The decomposition of the layered double hydroxides of Co and Al: Phase segregation of a new single phase spinel oxide

• The Rietveld refinement of Co–Al–CO3 hydrotalcite.
• Infrared and Raman spectroscopy of Co–Al–CO3 hydrotalcite.
• The Rietveld refinement of the oxide product.
• Infrared and Raman spectroscopy of this oxide product.

Monophasic Co–Al–CO3-like layered double hydroxides has been prepared by the coprecipitation method. It has been characterised by Rietveld refinement of the X-ray powder diffraction pattern, DTA-TGA, infrared and Raman spectroscopies. Its structure is trigonal, R3¯m with cell parameters a = 0.3061(4) nm and c = 2.252 (3) nm. The decomposition of this hydrotalcite-like structure on heating up to 800 °C yields to a single phase spinel oxide. Besides, infrared and Raman spectroscopies showed the presence of spinel-like domains. The results of Rietveld refinement have revealed that this compound has the Fd3¯m space group (a = 0.8088(4) nm), with crystallographic formula [CoII0.75Al0.25]8a[CoII0.252CoIII0.77Al0.98]16dO4, which is of the general formula Co1.77Al1.23O4. This structure is also validated by the charge distribution (CD) analysis.

X-ray diffractogram and the final Rietveld refinement plot of the single phase oxide obtained from the decomposition of Co–Al–CO3 LDH at 800 °C.Figure optionsDownload as PowerPoint slide