Thermal decomposition of synthesised layered double hydroxides based upon Mg/(Fe,Cr) and carbonate

Thermal analysis complimented with evolved gas mass spectrometry has been applied to hydrotalcites of the pyroaurite–stitchtite series containing the carbonate anion prepared by co-precipitation and with varying Fe3+, Cr3+ trivalent cation ratio. The resulting materials were characterised by XRD, and TGA/DTG to determine the stability of the hydrotalcites synthesised. Hydrotalcites of formula Mg6(Cr0.8,Fe0.2)2(OH)16(CO3)·xH2O, Mg6(Cr0.6,Fe0.4)2(OH)16(CO3)·xH2O, Mg6(Cr0.4,Fe0.6)2(OH)16(CO3)·xH2O and Mg6(Cr0.2,Fe0.8)2(OH)16(CO3)·xH2O formed by intercalation with the carbonate anion as a function of Fe3+, Cr3+ trivalent cationic ratio show variation in the d-spacing attributed to the size of the cation.