Thermal conductivities of alkali–silicate and calcium–alkali–silicate melts

Abstract Thermal conductivities of alkali–silicate (R2O–SiO2 (R = Li, Na, K)) and calcium–alkali–silicate (CaO–R2O–SiO2 (R = Li, Na, K)) melts were evaluated by combining their thermal effusivities measured using the front-heating front-detection laser flash method with their density and specific heat capacity. Results of the evaluation revealed that the temperature-dependences of the thermal conductivities of the R2O–SiO2 and CaO–R2O–SiO2 (R = Li, Na, K) melts are small over the temperature range investigated. Moreover, the thermal conductivities of the CaO–R2O–SiO2 melts are almost equal to those of the R2O–SiO2 melts. Therefore, the network frame of the CaO–R2O–SiO2 melts can presumably become dense owing to the ion bonding between Ca2+ and the non-bridging oxygen.