Effect of internal stress on physical temperature characteristics of Cerium-doped and Gadolinium-doded barium titanate ceramics

Abstract

The effect of internal stress on the physical properties (the temperature dependence of the dielectric constant and the lattice constant, and the diffuseness (gamma)) of solid solutions of 0.97BaTiO(3)-0.03Gd(2)O(3):1.5TiO(2) and 0.97BaTiO(3)-0.03CeO(2):1.5TiO(2) was investigated using various particle sizes of the starting BaTiO3, pressure-dielectric spectroscopy, and high-pressure X-ray analysis. The grain size was almost proportional to the particle size of the starting BaTiO3 and was inversely proportional to the internal stress. A sudden change in internal stress occurred at grain sizes of similar to 2 mu m for cerium-doped BaTiO3 and similar to 3 mu m for gadolinium-doped BaTiO3. With an increase in external pressure and a decrease in grain size, the lattice anomalies of the cubic-to-tetragonal transformation and two other factors (the tetragonal-to-orthorhombic and orthorhombic-to-rhombohedral transformations) shifted to lower and higher temperatures, respectively. The temperature dependencies of the dielectric constant and the lattice constant were less sensitive to external pressure in cerium-doped core-shell-grained BaTiO3 than in gadolinium-doped homogeneous-grained BaTiO3; this difference was attributable to internal stress, In cerium-doped BaTiO3, gamma was related to internal stress.