22Na diffusion and electrical conductivity of alkali-free silicate glasses

The diffusion of sodium ions in silica glasses produced by different methods and glasses in the Al2O3-R2O3-SiO2 (R = La, Pr, Nd, Sm, Tb) systems has been investigated by the radioactive tracer method. The diffusion mobility of 22Na ions in the aluminosilicate glasses containing rare-earth element oxides is close to that in the KSG silica glass prepared by high-temperature hydrolysis of silicon tetrachloride SiCl4. A comparison of the diffusion coefficients with the electrical conductivity of the glasses has demonstrated that the conduction in the KI silica glass is due to the migration of sodium ions. In the KSG glass, as well as in the aluminosilicate glasses containing rare-earth element oxides, sodium ions are not charge carriers.