Oxide ceramics

They are characterized, compared to metals, by a very high melting temperature and great chemical stability even at high temperature.

Alumina Al₂O₃ is made from bauxite (hydrated alumina), mainly used for its properties of stability, purity, refractoriness, chemical inertia , etc.
A quarter of the alumina produced passes through the refractories.

Silica SiO₂ is a vitreous silica, due to its low coefficient of expansion and the absence of change in crystalline phases in temperature, it has an excellent resistance to thermal shock.

Zirconia ZrO₂ exists in one of the three crystalline forms (allotropic forms) monoclinic –1100 ° C - quadratic - 2300 ° C - cubic –2700 ° C (fusion). It is necessary to stabilize the zirconia in one of the high temperature structures in order to avoid fragmentation during cooling. The addition of a few percent of MgO, CaO, Y₂O₃ or CeO₂ leads to this result.

Oxide ceramics are also widely used for electronics and electrical engineering because of the great diversity of their electrical properties (ceramics for electronics represent 70% of the world market for technical ceramics):