The influence of composition on some physical properties of glasses in the RO—AI2O3—SiO2 system

Abstract

In glasses of the system RO—AI2O3—SiO2, the influence of the partial replacement of SiO2 by RO (R = Mg, Ca, Sr, Ba) or AI2O3 on the molar volume V1, the molar refraction RM, the mean linear thermal expansion coefficient A and on the transformation temperature has been investigated. V1, RM, A and Tg change linearly with increasing RO or AI2O3 contents. The straight lines for V1 and Rm have different gradients, depending on the alkaline earth oxide present, and intersect at a point which does not correspond with an RO content of 0 % but is dependent on the AI2O3 content. When replacing SiO2 by AI2O3, remains constant, independent of the alkaline earth oxide. This leads to the conclusion that the Al3+ cation is incorporated as a network former. At the same RO contents, a linear dependency of A on the field strength f of the alkaline earth oxide has been determined; which, however, is not so well defined in the case of the V1 and RM values. As far as the Tg behaviour is concerned, no simple relationships are apparent.