Optimization of Al-excess nonstoichiometry on the densification and plasma resistance of YAG ceramics

Abstract

The effects of Al-excess nonstoichiometry on the densification and plasma etching behavior of yttrium aluminum garnet (Y3Al5O12, YAG) were investigated. Al-excess composition driven by Al2O3 debris introduced during Al2O3 ball milling can promote the densification of YAG ceramics. This hypothesis was proved by using Al2O3 powder as an additive to YAG powder. It was verified that Al-excess nonstoichiometry designed by the addition of excess Al2O3 powder resulted in increased densification of YAG ceramics. At 1450 °C for sintering, the relative density of YAG ceramics increases from 98.58 % to 99.88 % with the addition of Al2O3 from 0 to 0.512 wt%. However, above 0.342 wt% concentration, Al2O3 was prepcipated in the YAG matrix, degrading the etching resistance. The optimum balance between the density and plasma etching resistance of YAG ceramics for application in a plasma environment was realized by adding 0.171 wt% of excess Al2O3. The density and surface roughness (Ra) of YAG ceramic after etching are 99.61 % and 17.6 nm, respectively.