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.