Electrical properties of microwave-sintered (Sr0.4Pb0.6)TiO3 ceramics

The resistivity-temperature (rho-T) characteristics of the (Sr0.4Pb0.6)TiO3 materials prepared by a microwave sintering process were examined. The resistivities were significantly lowered by increasing the rate of cooling and were substantially increased by a heat-treatment process. The Curie temperature was not altered by a fast cooling process but was shifted from T-c = 302 degrees C to 210 degrees C when the as-sintered samples were post-heat-treated at 1200 degrees C for 1 h. The high Curie temperature of the as-sintered samples was proposed to be due to the core-shell structure of the grains. The ''shell'', which contained Pb-rich perovskite of the composition (Sr0.29Pb0.71)TiO3, was homogenized with core material during heat treatment. The variation in resistivity was ascribed to the modification of the concentration of cationic vacancies. The donor level (E(d)) and the deep trap level (E(t)) of the materials were, respectively, evaluated from the Arrhenius plot of rho-T characteristics at T < T-c and T > T-max regimes to be E(d) approximate to 0.078-0.193 eV and E(t) congruent to 1.66 eV + E(f), where E(f) is the Fermi level.