Resistance degradation behavior of Ca-doped BaTiO3

Resistance degradation of Ca-doped BaTiO3 ceramics was investigated. A series of coarse and fine-grained (Ba1-xCax)TiO3 with only Ba site incorporation ranging x from 0 to 0.1, and Ba(Ti1-yCay)O-3 ceramics with only Ti site incorporation ranging y from 0 to 0.015, were prepared with similar grain sizes. The increase of x did not cause any distinct difference in degradation, whereas an increase in y caused a significant resistance degradation in both coarse and fine-grained specimens. The variation of ionic transference number (t(ion)) as evaluated by the Warburg impedance was negligible with increase in x, but significantly increased with the increase in y. These results demonstrate that the decrease of lattice parameters and lattice shrinkage by the Ba site incorporation of Ca has little influence on the resistance degradation, and that the oxygen vacancy concentration generated by the Ti site incorporation of acceptor Ca is a very important factor that governs resistance degradation.