Effect of heat treatment temperature on performance of plasma-sprayed apatite-lanthanum silicate coatings as electrolytes for IT-SOFC

Magnesium-doped lanthanum silicate with apatite-type structure was prepared by solid state sintering, as a solid electrolyte for intermediate temperature solid oxide fuel cells. The electrolyte layers were fabricated by air plasma spraying, followed by post heat treatments, and their microstructures and phase composition were characterized by SEM and XRD. The gas permeation of electrolyte layers was measured by a specific instrument with pure H₂ and O ₂ at room temperature. It is shown that amorphous and trace phases exist in as-sprayed electrolyte layer, and then disappear after a post heat treatment in air furnace at temperature up to 1000 C. The permeability can be decreased by the heat treatment, especially after 4 h at 1000 C.