Protonic Conduction in LaPO₄-based Ceramics

Abstract

Significant protonic conduction has been found at high temperature in LaPO₄-based ceramics, in which protons are considered to dissolve as defects in the presence of hydrogen-containing gases. This report describes electrolyte properties of 5mol% Sr-substituted LaPO₄. In air, this material can be regarded as a pure protonic conductor at 600°C when P_H2O>1kPa, and at 700°C when P_H2O> 3kPa. At high temperature, low P_H2O, and high P_O2, the material shows mixed conduction by protons and electron holes. The contribution of electron hole conduction to the total conductivity becomes significant as temperature increases, P_O2 increases, and P_H2O decreases, although protonic conduction is still dominant even at 900°C in wet air.