| 摘要 |
<p>Glas composition having the properties which are characteristic of the crystal, that is to say a density of at least 2.90, a refraction index of at least 1.545 as well as a characteristic sonority and a high limpidity, but free of any toxic element and particularly free of lead and baryum, the composition being characterized in that it contains in weight percent: 53.0 to 58.0 of silica SiO2; 6.0 to 10.0 of potassium oxide K2O; 4.5 to 7.5 of sodium oxide Na2O; 0.0 to 9.0 of calcium oxide CaO; 0.0 to 12.0 of strontium oxide SrO; 16.0 to 21.0 of zinc oxide ZnO; 0.5 to 1.5 of antimony oxide Sb2O3; 0.0 to 1.5 of aluminium oxide Al2O3; 0.0 to 2.5 of tin oxide SnO2; 0.0 to 1.2 of boron oxide B2O3; 0.0 to 3.0 of lanthanum oxyde La2O3; 0.0 to 2.0 of titanium oxide TiO2; 0.0 to 0.3 of lithium oxide Li2O. The sum of calcium, strontium and zinc oxides being comprised between 26.5 and 31 %, with the additional conditions that, when SrO = 0, CaO may reach 9; and when SrO ¸ 0, CaO is comprised between 0 and the complement to 31, less the sum SrO + ZnO.</p> |
