Fourier Transform Infrared and Raman Spectroscopic Study of the Local Structure of Mg-, Ni-, and CoHydrotalcites

Synthetic Mg-, Ni- (takovite), and Co-hydrotalcite are characterized by FT-IR and FT-Raman spectroscopy. Changes in the composition brought about by changing the divalent metal result in small but significant changes in band positions of the modes related to the hydroxyl groups, as each hydroxyl group in the hydrotalcite structure is coordinated to three metal cations. It has also a similar effect on the interlayer water and carbonate band positions as evidenced by small shifts in band positions and the occurrence of doublets, especially for the interlayer carbonate ions. The carbonate doublets are due to site symmetry lowering.