| 摘要 |
PROBLEM TO BE SOLVED: To obtain a member for rotation processing comprising a silicon nitride-based ceramics having resistance to impact resistance and suitable for formation of the surface of amirror by satisfying specific conditions in composition and crystal phase of a specific ceramic sintered compact. SOLUTION: This member for rotation processing comprises a Si3 N4 -Y2 O3 - MgO-AlN based ceramic sintered compact and the composition satisfies the following 1st to 3rd conditions. In 1st condition, when Y is A1 mol based on 1mol Si3 N4 and Mg is B1 mol and Al is C1 mol, A1 >0, B1 >0 and C1 >0 and the composition satisfies (1) -0.03<=C1 -(A1 +B1 )<=0.03(mol), (2) 0.1<=A1 +B1 + C1 <=0.4(mol) and (3) 0.2<=B1 /A1 <=1.2. In 2nd condition, Si3 N4 crystal phase comprises α-Si3 N4 phase in which a part of Si3 N4 is substituted with Y, Mg, O and Al, β-Si3 N4 phase in which a part of Si3 N4 is substituted with Al and O and glass phase in which the balance of Si3 N4 comprises either one of Al, O, N, Y and Mg. In 3rd condition, a ratio of α-Si3 N4 phase to β-Si3 N4 phase satisfies the formula 5<=[α/(α+β)]<=50(vol%). |
