Preparation of dense silicate electrolyte coating with low pressure plasma spraying and very low pressure plasma spraying for intermediate-temperature solid oxide fuel cells

Magnesium doped lanthanum silicate with apatite-type structure, as a solid electrolyte for IT-SOFC (intermediate-temperature solid oxide fuel cells), was prepared by solid state sintering. The electrolyte coatings were fabricated by LPPS (Low Pressure Plasma Spraying) and VLPPS (Very Low Pressure Plasma Spraying). Their microstructures and phase composition were characterized by SEM and XRD. The gas permeability of coatings was measured with pure H ₂ and O ₂ at room temperature. It is shown that dense lanthanum silicate coatings can be obtained by LPPS and VLPPS. Amorphous and trace phases existed in coating deposited by LPPS. Well-crystallized lanthanum silicate coating can be prepared by one step VLPPS. The specific permeability of coating fabricated by VLPPS is 1.79 × 10 ^-19 m ².