Effect of Reoxidation Temperature on Electrophysical Properties of High-T_c Barium Titanate-Based PTCR Ceramics

摘要

Ceramic samples of (1-x)BaTiO_3-xNa_(0.5)Bi_(0.5)TiO_3 system were prepared by sintering in reducing atmosphere of N_2/H_2 and were subsequently reoxidized in air. The influence of reoxidation temperature firing on the PTCR effect of (1-x)BaTiO_3-xNa_(0.5)Bi_(0.5)TiO_3 ceramics was investigated. The effect of Na_(0.5)Bi_(0.5)TiO_3 concentration on resistivity and microstructure of the reoxidized samples was investigated by means of complex impedance spectroscopy and scanning electron microscopy. It has been found that the grain size decreases with the increase in Na_(0.5)Bi_(0.5)TiO_3 content. The values of minimum ρ_(min) and maximum ρ_(max) resistivities of the samples were observed to increase with the increase in reoxidation temperature in the 600 - 1000°C temperature range. It was shown that with increasing in reoxidation temperature of (1-x)BaTiO_3-xNa_(0.5)Bi_(0.5)TiO_3 solid solutions, potential barrier at grain boundaries increases.