Effect of citric acid on the microstructure and optical properties of transparent YAG ceramics by reactive-SPS

Commercial α-Al2O3 and Y2O3 powders with 0.5 wt% TEOS were used to fabricate transparent polycrystalline YAG ceramics by reactive spark plasma sintering. The powder mixtures were dispersed with dispersants of PAA and citric acid in aqueous slurry. YAG specimens sintered at 1400 °C for 3 min were used to investigate the effect of processing parameters on the microstructure and the optical properties. It is found that a pretreatment of the powders mixture with 0.6 wt% citric acid can significantly improve the microstructure homogeneity of the as-sintered YAG ceramics. After post-annealing in wet air, the specimen sintered from the treated powders mixture was transparent, while the specimen from the untreated powders mixture was hazy. The effects of citric acid for this were investigated in this paper.