The oxide ion conductivity in doped perovskite-type materials was investigated. It was found that, among the alkaline earth cations, the addition of Ca at Nd sites was effective in increasing the oxide ion conductivity. The latter increased anomalously with increasing amount of Ca, and attained its maximum in Nd0.9Ca0.1AlO3; which seemed to correspond to the maximum solid solubility of Ca at Nd sites. The addition of cations at Al sites in Nd0.9Ca0.1AlO3 was also effective in increasing the oxide ion conductivity. It was found that the substitution of Ga at Al sites was effective in enhancing the oxide ion conductivity of Nd0.9Ca0.1AlO3. The oxide ion conductivity increased with increasing Ga content, and the highest oxide ion conductivity was exhibited by Nd0.9Ca0.1Al0.5Ga0.5O3. Since the increased O ion conductivity which was caused by doping with Ga suppressed p-type semiconduction under high O partial pressures, the electrical conductivity was almost independent of the O partial pressure. The results suggested that the perovskite-type oxide, Nd0.9Ca0.1Al0.5Ga0.5O3, exhibited almost purely oxide ion conductivity and high electrical conductivity over wide ranges of O partial pressure and temperature.

T.Ishihara, H.Matsuda, Y.Takita: Journal of the Electrochemical Society, 1994, 141[12], 3444-9