Surface Tension and Density of Bismuth Germanate Melts as a Function of Composition and Temperature

Abstract

The surface tension and density of xBi(2)O(3)-(1-x)GeO2 (BGO) melts have been measured systematically from their respective melting points up to around 1480 K within 0.25 <= x <= 0.86. With the addition of Bi2O3, the density of this system increased smoothly with a positive curvature. Deviation of molar volume from ideality of this system melts decreased firstly, past a minimum at about x=0.4, and then increased. Partial molar volumes of Bi2O3 and GeO2 have also been calculated based on the measured density data and compared with those of a binary bismuth borate system. On increasing the content of Bi2O3, the surface tension of BGO melts increased slowly when x <similar to 0.40, past a maximum at about x=0.50, and then decreased rapidly. In addition, the temperature coefficient of surface tension remained positive within the lower content range of Bi2O3, changed sign from positive to negative at about x=0.38, and then was almost independent of the composition within the measured temperature range when the Bi2O3 content was increased further.