Alumina ceramics are currently classified into two types, high-purity and normal-type. High-purity alumina ceramics ceramic materials with a content of 99.9% or more of Al2O3 have a sintering temperature as high as 1650-1990°C and a transmission wavelength of 1 to 6 μm. They are generally made of molten glass to replace platinum crucibles: Alkaline and corrosive alkali metals can be used as sodium lamps; it can be used as an integrated circuit substrate and high-frequency insulation material in the electronics industry. Ordinary type alumina ceramics are divided into 99 porcelains, 95 porcelains, 90 porcelains, 85 porcelains, etc. according to the content of Al2O3. Sometimes the content of Al2O3 is 80% or 75%, which is also classified as ordinary alumina ceramics. Among them, 99 alumina ceramic materials are used to make high-temperature crucibles, refractory furnace tubes and special wear-resistant materials, such as ceramic bearings, ceramic seals, and water valve plates; 95 alumina ceramics are mainly used as corrosion-resistant and wear-resistant components; 85 porcelain As part of the talc is often incorporated, the electrical properties and mechanical strength are improved, and it can be sealed with molybdenum, tantalum, niobium, and other metals, and some are used as electrical vacuum devices.