Surface tension of bismuth borosilicate melts

The surface tension of Bi2O3–B2O3–SiO2 melts was measured using the ring method over the temperature range 973–1573 K. The composition and temperature dependences of the surface tension were investigated. The surface tension of Bi2O3–B2O3–SiO2 melts showed a maximum near 60–70 mol% Bi2O3 and decreased with increasing B2O3/SiO2 ratio at 1373 K. By assuming a linear relationship between the surface tension and the Bi2O3 content of binary silicate melts, the surface tension factor of Bi2O3 was determined to be 211 mN m−1 at 1373 K. The surface tension values calculated using the surface tension factor of each single component showed the largest deviation from the measured values when the Bi2O3 content was around 50–60% and were dependent on the B2O3 content. The temperature coefficient of surface tension had positive values at low Bi2O3 contents (less than 30–40 mol%) and negative values at high Bi2O3 contents.