STARTING MATERIAL ALUMINA FOR PRODUCTION OF SAPPHIRE SINGLE CRYSTAL AND METHOD FOR PRODUCING SAPPHIRE SINGLE CRYSTAL

摘要

Disclosed is an alumina raw material for the production of a sapphire single crystal, which contains at least one element X selected from the group consisting of elements (1) to (3) shown below, wherein the concentration of the element X is 10 ppm or more and 1,000 ppm or less expressed in terms of atoms, and each concentration of silicon (Si), gallium (Ga), germanium (Ge) and tin (Sn) is 10 ppm or less expressed in terms of atoms.Element X:(1) Element having an ionic radius of 0.3 Å or less, and a valence of 3(2) Element having an ionic radius of 0.4 Å or more and 0.5 Å or less, and a valence of 4(3) Element having an ionic radius of 0.6 Å or more and 0.7 Å or less, and a valence of 4 or 5.