Electrophysical and thermomechanical properties of perovskites La0.5A0.5Mn0.5Ti0.5O3–δ (A = Ca, Sr, Ba) used as fuel cell anodes: the effect of radius of alkali-earth cation

Resumo

The effect of the radius of the alkali-earth cation substituted into the A sublattice of La_0.5A_0.5Mn_0.5Ti_0.5O_3–δ (А = Са, Sr, Ba) perovskites on their stability and transport and thermomechanical properties is considered. The increase in the cation radius is shown to improve the phase stability and decrease the conductivity under both oxidative and reductive conditions. The thermal and chemical expansion of La_0.5A_0.5Mn_0.5Ti_0.5O_3–δ ceramics is studied by dilatometry in controlled atmospheres and a wide temperature range at p(O₂)=10^–21–0.21 atm. The coefficients of thermal expansion of La_0.5A_0.5Mn_0.5Ti_0.5O_3–δ are in the interval of (10.7–14.3)× 10^–6 K^–1, i.e., compatible with those of standard solid electrolytes of solid-oxide fuel cells. The maximum chemical expansion does not exceed 0.2% at isothermal reduction in the CO‒CO₂ mixture.