Ceramic samples were prepared by means of the high-temperature solid-state reaction of oxides and carbonates. Distorted ABO3-type structures, which were classified as belonging to the orthorhombic system, were obtained. These were A-site sub-stoichiometric and/or B-site Dy-doped materials. It was found that the conductivity of Sr(Zr1-xDyx)O3 was slightly lower than that found for Y-doped strontium zirconate with an identical trivalent dopant content. It increased with water-vapor pressure, as expected for proton-conducting materials. In the case of Dy-free perovskites with a slight A-site sub-stoichiometry, Sr1-xZrO3 (where x was less than 0.02), the conductivity decreased by a few orders of magnitude and was almost independent of the water-vapor pressure. The corresponding B-site doped materials, Sr1-y(Zr1-xDyx)O3, had the highest conductivities; which again depended upon the water-vapor pressure. It was suggested that this indicated that B-site doping was essential in order to obtain significant proton conductivity. The behavior of these materials could be explained in terms of classical defect chemistry, if it were assumed that the electron hole mobilities at about 300C were smaller than that of protons. This trend was reversed at temperatures above 500C. In highly sub-stoichiometric perovskites, with y greater than 5, the conductivity was minimal (even for B-site doping) and was independent of the water-vapor pressure. A blocking inter-grain phase was believed to control the electrical transport properties.

B.Gharbage, F.M.B.Marques, J.R.Frade: Journal of the European Ceramic Society, 1996, 16[11], 1149-56