Alumina

Robert H. Doremus

The uses, processing, structure, and properties of alumina are summarized in this arti­cle. Various polymorphs of alumina and its phase relations with other oxides are described. The following properties are discussed: mechanical, thermal, thermody­namic, electrical, diffusional, chemical, and optical. Quantitative values for these properties are given in tables. The usefulness of alumina results from its high strength, melting temperature, abrasion resistance, optical transparency, and electrical resistiv­ity. Traditional uses of alumina because of these properties are furnace components, cutting tools, bearings, and gem stones; more recent applications include catalyst substrates, tubes for arc lamps, and laser hosts. Possible new uses of alumina are in electronic circuits, optical components, and biomaterials. Alumina fibers for compos­ites and optics must be pure, defect free, and cheap.