Fabrication and ionic conductivity of apatite-type Mg doped lanthanum silicate films by DC plasma spraying

抄録

Dense films of Mg doped lanthanum silicate were deposited on Fe, stainless steel and lanthanum chromite substrates by atmospheric DC plasma spraying with an input energy of 44-21 kW. Scanning electron microscopic observation showed that microstructure of the films on these substrates consists of densely piled up particles with a disk-like shape. The film deposited with the lowest input energy of 21 kW includes a larger amount of smaller particles. Bulk ionic conduction was observed in the film deposited on lanthanum chromite substrates with an input energy of 38 kW and annealed at above 1073 K. On annealing at above 1173 K the ionic conductivity measured at 973 K rapidly increased up to 2 mS cm^-1, while the grain boundary resistance disappeared on annealing at above 1273 K and the electrode interface resistance gradually increased with the annealing temperature. A mixture of amorphous and apatite phase in the as-deposited films turned to a single apatite phase after the annealing at 1273 K.