Interphase-exchange processes at the interface of fluorine-conducting solid electrolyte with alkaline solutions

Abstract

Kinetics of fluorideion exchange at the interface between a LaF3:Eu2+ single crystal and solution with different pF and pH is studied by the galvanostatic and potentiometric methods and also by impedance spectroscopy. Anodic galvanostatic transients are linearized in the coordinates ln (η–ηmax) vs. t, which suggests that the exchange rate in alkaline solutions is limited by surface diffusion of fluorine adions. The surface concentration of fluorine adions с 0 and the surface diffusion flow ν 0 are assessed. Impedance spectroscopy studies of the exchange processes indicate that the charge-transfer resistance R F and the heterogeneous reaction resistance R P increase with the increase in the рН of the fluoride-containing solution and also with the increase in the time of exposure of the fluoride-selective electrode membrane in a neutral solution with pH 6.4 and the high (pF 2) content of fluorides.