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

Ionic conduction behaviors in aluminum containing oxides, Lan-xSr1+xAlnO3n+1-alpha (n=1 and 2), and in lanthanum niobate-based oxides, La3-xSrxNbO7-alpha, were investigated using electrochemical methods at elevated temperatures. In La1-xSr1+xAlO4-alpha, single-phase was confirmed at 0less than or equal toxless than or equal to0.10. The highest conductivity in this solution appeared when x=0.10 (2.4 x 10(-4) S cm(-1) at 1000 degreesC in H-2). 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. Protonic conduction was confirmed in La3-xSrxNbO7-alpha. The highest conductivity appeared at x=0.4 (1 x 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. (C) 2002 Elsevier Science B.V. All rights reserved.