Transparent polycrystalline MgO ceramic fabricated by low-temperature vacuum sintering with MgF2 additive

This study introduces transparent MgO ceramics produced via simply vacuum sintering at 1200–1500 °C by optimal incorporation of MgF2 as a sintering additive. The effect of MgF2 content and sintering temperature on the densification process, optical, and thermal properties of MgO ceramics is presented with emphasis on its function as a sintering aid and adverse effect of MgF2 evaporation in the condition of high MgF2 content or high sintering temperature. MgO ceramic with 1.0 mol% MgF2 sintered at 1300 °C exhibits the highest relative density of 99.95% with average grain size of 17.46 μm. The in-line transmittance attains 60% at 1000 nm and >80% in the infrared range (3.8–6.8 μm), without absorption bands originated from the carbon contamination. The corresponding room-temperature thermal conductivity reaches 47.25 W/(m∙K). These results demonstrate that MgF2 is an outstanding sintering additive for the preparation transparent MgO ceramics.