Fabrication, mechanical and optical performance of AM-gel casted YAG transparent ceramics

Abstract Aqueous gelcasting has been applied to form multiple advanced ceramics with large size or complex shape. However, the optical performance of transparent ceramics fabricated by gelcasting is not satisfactory due to the microstructure defects and residual organics. YAG ceramics with excellent optical transmittance were prepared through improving solid content of suspension, obtaining fine microstructure of fully dense ceramics without residual organics in this paper. The effects of ammonium citrate tribasic (TAC) and solid content on the rheological performance of suspension as well as the effect of solid content on the microstructure of green body were systematically investigated. The viscosity of suspension with 43 vol% solid content and 0.25 wt% TAC was as low as 0.03 Pa s at 100 s−1. The YAG ceramics (thickness 2.5 mm) with high optical transmittance (T = 83.2% at 1064 nm) were prepared from 43 vol% after vacuum sintering at 1780 °C for 8 h. The green body cast from 45 vol% solid content had an excellent bending strength about 29 MPa, and the residual pores were eliminated after vacuum sintering, while the residual organics was detected by optical microscopy and elemental analyzer inside YAG ceramics. The residual organics results in the decrease of in-line transmittance of YAG ceramic cast from 45 vol% solid content than that of ceramic cast from 43 vol%. This study suggests a promising prospect for AM gelling system in the cost-efficient manufacturing of highly transparent ceramics with high bending strength of green bodies.