N. L. Peterson

Tracer diffusion and electrical conductivity in sodium-cesium silicate glasses☆

Abstract The tracer diffusion coefficients of 22Na and 137Cs, and the electrical conductivity have been measured in the (Na, Cs)2O:3SiO2 glasses as a function of temperature and Cs/Na ratio. Complex impedance analysis was used for the conductivity measurements. The Haven ratio at 396.5°C increases from 0.3–0.4 in single-alkali glasses to 0.8 for the mixed-alkali compositions. The results are explained in terms of a single-jump mechanism; interactions between alkali ions and non-bridging oxygen ions, and between different alkali ions, produce the observed correlation effects.

The mixed alkali effect in lithium-sodium borate glasses☆

Abstract The electrical conductivity of a series of 0.35 (Li, Na)2O·B2O3 glasses shows a minimum at the composition Na/(Na+Li)∼0.6, which becomes stronger as the temperature is decreased; the activation enthalpy for electrical conductivity shows a maximum at this composition. In general, replacing 1% of the total oxygen concentration by chlorine or bromine (keeping the total alkali content fixed) in these glasses increases the conductivity; fluorine doping has an opposite effect. The mixed alkali effect, expressed in terms of the compositional dependence of the activation enthalpy for conductivity, is enhanced when borate glass is doped with fluorine, but is slightly diminished when doped with chlorine or bromine. The results are explained in terms of the structure of halogenated alkali-borate glasses, and discussed in relation to the origin of the mixed alkali effect.

Mixed isotope electrical conductivity in lithium borate glasses

Abstract Electrical conductivity of (Li 6 /Li 7 ) 2 O·3B 2 O 3 glasses with varying Li 6 /Li 7 ratios has been measured as a function of temperature. The conductivity obtained after complex impedance analysis decreases continously and the activation enthalpy increases slightly as Li 7 is substituted for Li 6 . This suggest that the difference in mass of the alkali ions is not the cause of the mixed alkali effect.

Non-classical diffusion of lithium in lithium borate glasses

Abstract The electrical conductivity, σ as a function of the 6Li/7Li ratio in a series of (6Li/7Li)2O : 2·88 B2O3 glasses does not follow classical diffusion theory, in that the σ6/σ7 ratio is a function of temperature. The data are interpreted in terms of an absolute-reaction-rate theory incorporating quantum partition functions.

Ionic transport in sodium germanate glasses

Measurements of the electrical conductivity and tracer diffusion coefficient have been made for a series of XNa/sub 2/0:(1-X)GeO/sub 2/ glasses, where X = 0.01, 0.05, 0.10, 0.15, 0.19, and 0.29. The Haven ratios determined from these measurements show the same trends as earlier work. The dc conductivities of the present study also show the same minimum in sodium ion mobility (at X approx.0.09) as found in the earlier studies. The minimum is shown to be an interplay between the pre-exponential and exponential terms. The activation enthalpy remains almost constant for X less than or equal to 0.09 and then decreases rapidly with increasing X. These changes can be related to the average Ge-Ge separation which varies little below X approx.0.08 but rapidly increases for larger X.