Synthesis and Property Study of Multi-Doped LaGaO<sub>3</sub> for SOFC Application

Abstract

. La0.8Sr0.2Ga0.8Mg0.2O2.8 (LSGM) acts as a promising electrolyte material for solid oxide fuel cell (SOFC) at intermediate temperature although its single phase synthesis is comparably difficult. However, phase purity is influenced by the amount and type of the transition metals doped and with the addition of transition metals both bulk and grain boundary conductivities are increased. In this work, Co is doped at Ga site of LSGM by Pechini method. The powders are then calcined, sintered and subsequently characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermo-mechanical (TMA), nanoindentation test and impedance analysis. As observed from XRD single phase La0.8Sr0.2Ga0.8Mg0.15 Co0.05O2.8 (LSGMC) is found at 1400°C and getting its single phase is easier than synthesizing single phase LSGM. As found from Rietveld analysis, the synthesized LSGMC is having orthorhombic crystal structure with Pbnm space group. TEM images show the spherical particles with size ~35 nm. Density of the sintered pellet as measured by Archimedes principle is found to be 98% at 1400°C, 8h. Thermal expansion co-efficient of the sintered pellet is found to be 12.2 ×10-6/°C, which is nearly same as of LSGM and nearly matches with other SOFC components. Hardness and Youngs modulus of the material as found from the Nanoindentation test are found as 13.14 ±0.9 GPa and 204.5±5.7 GPa respectively, which are suitable for SOFC application. The diffused semicircle observed in Nyquist plot simulated as (RQ)(RQ) circuit and the ionic conductivity is found to be higher than LSGM at equivalent temperature.