| 摘要 |
PURPOSE:Boehmite which has been obtained from aluminum isopropoxide by the sol-gel method is treated with heat at high temperatures to obtain Al2O3 as a starting material for growing single crystals with no defects, especially free from bubbles, excellent clarity and good luster. CONSTITUTION:Aluminum isopropoxide is hydrolyzed, according to the sol-gel method, in an aqueous hydrochloric acid of 1-3pH at 10-20 deg. centigrade for 10-20hr to form boehmite (AlOOH). The product is heat treated at high temperature of 1,000-1,200 deg.C in air to give alpha-Al2O3. The alpha-Al2O3 is thoroughly mixed with Cr2O3 or the like, as a colorant, then pressed and sintered into a rod. The rod is set together with a seed crystal in a FZ furnace, heated for melting to allow the single crystal to grow at a speed of less than 4.0mm./hr. |
