Crystal structure, classification and properties of alumina ceramic substrate

Alumina has many homogenous crystals, such as α-Al2o3, β-Al2o3, γ-Al2o3, etc. Among them, α-Al2o3 has higher stability, its crystal structure is compact, physical and chemical properties are stable, and it has density and mechanical properties. The advantage of higher strength has more applications in industry.

Alumina ceramics are classified by alumina purity. Alumina purity >99% is called corundum porcelain, and alumina purity of 99%, 95% and 90% is called 99 porcelain, 95 porcelain and 90 porcelain. The content is> 85% of alumina ceramics are generally called high alumina ceramics. The bulk density of 99.5% alumina ceramics is 3.95g/cm3, the bending strength is 395MPa, the linear expansion coefficient is 8.1×10-6, the thermal conductivity is 32W/(m·K), and the insulation strength is 18KV/mm.