ADDITION EFFECT OF ALKALI-EARTH METAL-OXIDES ON MOTHER GLASS OF ALKALI DURABLE POROUS-GLASS

The addition effect of alkali-earth metal oxides to the mother glass of alkali durable porous glass has been experimentally examined, and following results were obtained. The composition of the mother glass employed in this report was 57.2SiO2.22.8B2O3.5.7Na2O.9.2RO (R = Mg, Ca, Sr, Ba).3.2ZrO2.1.9Al2O3 (mol%). (1) The addition effect of alkali-earth metal oxides on the phase separation rate of mother glass was largest for MgO, followed by, in the decreasing order, CaO, SrO and BaO. (2) The addition effect of alkali-earth metal oxides on ZrO2 content in the skeleton of porous glass is not obvious now, but it may be closely associated with the phase separation rate of mother glass. (3) The addition of alkali-earth metal oxide was effective for retaining ZrO2 in the skeleton of porous glass.