Chemical state of fluorine in fluoroaluminosilicate slags in glassy and molten states from perspective of electronic polarisability

AbstractThe electronic polarisability of F α F has been determined for fluoroaluminosilicate slags from density and refractive index data measured to investigate the chemical state of F in the slags and the effect of CaF2 additions on depolymerisation of the aluminosilicate network. To simulate commercial mould fluxes, synthetic slags with compositions of xCaF2–5Na2O–6Al2O3–(89–x)CaO.SiO2 were prepared as samples, where x ranged between 5 and 12·5 mol.-%. Densities and refractive indices of the slags were measured in glassy and molten states; for the melts, the sessile drop method and ellipsometry were applied to density and refractive index measurements respectively. Values of α F determined for the slags are on the whole in good agreement with those for CaF2, irrespective of temperature, which suggests that F ions in the slags are in ionic bonding of Ca–F with a possibility of a Na–F bond. However, only a glassy slag with a lower concentration of CaF2 exhibits a slightly smaller α F than CaF2, which wou...