Systematic optimization of ball milling for highly transparent Yb:YAG ceramic using co-precipitated raw powders

Yb:YAG transparent ceramics were fabricated by vacuum sintering method using the co-precipitation synthesis of raw powders. These raw powders were mixed in ethanol doped with TEOS and ball milled for different time periods (0-20 h) and various solid contents of slurry (Sc = 7.8-38.5 wt%). The samples were vacuum sintered from 1350 °C to 1800 °C. Effects of ball-milling time and slurry concentrations on the morphology of powders, as well as densification, microstructure and transmittance of Yb:YAG ceramics were systematically evaluated. Results show that ball milling for 12 h can break the sintering neck of the particles and increase the optical transmittance to 81% at 1100 nm. For the Sc range of 38.5-20.3 wt%, decreasing slurry concentration improved the densification and in-line transmittance of Yb:YAG ceramics in the visible light region. When ball-milled for 12 h with 20.3 wt% slurry concentration, the Yb:YAG powders showed the most homogeneous particle distribution and highest densification rate, from which the ceramics prepared have the pore-free microstructure and the best transmittance. The highest optical transmittance of Yb:YAG ceramic sintered at 1750 °C for 15 h reaches up to 82% in the visible light region and 83.5% at 1100 nm, which is almost close to the theoretical transmittance.