Protonic conduction in lanthanum strontium aluminate and lanthanum niobate-based oxides at elevated temperatures

Ionic conduction behaviors in aluminum containing oxides, Lan−xSr1+xAlnO3n+1−α (n=1 and 2), and in lanthanum niobate-based oxides, La3−xSrxNbO7−α, were investigated using electrochemical methods at elevated temperatures. −xSr1+xAlO4−α, single-phase was confirmed at 0≤x≤0.10. The highest conductivity in this solution appeared when x=0.10 (2.4×10−4S cm−1 at 1000 °C in H2). Electromotive forces (emfs) of gas concentration cells and H/D isotope effect on conductivity suggested the certain contribution of protons to conduction. In hydrogen, pure ionic conduction in La2SrAl2O7 was suggested. ic conduction was confirmed in La3−xSrxNbO7−α. The highest conductivity appeared at x=0.4 (1×10−3 S cm−1). Emfs of water vapor concentration cell in air suggested the existence of protonic conduction under high oxygen partial pressure condition.