Processing and Conductivity of Lanthanum Gallate

Abstract

The relationship between processing, structure and conductivity of lanthanum gallate was investigated. Powders of La0.8Sr0.2Ga1−yMgyO3-δ were synthesized by both solid oxide/carbonate reaction and citric acid/nitrate combustion processing. The latter method provided much finer and more homogeneous powders. The sintering of combustion synthesized powders, however, was more difficult. Accordingly, with the same sintering schedule the samples made from the combustion powder had lower density and lower conductivity than those made by routine ceramic processing. SEM micrographs showed that during sintering, the surfaces of LSGM samples sintered first, which left stranded porosity inside, particularly for samples made from the combustion powders. This difficulty could be overcome by two stage sintering and/or by isostatic pressing. By this technique, densities greater than 98% of theoretical were achieved. Conductivity was measured as a function of temperature and composition, and at 800°C, the maximum conductivity of 0.17 S cm−1 was obtained for the composition La0.8Sr0.2Ga0.875Mg0.125O1−δ.