Microstructures of La₂Ce₂O₇ coatings produced by plasma spray-physical vapor deposition

La₂Ce₂O₇ (LC) coatings were produced by plasma spray-physical vapor deposition (PS-PVD). To achieve the quasi-columnar microstructure, three spray parameters with different net power, spray distance, and carrier gas flow rate were applied. The relationships between the spray parameters and the microstructures were investigated. It was found that the coatings’ microstructure is more sensitive to the net power and carrier gas flow rate rather than the spray distance. The corresponding phase and chemical compositions of coatings were studied by X-ray diffraction (XRD) and energy dispersive spectrometer (EDS), respectively. The results indicate that the lattice parameters of LC phases have positive correlations with average atomic La/Ce ratios of the coatings. The regional characteristics of the optimized coating were investigated by transmission electron microscope (TEM). Super-lattice diffraction patterns of TEM revealed that the coating is pyrochlore phase. “Particle-interruption” mechanisms in the quasi-columnar coating were proposed and discussed.