Gemstone
The hardest oxide crystal, sapphire maintains its high strength at high temperatures, with good thermal performance and excellent transparency. It has a 1.5 μ M to 6.0 μ High transmittance of m. On the other hand, it has chemical resistance to ordinary acids and bases up to 1000 ° C and HF below 300 ° C. These characteristics encourage its widespread use in harsh environments that require light transmission from vacuum ultraviolet to near-infrared range.