In our understanding, zirconia ceramics and alumina ceramics are both white, while silicon nitride ceramics are black. Have you seen black alumina (AL2O3) ceramics?
Black alumina ceramics is widely attention because of their unique properties, Semiconductor integrated circuit normlly need good light sensitivity, it can reduce the adverse effects of light on integrated circuits. So the black is best choose.
Aluminum(AL2O3) is usually a colorless or whitish solid, but under certain conditions it can turn black. The following is the detailed process of aluminum oxide forming black: Surface pollution: There are some pollutants on the surface of alumina, such as organic matter containing carbon, hydrogen, oxygen and other elements, or impurities containing transition metals. These impurities can act as catalysts, causing the alumina to react. Oxidation-reduction reaction: Under certain temperature and atmosphere, pollutants on the surface of alumina will undergo oxidation-reduction reaction with oxygen. These reactions can cause changes in the color of the alumina. Formation of reduction area: On the surface of alumina, due to the existence of redox reaction, a reduction area will be formed. This reduced region has different chemical properties, including changes in stoichiometry and formation of lattice defects. Formation of color centers: In the reducing region, there are some defective oxygen sites that can accommodate extra electrons. These extra electrons change the band structure of alumina, changing how it absorbs and reflects light. This causes the color of the alumina to change to black. In general, the black formation process of alumina is mainly due to the oxidation-reduction reaction initiated by the pollutants on the surface of alumina, which forms a reduced area and introduces additional electrons, which eventually causes the alumina to turn black. Black alumina can be used as a material for devices such as photodiodes, photoconductors, photodetectors, and phototransistors. Its high energy gap and good optoelectronic properties enable it to play an important role in the field of optoelectronics.
Post time: Aug-31-2023