Influences of Na2O, K2O and Li2O Additions on Electrical Conductivity of CaO-SiO2-(Al2O3) Melts

The influences of Na2O, K2O and Li2O additions on the electrical conductivity of CaO-SiO2-(Al2O3) melts are investigated by the four-electrode method. It is concluded that the electrical conductivity monotonously increases as increasing R2O (R=Li, Na, K) content at a fixed CaO/SiO2 ratio of 1.1. As gradually substituting Na2O or K2O for Li2O, respectively, the mixed alkali effect occurs, and there is a minimum value of electrical conductivity. Furthermore, the presence of Al2O3 promotes the mixed alkali effect. Raman spectroscopy is used to illustrate the relationship between electrical conductivity and melt structure. The electrical conductivity decreased with the increase of the degree of polymerization of melt.