| 摘要 |
PROBLEM TO BE SOLVED: To provide a hard disk substrate having high shear modulus and high hardness and having fine structure which is dense and hardly generates particle fall exceeding the limit of conventional ceramics and to provide its manufacturing method. SOLUTION: The hard disk substrate characteristically comprises a mullite acicular crystal phase 1 precipitated in a glass phase 2. The overall composition of the hard disk substrate contains the main component expressed by the general formula u(CaxMgyBaz)O.vAl2O3.wSiO2 (wherein u, v and w are respectively in the range of 0.04<=u<=0.15, 0.20<=v<=0.40 and 0.50<=w<=0.70 (wherein u+v+w=1.00) and x, y and z are respectively in the range of 0.00<=x<=1.00, 0.00<=y<=1.00, 0.00<=z<=1.00 (wherein x+y+z=1.00)).
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