Silica-scavenging effect in zirconia electrolytes: Assessment of lanthanum silicate formation

Abstract

Yttria-stabilized zirconia (YSZ)-based composite electrolytes were produced by mixture and firing of the base electrolyte, namely with silica, and silica and lanthanum oxide, to study the impact of presence and formation of new phases on the electrical performance of the composite materials. Combined information obtained from structural, microstructural, and electrical characterization confirmed the formation of an apatite-type solid solution based on La 9.33Si6O26. The effectiveness of lanthanum oxide addition to remove silica by reaction was demonstrated. However, the conductivity of the composite electrolytes is lower than that of YSZ, probably due to lanthanum zirconate formation in-between the ceramic grains and/or relatively poor transport properties of the formed lanthanum silicate phase. The adopted procedure can be extended to other systems and combinations of properties based on predictable phase interactions.