High-Temperature Properties of Layered Oxides (La,Tb,Sr)2CuO4 ± δ with T*-Structure

−The high-temperature thermal expansion and electrical conductivity of the T*-phase cuprates La1.2 – xSrxTb0.8CuO4 ± δ (x = 0, 0.05) were studied for the first time with the goal to evaluate their applicability as cathode materials for solid-oxide fuel cells. According to dilatometry data, the thermal expansion coefficients (TECs) of the oxides in air in the temperature range of 303–1123 K were 12.2 (x = 0) and 12.7 ppm K–1 (x = 0.05). A study of high-temperature crystal structure of La1.2Tb0.8CuO4 ± δ revealed anisotropy of TEC along crystallographic axes (TEC(c)/TEC(a) = 1.35). Analysis of high-temperature electrical conductivity of the cuprates at various oxygen partial pressures showed that holes are the main charge carriers. The conductivity at 973 K in air was 0.3–0.6 S/cm. A possible reason for relatively low conductivity is the formation of Tb4+ cations at high temperature, which act as traps for main charge carriers. The results of this study indicate that La1.2 – xSrxTb0.8CuO4 ± δ may have only limited applicability as the cathode material in SOFC, for example, as thin film functional coatings.