Grain size-dependent electrical properties of La1.95Sr0.05Zr2O7-δ as potential Proton Ceramic Fuel Cell electrolyte

The effect of grain size on the electrical properties of Sr-doped La2Zr2O7-δ ceramics densified by spark plasma sintering was studied by impedance spectroscopy. Structural and microstructural analyses were performed using X-ray and scanning electron microscopy techniques. Sets of samples with different grain sizes and relative densities have been obtained by playing on pressure or temperature during sintering. Depending on the grain size, different equivalent circuits are proposed and discussed. We show that varying the sintering conditions produces significant changes in the bulk and grain boundary conductivities, with a monotonic increase of the total conductivity with the increase of grain size. The Brick Layer Model (BLM) is used to explain the size and temperature dependencies of the total ionic conductivity of doped La2-xSrx Zr2O7-δ (x = 0.05).