Effect of phosphor doping on the microstructure and dielectric properties of barium titanate ceramics

The effect of phosphor doping on the sintering behaviour, microstructure and dielectric properties of BaTiO3 has been investigated. Diisopropyl phosphinate is added to high-purity BaTiO3 powder prepared by the wet chemical method with a final amount of 0.14 wt.% P2O5 with respect to the BaTiO3. Phosphor-doped BaTiO3 ceramics with a high density and uniform grain size have been produced by using wet processing and pressureless sintering without any binder. A scanning electron microscope, thermometric analysis, X-ray diffraction and an impedance analyser have been used to determine the microstructure as well as the dielectric properties. The phosphor cations can form a liquid phase belonging to the ternary system BaO-TiO2-P2O5, leading to the formation of BaTiO3 ceramics with high density at low temperature. Phosphor-doped BaTiO3 ceramics with a high density of 96% D-th are obtained by sintering at 1200 degrees C with a soaking time of 2 h. The dielectric constants of samples sintered at 1150 and 1200 degrees C are as high as 6100 and 5500, respectively; the Curie temperature of samples decreases with decreasing sintering temperature, Doping with a small amount of phosphor can improve the sintering and dielectric properties of BaTiO3 ceramics. (C) 1998 Elsevier Science S.A. All rights reserved.