What are ceramics?
Ceramics are hard, brittle materials made by shaping and then firing (baking) inorganic raw materials at a very high temperature. Traditional ceramics are made mainly from clay, whose main component is kaolin (aluminosilicate) containing aluminium, silicon and oxygen (for example Al2O3·2SiO2·2H2O).
How ceramics are made
Clay is mixed with water, moulded into shape, dried, and then fired in a kiln at temperatures often above 1000 °C. Firing drives off water and causes the particles to bond strongly, giving a rigid, permanent structure.
Key idea
The strong ionic and covalent bonds in ceramics make them hard, chemically inert, heat-resistant and electrical insulators with very high melting points — but the same rigid bonding makes them brittle (they crack rather than bend).
Properties and uses
| Property | Use |
| Very high melting point, heat resistant | Furnace linings, spark plugs |
| Hard and strong under compression | Tiles, bricks, pottery |
| Chemically inert | Laboratory crucibles, tableware |
| Electrical insulator | Insulators on power lines |
Worked example
Why is a ceramic used to line the inside of a furnace? A ceramic has a very high melting point and is heat-resistant and chemically inert, so it stays solid and unreactive at the extreme temperatures inside the furnace, protecting the outer metal shell.
Remember
- Ceramics are made from clay (aluminosilicate/kaolin) by firing at high temperature.
- They are hard, heat-resistant, chemically inert and electrical insulators.
- Their main weakness is that they are brittle.