive. The complex impedance results indicate that the development of PTCR characteristic in the porous (Ba,Sr)TiO3 ceramics containing additive is related to grain boundaries, which basically equals to that in ordinary BaTiO3 without additive.