Influence of Rare Earths on Electric Properties and Microstructure of Barium Titanate Ceramics

The influence of rare earths on electrical resistivity and microstructure of barium titanate ceramics doped with rare earth ions Y, Dy, Ho, Er and Y at the concentrations of x = 0.001 × 0.01 was investigated by the means of X-ray diffraction, scanning electron microscopy and electric properties testing. The results showed that a dramatic decrease in resistivity occurred at the concentration of 0.3% of La-doped sample. However, the range of concentration for semiconducting samples doped with Dy, Ho, Er and Y was wider, especially for Y-doping. The experimental results indicated that below the critical concentration of Dy, Ho, Er and Y, the substitution took place in the barium sublattice with electronic compensation, above the critical concentration, gradually the rare earth ions began to substitute for titanium. As for Hodoped BaTiO3 ceramic, the resistivity jump (PTCR effect) near the Curie temperature was the highest in case of lower dopant concentration of 0.3%. Fine-grained structure of sample doped with 0.6% Dy led to the increasing of breakdown electric field strength and dielectric constant of ceramic samples. In contrast, coarsed-grained structure of sample doped with 0.3% Dy showed semiconducting property.