Novel transparent LiF ceramics enabled by cold sintering at 150. C

Novel LiF transparent ceramics have been prepared using the cold sintering process at 150 degrees C combined with easily applied uniaxial pressures of 600-1050 MPa. The relative density and microstructure improve with the increasing uniaxial pressure, and fully densified LiF ceramics are obtained when cold sintered at 950-1050 MPa. The optimum optical property is achieved after cold sintering at 1050 MPa, where the maximum transmittance of 90.2% at 2.1 mu m is comparable to the LiF single crystal (similar to 95%). Meanwhile, excellent Vickers hardness (1.36 GPa) and compressive strength (382 MPa) are achieved after the cold sintering process, much higher than the conventional high-temperature sintered counterpart. Moreover, the optimal thermal conductivity (12.40 W/m.K) of the present LiF ceramics is higher than the typical fluoride ceramics such as CaF2 and comparable to the commercial LiF single crystal. Hence, this work opens up a novel, cost-effective and rapid fabrication route of transparent ceramics and paves the way to exploring novel transparent candidates.