Soret coefficients of alkali oxides in alkali borate glass melts

We measured the Soret coefficients of alkali oxides in binary alkali borate glass melts. The alkali borate glasses, 15(mol %)Li2O–85B2O3, 15Na2O–85B2O3, and 15K2O–85B2O3, were encapsulated in platinum capsules and heat-treated at 1000°C with a temperature gradient in a tube furnace. After the heat treatment, the compositional distribution of the glass sample was measured by Raman spectroscopy. The Soret coefficients of the alkali oxides Li2O, Na2O, and K2O increased with the atomic numbers of the alkali metal ions. This indicates that alkali oxides more easily have high concentration in cold regions as the atomic numbers of the alkali metal ions in the alkali oxides increase. This result provides new information about the diffusion properties in glass melts.