materials
Materials based on Al2O3
Materials based on Al2O3 are the best known oxide ceramics, which is often used as a construction material. With reference to the existence of strong chemical bonds of the ions Al to O they have a good chemical stability, high melting point temperature (2050 °C) and the highest hardness out of all kinds of oxide ceramics. At room temperature they have a high bending strength, which decreases rapidly at the temperature above 1000 °C. Their thermal conductivity is relatively high and they have a high coefficient of thermal expansion.
Physical properties of materials based on Al2O3:
| Percentage of Al203 | % | 80 | 95 | min. 99,5 |
| Character of the material | porous | sintered | sintered | |
| Impermeability | - | perfect | perfect | |
| Weight absorbing capacity | % | 5 - 10 | 0 | 0 |
| Volume weight | g/cm3 | 2,4 | 3,75 | 3,8 |
| Bending strength | MPa | min. 30 | min. 375 | min. 300 |
| Thermal shock resistance | K | min. 250 | min. 140 | min. 150 |
| Mean coefficient of linear thermal expansion 20 – 600 °C | K-1 | 3 – 6 x 10-6 | 6 – 8 x 10-6 | 7 – 8 x 10-6 |
| Electric field intensity | kV/mm | - | Min. 25 | Min. 17 |
| Specific el. resistance at the temperature of 200 °C | Ohm.cm | Min. 5x109 | Min. 1012 | Min. 1012 |
| Specific el. resistance at the temperature of 600 °C | Ohm.cm | Min. 105 | Min. 108 | Min. 108 |