High purity alumina (Al₂O₃ content > 99%) ceramics are ideal for high temperature applications. Re-crystallised alumina is used in crucibles as it offers the best thermal shock resistance due to the larger grain size (up to 200m m is advantageous).

Such high purity alumina shows considerable resistance to chemical attack due to the lack of glassy phases that tend to determine corrosion resistance.

The electrical and dielectrical properties generally improve with increasing purity. Electrical resistance is greatest and dielectrical loss factor is lowest in materials of highest alumina content.

High purity alumina produces a dense and essentially single-phase ceramic on sintering. Grain growth during sintering can be controlled by small additions of MgO up to 0.05%. The product usually contains a small amount of closed porosity but this can be kept below 0.5% using modern firing techniques.

Typical microstructure observed in high purity recrystallised alumina

• High purity alumina (99.8%)

• Ultra high purity alumina (99.99%)

• Ideal for high temperature applications

• Recrystallised alumina for thermal shock protection

• Highly resistant to chemical attack