Inorganic material composed of metallic elements and non-metallic elements, obtained by sintering, eg Zirconia.

 Zirconia (ZrO2) is a ceramic characterized by a very high refractoriness (the melting temperature of the zirconia is in the region of 2700 °C) and good chemical stability. The transformation of the tetragonal phase (stable at high temperature) to the monoclinic phase (stable at room temperature) is accompanied by a very large and destructive dimensional change (about 3%). It is for this reason that pure zirconia is stabilized tetragonal phase at room temperature by doping yttrium oxide (Y2O3), for example.

This ceramic is widely used in watchmaking and jewelry by the opportunity to give various shades as well as the fact that it is virtually scratchproof.

Below the phase diagram of zirconia based on the concentration of yttrium oxide. 


source : Haussonne, Jean-Marie; Carry, Claude; Bowsen, Paul; Barton, James, Traité des matériaux 16 : Céramiques et verres, Lausanne : les Presses polytechniques et universitaires romandes (PPUR), 2005.