Vibrational modes in layered double hydroxides and their calcined derivatives

Vibrational modes of layered double hydroxides and their calcined derivatives in the region of 60-4000 cm(-1) have been studied using a combination of inelastic neutron scattering (INS), Fourier transform infrared (FTIR) and Raman spectroscopies. The INS spectra recorded at 30 K are dominated by the vibrational contribution of the water contained in the negatively charged layers. Using FTIR and Raman assignments of LDHs and magnesium hydroxide, the lattice modes of the moieties present in the positively charged layers have been identified and assigned. We infer from the results that the vibrational modes of the cationic layer are unaffected by change in the identity of the interlayer anions and that the hydroxyl bonds are strengthened by thermal activation. (C) 1998 Published by Elsevier Science B.V. All rights reserved.