Investigations on structural and electrical properties of calcium substituted LSGM electrolyte materials for IT-SOFC

Strontium and magnesium doped lanthanum gallate, La0.9Sr0.1Ga0.8Mg0.2O2.85 (LSGM) and a few compositions of calcia (CaO) incorporated LSGM, La(0.9−x)CaxSr0.1Ga0.8Mg0.2O2.85; x≤0.10, were prepared by conventional solid state ceramic route. The X-ray diffraction patterns showed orthorhombic LSGM phase along with a few impure secondary phases. SEM micrograph depicted fairly dense grain morphology of the system. The textural properties were also found to be quite suitable for solid oxide fuel cell electrolyte applications. The electrical conductivity of the systems was measured in the frequency range 20 Hz to 1 MHz and temperature range 300–800 °C. The total conductivity of the system was found to first increase up to x=0.05 and thereafter it decreased for higher concentrations of the dopant. A small amount of calcia (upto x=0.05) scavenges the intergranular secondary impure phases resulting in a significant increase in grainboundary conduction. The presence of extra secondary phases in the higher compositions has been attributed to decrease in electrical conductivity.