The solid solution range of the La(Sr)Ga(Mg)O, perovskite was investigated and the oxygen ion conductivities of corresponding compositions were measured. The solubility of strontium could be extended by the addition of magnesium ions to establish a balance in the oxygen vacancies associated with A and B sites. In this way, the Sr limit in the solid solution was increased to more than 20% of the La content. Doping with either Sr or Mg enhanced oxygen ion conductivity, but whereas Sr doping yielded decreased activation energy with increasing concentration, Mg produced a higher activation energy with increased Mg content. La08Sr,,Ga,9Mg,,028, was found to have the highest conductivity apart from CeO,-based electrolytes at temperatures below 700°C, while La0 ,Sr,2Ga,,,Mg,150,,,, has the highest conductivity except for Bi20, at temperatures above 700°C. IntroductionThe most extensively studied electrolytes for solid oxide fuel cells have been based on Bi20,, CeO2, and Zr02 with the fluorite or related structure.'-4 In the search for new oxygen ion conductors, perovskites (ABO,) offer an interesting alternative because the structure is very tolerant of

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The electrical conductivity of SrTiO3 containing rare earth dopants (Y, La, Pr, Sm, Nd, Gd, or Yb) was measured at 600-900°C in reducing atmospheres. An unusually high conductivity was observed for the yttrium-doped samples compared to those with rare earth dopants, particularly at the composition of the solubility limit Sr0.88Y0.08TiO3−δ where the conductivity at 800°C was 64 S/cm. The conductivity was confirmed to be n-type by thermopower measurements. The oxygen deficiency was determined to be 1% by thermogravimetric analysis. Increasing the strontium vacancy concentration to Sr0.86Y0.08TiO3−δ effected a further improvement in conductivity to 82 S/cm. This material has high structural stability over a broad range of temperature (up to 1400°C) and oxygen partial pressure false(1­10−20 normalatmfalse). A simple defect model was developed to explain the change of electrical conductivity as a function of yttrium content and oxygen deficiency. © 2001 The Electrochemical Society. All rights reserved.

Binary oxide spinels composed of Mg, Al, Cr, Mn, Fe, Co, Ni, Cu, and Zn were synthesized. Electrical conductivity was measured in air at 500°–800°C. Thermal expansion was measured from room temperature to 1000°C. Ferrite spinels have thermal expansion coefficients of 11–12 ppm/K, compared with 7–9 ppm/K for other spinels except Cu–Mn and Co–Mn which show anomalous behavior. The highest electrical conductivity among transition metal spinels was found for MnCo2O4 (60 S/cm at 800°C) and Cu1.3Mn1.7O4 (225 S/cm at 750°C).

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