Suppression of carbon contamination in SPSed CaF2 transparent ceramics by Mo foil

Transparent calcium fluoride (CaF2) ceramics were fabricated by spark plasma sintering (SPS) using Mo foil to separate from graphite die, and the effect of Mo foil on transparency, microstructure and carbon contamination was investigated. The discoloration was removed and the transmittance increased from 8% to 54% at the wavelength of 300 nm and 63% to 86% at 1100 nm by using Mo foil. The average grain size of CaF2 ceramics SPSed at 1100 °C was 16 μm by using graphite sheet, whereas it was 260 μm by using Mo foil, indicating that ceramics with large grain size are possible to reach high transmittance. Raman spectroscopy and X-ray photoelectron spectroscopy revealed that carbon contamination in the CaF2 ceramics using Mo foil decreased 78% than that shielded by graphite sheet.