Zirconias partially stabilised with either Magnesia or Yttria have excellent mechanical properties at high temperatures and are relatively inert to hostile environments. They have good impact and thermal shock resistance and are used in refractory applications. Their resistance to attack by most molten metals means they are often used as crucible materials. Their high hardness and wear resistance lead to uses such as extrusion dies and high temperature nozzles. At higher temperatures they become conducting and are used as heating elements. They have also been used as thermal barrier coatings for gas turbine blades.