SOLID STATE THERMAL CONVERSION OF POLYCRYSTALLINE ALUMINA TOSAPPHIRE

• Main Authors: KALISZEWSKI, MARY S, SCOTT, CURTIS E, LEVINSON, LIONEL M, MAXWELL, RANDOLPH E
• Format: Patent
• Language: English; French
• Published: 25.03.1995
• Edition: 7
• Subjects: AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUSPOLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR; ARTIFICIAL STONE; CEMENTS; CERAMICS; CHEMISTRY; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDINGMATERIALS; CONCRETE; CRYSTAL GROWTH; LIME, MAGNESIA; METALLURGY; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITHDEFINED STRUCTURE; REFINING BY ZONE-MELTING OF MATERIAL; REFRACTORIES; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITHDEFINED STRUCTURE; SINGLE-CRYSTAL-GROWTH; SLAG; TREATMENT OF NATURAL STONE; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL ORUNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL

SOLID STATE THERMAL CONVERSION OF POLYCRYSTALLINE ALUMINA TO SAPPHIRE A solid state process for the bulk conversion of a dense polycrystalline ceramic body to a single crystal body has been accomplished by heating the polycrystalline material to a temperature above onehalf of the melting temperature of the material but below the melting point of the material. As the process is a solid state process, no melting of the ceramic body is necessary to convert it to a single crystal. The process has been used to convert a dense polycrystalline alumina body (PCA) containing less than 100 wppm of magnesia to sapphire (single crystal alumina) by heating the PCA to temperatures above 1100.degree.C but below 2050.degree.C, the melting point of alumina.