Optical MgO Ceramics Fabricated by Hot Pressing with LiF

Abstract

This study presents the results of an investigation into the hot pressing of optical magnesium oxide (MgO) ceramics from powders synthesized via the self-propagating high-temperature synthesis (SHS) method. A preprocessing technique for industrially produced raw materials is proposed to adjust their impurity composition to a level sufficient for obtaining high-quality optical ceramics. The addition of 1 wt % LiF as a sintering aid to the SHS precursor enables the fabrication of MgO ceramics with a thickness of 1.5 mm, achieving near-theoretical transmittance across the material’s transparency range (0.2–9.5 µm). It is demonstrated that even a small amount of LiF (as low as 0.125 wt %) significantly enhances the transparency of the ceramics; however, it also leads to a substantial reduction in thermal conductivity within the studied temperature range (25–300°C). The thermal conductivity of MgO ceramics without the sintering aid is measured at 67.7 W/(m K) at room temperature. The microhardness of the fabricated ceramic samples remains largely unaffected by the LiF content in the precursor, with values ranging from 9 to 11 GPa.