Polycrystalline samples were prepared by the electrochemical reduction of pressed and sintered powder. The H content of the bronze was determined by redox titration. The electrode potential showed that the bronze was thermodynamically unstable with respect to decomposition into Nb2O5 and gaseous H. The H loss obeyed a second-order rate law. The electrode potential obeyed Nernst’s law, with a second-power dependence upon the H content. The specific resistance of H0.18Nb2O5 at 30C, as determined by 4-point direct-current measurements, was of the order of 0.011cm. The protonic conductivity of the bronze was confirmed by polarization experiments, and the diffusion coefficient of H• was estimated to be equal to 5 x 10-9cm2/s, on the basis of the rate law of the depolarization voltage.

G.Schwitzgebel, T.Unruh: Journal of Solid State Chemistry, 1995, 115[1], 260-4