Configurational heat capacity and viscosity of (Mg, Ca, Sr, Ba)O-Al2O3-SiO2 melts

Abstract

The configurational heat capacity, viscosity and density of a series of Mg-, Sr- and Ba-aluminosilicate melts and glasses were determined across the metaluminous/peraluminous compositional and structural join. With increasing amounts of Al2O3 in the melts, the C-p(conf) of the metaluminous Sr-, Ca- and Mg melts increases. This indicates that the range of structures within the melt have, on average, higher energy states as the number of non-bridging oxygens decreases. The C-p(conf) of the Ba-aluminosilicate melts does not change with changing Al2O3 content. In contrast to the behaviour of the alkaline-earth aluminosilicates, the C-p(conf) of peralkaline Na2O-Al2O3-SiO2 melts decreases with increasing Al2O3 content. The C-p(conf) for Na-, Ba-, Sr-, Ca- and Mg-aluminosilicate melts was found to increase with increasing field strength of the cations in the melt - for both the peraluminous and the metaluminous(peralkaline) compositions. In contrast, the viscosity of the peraluminous alkaline earth melts decreases with increasing field strength; but viscosity increases with increasing field strength in the metaluminous field.