Causes of discoloration of alumina ceramics after sintering

Alumina ceramics are made by using alumina as the main raw material, adding 6-30% of clay, magnesium oxide, calcium oxide, titanium oxide and other sintering accelerators, and sintering at 1450-1800 ℃ after mixing. The more alumina content, the better the inherent properties of alumina can be exerted, and the better the performance, but it becomes difficult to manufacture as the alumina content increases. The characteristics of alumina porcelain are that it still has good insulating properties at high temperature.

Pure alumina porcelain can be used at a temperature of 800 ° C. Its mechanical strength is the highest among all oxide ceramics, and its thermal conductivity is large and thermal shock resistance. Strong, can be used to manufacture spark plug insulators, insulating parts of ultra-high-frequency high-power electric vacuum devices, electronic tubes and rectifier shells, integrated circuit substrates, etc.

Alumina ceramic structural parts are mainly white, but the ceramic material will turn light yellow when exposed to sunlight. There are two reasons for the discoloration of white alumina ceramics. One may be that the alumina ceramics deliquescence, resulting in the formation of hydrated alumina. Another possibility is that some components in the alumina pottery have changed in a high temperature environment. For example, titanium oxide is an oxide that will change color after high temperature, and this change process is irreversible.

In summary, the discoloration of alumina ceramics is the result of the oxidation of the material. In addition to ceramics, other materials will also have this characteristic. This phenomenon is generally difficult to avoid.