Managing particle contact characteristics in powder mixtures with bimodal size distribution towards improved transparency for Yb:YSAG ceramics

Ball-milled powder mixtures for solid-state reactive sintering may exhibit distinct particle size distributions due to varying properties of raw powders. This work reports the ball-milled powders for 5 at% Yb: Y₃Sc_0.1Al_4.9O₁₂ transparent ceramics with bimodal particle size distribution, and the corresponding calcining process to effectively improve their densification ability. With increasing calcination temperature up to 1000°C, the specific surface area and small-large particle contact fraction increase, which decreases when over 1000°C. The enhanced particle rearrangement capability at 1000°C leads to minimum pore existence in ceramics after pressureless sintering at 1780°C under vacuum. This results in a nearly theoretical transmittance of 84.7 % at 1100 nm and 84.0 % at 400 nm, respectively. The evolution of particle contact characteristics is governed by distinct interdiffusion rates between smaller Y₂O₃ particles and larger Al₂O₃ particles before 1000°C, and Oswald ripening after there’s no phase distinction between different-sized particles.