The Rb+ - NH4+ ion-exchange kinetics of polycrystalline β"-alumina were studied. It was found that the exchange process was hindered, at 185C, by a strong association of NH4+ and O(3) spinel blocks via short N-H(1) ... O(3) H-bonds. At higher temperatures, these H bonds weakened and the NH4+ moved freely within the conduction plane. This then permitted complete NH4+ exchange. The microstructure affected Grotthus H+ motion and the NH4+ species in differing ways. The diffusion coefficients of NH4+ and H+ were deduced from the ion exchange time and the conductivity of NH4+-exchanged samples. The former ranged from 5.91 x 10-9 to 3.26 x 10-8cm2/s, and the latter ranged from 6.83 x 10-6 to 5.03 x 10-5S/cm at 80C.

A.Tan, C.K.Kuo, P.S.Nicholson: Solid State Ionics, 1992, 52[4], 357-61