Abstract: A method for manufacturing a boride single crystal is provided, wherein an initial melt region formed from an ingredient powder including an excessive content of boron than a stoichiometric composition of a boride is provided at one end in the longitudinal direction of a feed rod formed from a ingredient powder containing boron and a metallic element that constitute the boride, the initial melt region is heated to melt so as to form a molten zone, and the molten zone is moved toward the other end of the feed rod along the longitudinal direction, so as to grow the boride single crystal in a portion of the feed rod that the molten zone has passed. A substrate formed by the manufacturing method and particularly suitable for epitaxial growing a semiconductor layer such as a GaN-based semiconductor layer thereon is also provided.

Abstract: Disclosed is a chrysoberyl cat's-eye synthetic single crystal, which comprises aluminum oxide and beryllium oxide as main component, and 0.005 to 1.050% by weight, based on the total crystal, of at least one member selected from oxides of iron, cerium, vanadium, cobalt, tungsten, chromium, nickel and manganese and 0.005 to 2.0% by weight, based on the total crystal, of at least one member selected from oxides of titanium, tin, zirconium and germanium.This synthetic single crystal is comparable to natural cat's-eye in the physical properties, color tone and chatoyancy effect.