Effects of artificial pores and purity on the erosion behaviors of polycrystalline Al2O3 ceramics under fluorine plasma

Abstract

Microstructure developments under fluorine plasma have been investigated in the Al2O3 ceramics containing artificial pores with controlled purity. The erosion behaviors by fluorine plasma consisted of a uniform erosion throughout the specimen surface and local erosions around the artificial pores and defects such as intrinsic irregular pores and damages formed during the grinding and polishing steps. The effects of the pores on the microstructure development were more distinct in the low purity Al2O3 specimen. The erosions around the pores, in the beginning, showed polygonal or flower-like microstructures in high or low purity Al2O3, respectively, indicating a weak grain boundary of glassy phase under the fluorine plasma. The extended plasma treatment resulted in loose structures around the pores in the low purity specimen, possibly producing contamination particles. In contrast to the polycrystalline Al2O3, single crystalline Al2O3 showed only uniform erosion. Although the microstructure developments were completely different depending on purity, porosity and polycrystallinity, etch depths did not appear so different, implying that the etch depths might not properly represent the plasma resistance of the materials.