Kinetics of solid-phase H+/M+ ion exchange on hafnium hydrogen phosphate

Abstract

The kinetics of solid-phase reactions between hafnium hydrogen phosphate and alkali metal chlorides were studied by thermogravimetry with subsequent analysis of leaving gases. For sodium and potassium chlorides, the reaction occurs in two stages; the first stages produces MHHf(PO4)2, and the second yields the MHf2(PO4)3 NASICON phosphate. For rubidium chloride, the reaction is one stage and produces Rb2Hf(PO4)2. For cesium chloride, the reaction is an analogue of the reaction for rubidium chloride, but has two stages. Kinetic data were used to determine interdiffusion coefficients for hydrogen and alkali-metal ions at various temperatures and the activation energies of interdiffusion.