Crystal and micro structures of plasma sprayed yttrium oxide coatings by axial injection of fine powder slurries

摘要

Yttrium oxide (Y_2O_3) coatings have been prepared with high power axial injection plasma spraying using fine powder slurries. It is clarified that the coatings have high hardness, low porosity and high erosion resistance against CF_4 contained plasma in the previous study. This suggests that the plasma spraying of Y_2O_3 with slurry injection techniques is applicable to fabricating equipments for semiconductor devices, such as dry etching. Surface morphologies of the slurry coatings with splats are almost similar to conventional plasma-sprayed Y_2O_3 coatings, identified from microstructural analysis by field emission SEM in this study. However, no lamellar structure has been seen from cross sectional analysis, which is apparently different from the conventional coatings. It has also been found that crystal structure of the slurry Y_2O_3 coatings mainly composed of metastable phase of monoclinic structure, whereas the powders and the conventional plasma spray coatings have stable phase of cubic structure. Mechanism of coating formation by plasma spraying with fine powder slurries will be discussed based on the findings.