One-step cold sintering process towards translucent BaF2 ceramics

BaF2 ceramics were prepared using a one-step cold sintering process with an ultra-low sintering temperature of 150 °C and uniaxial pressures ranging from 450 to 900 MPa. The relative density and microstructure improved steadily with the increasing pressure, and a fully densified microstructure with a relative density of 97.2% was achieved at 900 MPa. For BaF2 ceramics with a thickness of 1 mm, the optimum in-line transmittance in the visible light region (58.5%) was achieved at a wavelength of 720 nm, and the maximum value (65.3%) was obtained at 1864 nm. The permittivity of the ceramics increased gradually from 6.18 to 7.09 with increasing pressure, and the dielectric loss was optimized from 0.01 to 0.003. Additionally, the mechanical properties improved continuously with the increasing pressure, and the optimal compressive strength (257 MPa), hardness (2.01 GPa), and Young's modulus (54.8 GPa) were achieved when cold sintered at 900 MPa.