Structure and conductivity investigations of alkaline earth substituted uranium oxide, U 1 − xM xO 2 ± δ (M = Mg, Ca, Sr) for solid oxide fuel cell applications

Abstract

Alkaline earth substituted UO 2 (U 1 − x M x O 2 ± δ ; M = Mg, Ca, Sr; 0.1 ≤ x ≤ 0.525) with fluorite structure was synthesized in reducing atmosphere. Structure and conductivity properties of U 1 − x M x O 2 ± 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 p O 2 > 10 − 4 atm and temperatures higher than 600 °C. The total conductivity measured for the best conducting U 1 − x M x O 2 ± δ material with M = Ca and x = 0.177 is as high as 3 S/cm at p O 2 < 10 − 4 atm at 600 °C. The relatively low ionic transference number ( t i∼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.