Chemical states of fluorine in CaF2 –CaO–SiO2 and NaF–Na2 O–SiO2 glassy slags from the perspective of electronic polarisability

Abstract Measurements of densities and refractive indices at 632·8 nm were carried out for glassy slags from the systems CaF2–CaO–SiO2 and NaF–Na2O–SiO2 at room temperature to derive the electronic polarisability of F (αF). First, αF was derived assuming that the fluorides did not depolymerise the silicate network. Values of αF for xCaF2–(100–x)(CaO.SiO2) and x(2NaF)–(100–x)(3Na2O.7SiO2) increased with increasing concentrations of CaF2 and NaF and approached those of αF for single crystal CaF2 and NaF, respectively. Values of αF for 5CaF2 – xCaO–ySiO2 also increased with increasing basicity of (mol-%CaO)/(mol-%SiO2). Smaller values of αF suggest that F ions are in more covalent bonding than CaF2 and NaF, leading to the possibility of forming Si–F bonds in the slags. Second, the number ratio of F forming Si–F bonds (NF(in Si–F)) to the total F(NTotal F) was calculated assuming that part of the fluoride depolymerised the silicate network. The NF(in Si–F)/NTotal F ratios decreased with decreasing number of b...