Structure and conductivity investigations of alkaline earth substituted uranium oxide, U1 − xMxO2 ± δ (M = Mg, Ca, Sr) for solid oxide fuel cell applications

Alkaline earth substituted UO2 (U1 − xMxO2 ± δ; M = Mg, Ca, Sr; 0.1 ≤ x ≤ 0.525) with fluorite structure was synthesized in reducing atmosphere. Structure and conductivity properties of U1 − xMxO2 ± δ fluorites were investigated for possible application in solid oxide fuel cells (SOFC). At room temperature and ambient atmosphere the materials are stable; however they decompose at an oxygen partial pressure pO2 > 10− 4 atm and temperatures higher than 600 °C. The total conductivity measured for the best conducting U1 − xMxO2 ± δ material with M = Ca and x = 0.177 is as high as 3 S/cm at pO2 < 10− 4 atm at 600 °C. The relatively low ionic transference number (ti∼0.02) is disadvantageous for potential use as electrolyte material for SOFC applications. The high conductivity and possible depolarization effects suggest potential use as anode materials in SOFC.