Layered double hydroxides (LDHs) containing M-II, Al-III, and Cr-III in the brucite-like layers (M = Cd, Zn) with different starting Al/Cr molar ratios and nitrate/carbonate as the interlayer anion have been prepared following the coprecipitation method at a constant pH: Zn-II-Al-III-Cr-III-CO32- at pH = 10, and Cd-II-Al-III-Cr-III-NO3- at pH = 8. Two additional M-II,Al-III-LDH samples (M = Cd, Zn) with chromate ions (CrO42-) in the interlayer have been prepared by ionic exchange at pH = 9 and 8, respectively, starting from M-II-Al-III-NO3-. The samples have been characterised by absorption atomic spectrometry, powder X-ray diffraction (PXRD), Fr-IR spectroscopy and transmission electron microscopy (TEM). Their thermal stability has been assessed by DTA-TG and mass spectrometric analysis of the evolved gases. The PXRD patterns of the solids calcined at 800 C show diffraction lines corresponding to ZnO and ZnAl2-xCrxO4 for the Zn-containing samples, and diffraction lines attributed to CdO and CdCr2O4 and (AI,Cr)(2)O-3 for the Cd-containing ones. Additionally a minority oxide, Cd2CrO5, is observed to Cd-II-Al-III-LDH samples with chromate ions in the interlayer. (C) 2011 Elsevier B.V. All rights reserved.