A mixed isotope effect in lithium borate glasses

The effect on electrical properties of the mass difference between the two isotopes of a single alkali was investigated and compared with the effect of mixing two different alkalis. Mixed alkali borate glasses containing 0.2 total mole fraction of 6Li2O + 7Li2O were studied. DC and ac resistivities were measured at different temperatures and activation energies were computed. A maximum in activation energy at about equal mole ratios of 6Li2O and 7Li2O were observed with a minimum in the temperature independent resistivity term. Minima were also observed in both dielectric constant and dielectric loss at the same mass ratio. It is concluded that the mass difference between the two alkali ions contributes to the mixed alkali effect. (author)