Ionic conductvity and NMR investigation of quaternary glasses in the ZrF 4BaF 2ThF 4LiF system

Abstract

The existence of glasses involving large amounts of LiF (up to 60%) within the ZrF 4BaF 2ThF 4LiF quaternary systems has allowed the authors to study the evolution of transport properties with varying LiF content. A minimum of ionic conductivity bound to a maximum of activation energy has been detected when the atomic Li/F ratio is equal to ≅ 0.07. In the Li-low concentration domain, σ increases regularly and ΔE decreases simultaneously when the BaF 2 concentration increases; on the contrary in the Li-high concentration region log σ and ΔE are quasi-linear functions, increasing and decreasing respectively, of the LiF rate. A 7Li and 19F NMR investigation has shown that Li + and F − ions are simultaneously mobile and the temperature dependence of the number of mobile F − ions has been determined. In the Li-low concentration domain transport properties result from mixed contributions of mobile Li + and F − ions, for high Li concentrations they depends only on the Li + rate. Glasses with high Li-content have good electrical performnces (e.g. σ 175°C ≅ 2.10 −4 ω −1 cm −1 for Zr 0.20 Ba 0.10 Li 0.60 Th 0.10 F 2).