Synthesis and characterization of Cu–Co–Fe hydrotalcites and their calcined products

A series of new Cu-Co-Fe compounds with the general formula Cu^sub x^Co^sub 2-x^Fe^sub 1^HT (x = 0, 0.5, 1, 1.5 and 2) has been prepared by hydrotalcite coprecipitation method. The presence of hydrotalcite phase is revealed by XRD analysis for x values of 0, 0.5 and 1. When the copper quantity is higher than 1, the malachite phase is preferentially formed. These results are confirmed by TG-DTA, FT-IR and XPS analysis. After calcination at 500 °C in air of all samples, XRD analysis reveals the presence of spinel phases such as Co^sub 3^O^sub 4^, CoFe^sub 2^O^sub 4^, CuFe^sub 2^O^sub 4^, Cu^sub x^Co^sub y^O^sub 4^ in the solids, monoclinic CuO phase when the copper content is greater or equal to 1 and haematite phase for the sample where x is equal to 2. The presence of these phases is also confirmed by XPS results. For comparison, a Co^sub 2^Fe^sub 1^OH sample has been synthesized by classical coprecipitation method and although Co^sub 2^Fe^sub 1^HT sample and Co^sub 2^Fe^sub 1^OH form a similar phase after calcination at 500 °C, Co^sub 2^Fe^sub 1^HT500 presents a higher BET value than Co^sub 2^Fe^sub 1^OH500 sample.[PUBLICATION ABSTRACT]