Improvement of the electrical properties of glass by lithia addition

The electrical properties of toughened glass insulators used in transmission lines are of great importance. The electrical properties of glass insulators can be improved, while maintaining low viscosities and other desirable forming properties, by the the depressing effect' (i.e., the effect of substituting alkaline-earth oxides for a part of the SiO[sub 2] when developing a glass composition). To satisfy some specific application needs, a combination of both the depressing effect and mixed-alkali effect should be considered. The common practice of the latter essentially relies on increasing the ratio of K[sub 2]O to Na[sub 2]O in the glass, which, from a theoretical standpoint, undoubtedly results in better electrical properties of the glass, but with some unfavorable impact on the viscosity of the glass which may preclude its regular use. However, previous studies have shown that the mixed-alkali effect varies with the types of ions present. In the present paper the authors report on an investigation of the substitution of Li[sub 2]O for K[sub 2]O, which increases the resistivity but maintains the low viscosity.