| 摘要 |
PURPOSE: To provide a polycrystalline ceramic product excellent in transparency and excellent also in strength, hardness and workability by thermally decomposing fine powder obtd. by spray-drying an aluminum salt soln., compacting and sintering the resultant aluminum oxide or a mixture of the oxide with magnesium oxide and then carrying out HIP. CONSTITUTION: Fine powder obtd. by spray-drying an aluminum salt soln. is thermally decomposed to form aluminum oxide. An org. binder is added to the aluminum oxide or a mixture of the oxide with <=0.05wt.% magnesium oxide and they are compacted in a desired shape. The resultant compact is sintered at 1,280-1,300 deg.C in the air and the sintered compact is subjected to hot isostatic pressing under the conditions of 1,300-1,310 deg.C and 1,000-2,000atm to obtain the objective polycrystalline ceramic product consisting of crystals of <=2.0μm average diameter, not contg. coarse grains of >=4μm in the interior and having <=0.1μm internal pore diameter, a Vickers hardness Hv of >=2,000, >=70kg/mm<2> bending strength, a specific gravity of 3.99 and transparency. |
