Influence of Sintering Strategy on the Characteristics of Sol-Gel Ba_{1- x}Ce _x Ti_{1- x/4}O₃ Ceramics

Single-phase Ce³⁺-doped BaTiO₃ powders described by the nominal formula Ba_1-xCe_xTi_1-x/4O₃ with x = 0.005 and 0.05 were synthesized by the acetate variant of the sol-gel method. The structural parameters, particle size, and morphology are strongly dependent on the Ce³⁺ content. From these powders, dense ceramics were prepared by conventional sintering at 1300 °C for 2 h, as well as by spark plasma sintering at 1050 °C for 2 min. For the conventionally sintered ceramics, the XRD data and the dielectric and hysteresis measurements reveal that at room temperature, the specimen with low cerium content (x = 0.005) was in the ferroelectric state, while the samples with significantly higher Ce³⁺ concentration (x = 0.05) were found to be in the proximity of the ferroelectric-paraelectric phase transition. The sample with low solute content after spark plasma sintering exhibited insulating behavior, with significantly higher values of relative permittivity and dielectric losses over the entire investigated temperature range relative to the conventionally sintered sample of similar composition. The spark-plasma-sintered Ce-BaTiO₃ specimen with high solute content (x = 0.05) showed a fine-grained microstructure and an almost temperature-independent colossal dielectric constant which originated from very high interfacial polarization.