Combustion synthesis and characterization of Sr and Ga doped LaFeO3

Abstract

A homogeneous perovskite oxide La0.5Sr0.5Ga0.2Fe0.8O3−δ (LSGFO) has been synthesized by self-propagating high-temperature synthesis (SHS). The homogeneity and the particle size of the combustion product may be increased by decreasing the cooling rate of the sample, either by increasing the sample diameter or by controlling the post-combustion temperature. The particle morphology depends on the gaseous and molten compounds formed as the combustion front passes through the sample. The perovskite oxide maintained its cubic structure at all temperatures in air. However, a decomposition of LSGFO occurred at 860°C under a simulated syngas environment (22% CH4+57% H2+21% CO2, oxygen partial pressure of about 10−17 atm). The maximum electrical conductivity of a disc prepared from the SHS powder was 142 S/cm at 580°C under oxygen pressure of 1 atm. The LSGFO may be suitable for use as a membrane in syngas production since its thermal expansion in air and reducing environment are rather close at high temperature.