Microstructure and dielectric properties in the La2O3-doped BaTiO3 system

Abstract

The effect of La2O3 addition on the crystalline phase, microstructure, and dielectric properties of BaTiO3 has been studied as a function of the amounts of La2O3. 0.3 mol% TiO2-excess BaTiO3 powder was synthesized by solid-state reaction, and then the powder compacts with various amounts of La2O3 were sintered at 1250 degrees C for 2 hours. Room temperature XRD showed changes in the lattice parameters and a decrease of tetragonality (c/a) as the amounts of La2O3 increased. It can be explained that the phase transition from tetragonal to cubic phase occurred because La3+ replaced Ba2+ site, which increased the instability of the tetragonal phase. As La2O3 was added over 0.1 mol%, the critical driving force for growth (Delta g(c)) increased over maximum driving force (Delta g(max)). As the result, the grain size decreased with La2O3 addition. Dielectric constant decreased as the amounts of La2O3 increased, which was analyzed with crystal structure and microstructure.