Refractory

A refractory material is a material that retains its strength at high temperatures. "...non-metallic materials having those chemical and physical properties that make them applicable for structures, or as components of systems, that are exposed to environments above 1,000 °F (811 K; 538 °C)."
Refractory materials are used in furnaces, kilns, incinerators, and reactors. They are also used to make crucibles and molds for casting glass and metals.