Investigations of structure and protonic conductivity in composites of hydrous antimony(V) oxide and mordenite

Abstract

Composites prepared by hydrolysis of antimony pentachloride in the presence of the zeolite mordenite have been characterised by X-ray powder diffractometry (XRD), ²⁹Si and ²⁷AL MAS NMR, ¹²¹Sb Mössbauer spectroscopy and investigations of ac conductivity as a function of relative humidity (RH). Both XRD and MAS NMR studies show degradation of the zeolite framework, the extent of the damage depending upon the amount of antimony pentachloride used in the preparation. Mössbauer spectra are consistent with the antimony-containing component being amorphous antimonic acid, as anticipated from the preparative conditions. The composites are protonic (H ⁺) conductors, but do not show the enhanced conductivities characteristic of ‘tin mordenites’, which show the same disruption of the zeolite framework.