It was pointed out that the acidic nature of the hydration water in NbOPO4•2H2O permitted the exchange of protons for Li+ ions. The Li phase, when annealed at 773K, had a slightly distorted lattice; as compared with the Nb phosphate network. This permitted a high mobility of the Li ion. Structural modifications which were due to Li insertion were studied by means of extended X-ray absorption spectroscopy. Analysis of the spectra revealed the presence of an additional O atom, close to Nb, which was probably not bonded to the framework. The ionic conductivity of the LiNb(OH)OPO4 phase was high, and increased at temperatures of up to 880K. At higher temperatures, the Li+ ion migrated to a permanent position in the network and ionic conduction then ceased.

S.Bruque, M.M.Lara, L.Moreno, T.Ramirez-Cárdenas, J.Chaboy, M.Marziali, S.Stizza: Journal of Solid State Chemistry, 1995, 114[2], 317-25