Infrared studies of hydrogen beta alumina

Abstract

Infrared absorption studies of hydrogen beta alumina prepared either from ammonium beta alumina or from silver beta alumina reveal an O-H stretching vibration near 3510 cm-1. This evidence, showing hydrogen to be chemically bound to the beta alumina framework, is in agreement with previous structural work on DAl11O17 and there is no evidence to support the presence of H3O+ species. No far-infrared-active mode is observed. In stoichiometric hydrogen beta alumina, HAl11O17 hydrogen is bound only to the spacer oxygen, O(5) giving rise to the 3510 cm-1 line. In non-stoichiometric hydrogen beta alumina, hydrogen is also bound to charge-compensating interstitial oxygens, with a characteristic stretching frequency of 3548 cm-1. On exposure of anhydrous HAl11O17 to the atmosphere, water is absorbed and the O(5)-H vibration is perturbed by hydrogen-bond formation with H2O. Studies of deuterated crystals and of crystals containing molecules of heavy water support the evidence obtained from work on hydrogenated material.