(INVITED)Effects of LiF sintering additive on the microstructure and mechanical properties of hot-pressed CaF2 transparent ceramics

CaF2 raw powders were synthesized by the chemical precipitation technique, and CaF2 ceramics with LiF sintering additives were fabricated by the hot-pressing (HP) sintering technique. The effects of LiF sintering additives on the optical transparency, microstructure and microhardness of CaF2 ceramics were investigated. The CaF2 ceramic with 0.05 wt% LiF exhibiting the best transparency, and the transmittance at 500 nm and 1800 nm are 71.5% and 87.8%, respectively. The average grain size of CaF2 ceramics increases with rising the amount of LiF from 0 to 1 wt%, while, the Vickers hardness (Hv) decreases. The average grain size, Hv, and fracture toughness (KIC) for the CaF2 ceramic with 0.05 wt% LiF are 85.6 ± 6.2 μm, 2.24 ± 0.06 GPa, and 0.11 ± 0.02 MPa m1/2, respectively.