Alumina ceramics are divided into two kinds of high purity and common type. High purity alumina ceramics Al2O3 content in more than 99.9% of the ceramic materials, due to the sintering temperature as high as 1650 - 1990 DEG C, the transmission wavelength is 1 ~ 6 m, usually made of molten glass to replace platinum crucible: the transparency and can be alkali metal corrosion as sodium lamp; in electric industry sub available for integrated circuit substrates with high frequency insulating materials. Ordinary alumina ceramics by Al2O3 content is divided into 99 different types, 95 porcelain, 90 porcelain, 85 porcelain and other varieties, sometimes Al2O3 content in 80% or 75% are also classified as ordinary alumina ceramic series. Which 99% alumina ceramic material for making high temperature crucible, refractory furnace tube and special wear-resistant materials, such as ceramic bearings, ceramic sealing parts and valve piece and so on; of 95 alumina ceramics is mainly used for the corrosion resistance, wear parts; 85 alumina ceramics since it is often mixed with some talcum and improve the electrical properties and mechanical strength, and molybdenum, niobium, tantalum metal sealing connection, and some used as electric vacuum device.