Effect of acceptor (Mg) concentration on the electrical resistance at room and high (200 deg. C) temperatures of acceptor (Mg)-doped BaTiO{sub 3} ceramics

The behaviors of the electrical resistance at room and high (200 deg. C) temperatures of acceptor (Mg)-doped BaTiO{sub 3} ceramics with the increase of acceptor concentration were investigated. A series of coarse-grained specimens with different acceptor concentrations that were sintered at various oxygen partial pressures was prepared. The critical acceptor concentrations, beyond which the room temperature resistance increases abruptly, were experimentally evaluated and they were found to increase with a decrease in oxygen partial pressure during sintering. Each defect and electron concentrations at sintering and room temperature as a function of acceptor concentration were theoretically calculated. The results calculated could explain the experimentally observed behavior of the resistance versus acceptor concentration. The high (200 deg. C) temperature resistances under high electric field showed resistance degradation critically depending on acceptor concentration in the very small concentration range below {approx}0.1 mol %, which occurred easily with the increase of acceptor concentration. It was explained that such behavior was caused by the variation of potential barrier of grain boundaries for the migration of oxygen vacancies as a function of acceptor concentration.