Fluoride solid electrolytes: From microcrystalline to nanostructured tysonite-type La0.95Ba0.05F2.95

Abstract Pure tysonite La 0.95 Ba 0.05 F 2.95 is nanostructured by using the ball-milling technique. Size and pollution rate are minimized using the statistical method of Design of Experiment. The nanocrystalline powders are studied by X-ray and TEM analyses and by 19 F solid state NMR and impedance spectroscopies. Specific surface area and F/OH substitution rate are estimated by BET measurements and thermal analysis (TGA-MS), respectively. Fluorine environments and mobilities are discussed on the basis of 19 F solid state NMR data, both prior and after thermal treatment. The ionic conductivity, evaluated from sintered pellets, is compared at different thermal treatment temperatures. Thermal treatment tends to reduce microstrains up to 500 °C and to increase the grain size above this temperature. Optimal conductivity is obtained for a thermal treatment from 700 °C and no significant improvement of the conductivity by nanostructuration is observed.