Raman spectra of hydrotalcites powders were obtained using a commercial spectrometer (Horiba Jobin-Yvon LabRAM HR) equipped with a CCD detector. The 532 nm line from an Argon ion laser was used to illuminate the samples at 5 mW. For in situ Raman spectroscopy, the transitions during thermal decomposition of Mg:Fe:Al HT were studied in air (50 mL(STP) min -1 ) in a high temperature cell (Linkam CCR1000). The spectra were collected in the temperature range of 25-600 °C at intervals of 20-50 °C at a heating rate 20 °C min -1 .