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The intermediates obtained from thermal decomposition of Zn/Cr-layered double hydroxide carbonates (Zr/Cr-LDH; Zn0.66Cr0.34(OH)2(CO3)0.170.57H2O) were studied by XRD, TPD, FT-IR, ESCA and chemical analyses. It was found that Cr(III) ions embedded originally in the hydroxide layers were oxidized to Cr(VI) species in the temperature range between 473 and 773 K where the layer structure was lost, and reduced again to Cr(III) in the spinel phase over 773 K.

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A Zn/Ga-layered double hydroxide (LDH) with CO32− ions was prepared by coprecipitation method. The well crystallized powder was obtained and analyzed by XRD and FT-IR. Its thermal decomposition behavior studied by TG-GC system indicated that almost half of CO32− ions remained in the poorly crystallized oxide matrix even at 773 K.