Effect of alkaline and alkaline-earth cations on the compressibility of aluminosilicate glasses

Abstract

Effect of alkaline and alkaline-earth cations on the compressibility of aluminosilicate glassesR. G. Kuryaeva V. S. Sobolev Institute of Geology and Mineralogy of the Siberian Branch of the RAS, Novosibirsk rufina@igm.msc.ru, tel.: 8 (383) 333 0899 Key words: aluminosilicate glasses, high pressures, compressibility of glasses and melts, structure of glasses and melts. Citation: Kuryaeva R.G. (2011), Effect of alkaline and alkaline-earth cations on the compressibility of aluminosilicate glasses, Vestn. Otd. nauk Zemle, 3, NZ6061, doi:10.2205/2011NZ000191. Introduction.Glasses are models of deep-seated melts. Of special interest are glasses that along with other oxides contain Al 2 O 3 .The traditional model for the structure of alkali (alkaline-earth) aluminosilicate glasses holds that aluminum goes into tetrahedral coordination as a network former when the molar ratio Al 2 O 3 /M(M 2 )O=1. The cations of alkaline and alkali-earth elements in such glass compensate charge in the alumo-oxygen tetrahedrons AlO 4 -1 , and is not formed connection with the non-bridge atoms of oxygen. In other words, the structure of such glass must be completely polymerized. However, there is a number of the experimental works, which testify about the presence in such glass of the non-bridge atoms of oxygen [Riebling, 1966; Stebbins, Xu, 1997].In a number of works it was also shown that the properties of aluminosilicate glasses and melts depend on what cations, one-or double-charged, enter into their structure. Works [Webb, Courtial, 1996;Kress, et al., 1988] show that the bulk moduli of melts in the CaO-Al 2 O 3 -SiO 2 system are, in general, higher than those in the Na 2 O-Al 2 O 3 -SiO 2 system. Kuryaeva 5 Kuryaeva, 2004 reported that the compressibility of tholeiite basalt glass is lower than that of the glass with alkaline basalt composition. The former, in addition to net formers, contains mainly cations of alkaline-earth elements. The composition of the latter is similar to that of tholeiite basalt glass but contains mainly cations of alkaline metals. However, natural glass of alkaline and tholeiitic basalt, besides the oxides of silicon, aluminum and alkaline (alkaline-earth) cations, contain other components, which also could influence the compressibility of glasses.In this work, for the purpose of the confirmation of the assumption about different compressibility of aluminosilicate glass and melts, which contain the cations of alkaline or alkali-earth elements expressed previously, the compressibilities of two identical aluminosilicate glasses Na 2 O•Al 2 O 3 •6SiO 2 and CaO•Al 2 O 3 •6SiO 2 are compared. The obtained results are discussed from the point of view of the different degree of polymerization of their structural network.Experimental technique and results. Glasses of Na 2 O•Al 2 O 3 •6SiO 2 and CaO•Al 2 O 3 •6SiO 2 compositions were synthesized and studied in the works [Kuryaeva, 2009;Kuryaeva, Surkov, 2010].The refractive index at high hydrostatic pressures was measured by the technique described in detail in our...