The diffusion of protons in single crystals of the fast protonic conductor,

(NH4+)(H3O+)0.85Al10.15O17), was investigated at 336 to 451K using a pulsed field-gradient NMR technique. The temperature dependence of the proton diffusion coefficient was given by:

D (cm2/s) = 6.756 x 10-5exp[-0.202(eV)/kT]

Study of Proton Diffusion in NH4+-H3O+ β”-Alumina using a Pulsed Field-Gradient NMR Method. Y.T.Tsai, S.Smoot, D.H.Whitmore, J.C.Tarczon, W.P.Halperin: Solid State Ionics, 1983, 9-10[2], 1033-40