The structure of pyrochlore-type antimonic acid, HSbO3•0.5H2O, was investigated by using neutron powder diffraction techniques. It was found that the structure (Fd¯3m) contained a [Sb2O62-] framework, with interstitial O atoms present as a mixture of H2O and H3O+. Three H atom sites were identified. One site was close to the [Sb2O62-] framework, in Sb-OH hydroxyl groups. Another H site was that of water molecules which were H-bonded to framework hydroxyl ions. Finally, H was present as H3O+ ions which were H-bonded to the O-atoms of inter-cavity windows. An intra-framework equilibrium of the form: Sb-OH + H2O  Sb-O- + H3O+, provided a mechanism for intra-cavity chemical exchange and proton conduction.

R.C.T.Slade, G.P.Hall, A.Ramanan, E.Prince: Solid State Ionics, 1996, 92[3-4], 171-81