Alumina ceramics are divided into two types: high-purity type and ordinary type.
High-purity alumina ceramics are ceramic materials with an Al2O3 content of more than 99.9%. Because their sintering temperature is as high as 1650-1990 ℃, and the transmission wavelength is 1 to 6 μm, they are generally made of molten glass to replace platinum crucibles; use its light transmission It can be used as a sodium lamp tube, and it can be used as an integrated circuit substrate and high-frequency insulating material in the electronics industry.
Ordinary alumina ceramics are classified into 99 porcelain, 95 porcelain, 90 porcelain, 85 porcelain and other varieties according to different Al2O3 content. Sometimes those with 80% or 75% Al2O3 content are also classified as ordinary alumina ceramic series. Among them, 99 alumina porcelain is used to make high temperature crucibles, refractory furnace tubes and special wear-resistant materials, such as ceramic bearings, ceramic seals and water valve discs; 95 alumina porcelain is mainly used as corrosion-resistant and wear-resistant parts; 85 porcelain Because it is often mixed with some talc to improve the electrical performance and mechanical strength, it can be sealed with metals such as molybdenum, niobium, and tantalum, and some are used as electrical vacuum devices.