Josef C. Lapp

The mixed alkali effect in lithium-sodium aluminosilicate glasses

The electrical conductivity of several series of lithium-sodium aluminosilicate glasses has been measured. The results indicate that the mixed alkali effect increases in magnitude with increasing alumina concentration, even though the total alkali oxide content of all glasses considered is identical. These results further indicate that the non-bridging oxygen content of the glass has no significant role in the mechanism responsible for the mixed alkali effect. Results of this study are discussed in terms of current theories proposed to explain this anomalous behavior.

The mixed alkali effect in sodium and potassium galliosilicate glasses II. DC electrical conductivity

Abstract The DC electrical conductivities of several series of mixed alkali galliosilicate glasses have been measured. The appearance of a minimum in the electrical conductivity of these glasses, independent of the gallium content, suggests that the mixed alkali effect is independent of the non-bridging oxygen content. These results are discussed in terms of current theories proposed to explain this anomalous behaviour.

The mixed alkali effect in sodium and potassium galliosilicate glasses: I. Glass transformation temperatures☆

Abstract The glass transformation temperatures of several series of mixed alkali galliosilicate glasses have been measured. The non-bridging oxygen content of these glasses is proposed to depend on the gallium to alkali ion ratio, Ga/R. The appearance of minima in the glass transformation temperatures as a function of the soda to total alkali oxide ratio, but independent of Ga/R, indicates that a mixed alkali effect occurs in these glasses even in the absence of alkali ions associated with non-bridging oxygen ions.

Physical and optical properties of R‐Zn‐Ba‐Yb‐Th fluoride glasses

The effect of glass composition on the density, refractive index, thermal expansion coefficient, glass transformation temperature, viscosity, and crystallization temperatures of R‐Zn‐Ba‐Yb‐Th fluoride glasses (R=Li or Na) was measured as BaF2 was replaced by RF. The optical spectra of these glasses were also measured. Values of each of the physical properties decreased with increasing alkali fluoride concentration. In every case, lithium had a larger effect than did sodium on the value measured for a given property. These results indicate that the substitution of an alkali fluoride for barium fluoride results in a decrease in the degree of linkage of the vitreous network.

Crystallization of lithium alumino / galliosilicate glasses

Abstract The effect of glass composition on the crystallization temperature, activation energy for crystallization, and identity of the crystalline phases formed was determined for a large number of lithium gallio and alumino/galliosilicate glasses using differential thermal analysis and X-ray diffraction. A large region exists in the ternary system lithia-gallia-silica in which LiGaSi2O6 is the only crystalline phase formed. The devitrification of glasses containing both gallia and alumina resulted in the formation of solid solutions between the lithium galliosilicate and lithium aluminosilicate phases. These data suggest that gallium and aluminum ions occupy identical sites in the glass structure.