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

Abstract

Novel LiF transparent ceramics have been prepared using the cold sintering process at 150 °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 µm is comparable to the LiF single crystal (∼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.