| 摘要 |
A glass body is formed with a crystalline surface layer by heat treatment, the glass consisting essentially of, in weight percentages, SiO2 40-57; MgO 10-22; Al2O3 30-40; As2O3 and/or Sb2O3 0.5-6 together with 0-6 of at least one supplemental oxide selected from K2O, Rb2O, Cs2O, PbO, CaO, Bi2O3 and Ta2O5. The molten glass is shaped, cooled to at least below its transformation point and heat-treated by increasing the temperature at a rate of about 5 DEG C./min. to between 860 DEG and 950 DEG C. for a sufficient time to form the surface layer and then cooled at about the same rate. A number of examples are given, some of which are transparent and the others translucent or opaque, dependent on the supplemental oxides used. |
