Chemical synthesis of nanocrystalline CuAlO2 via nitrate-citrate combustion route

Abstract

The nanocrystalline delafossite CuAlO2 powder was synthesised by a sol-gel nitrate-citrate self-combustion route. Citric acid was introduced both as the chelating and reducing agent or fuel. The citric acid/metal ion ratio was adjusted to provide fuel-lean, stoichiometric or fuel-rich conditions of the redox reaction. Equimolar amounts of copper and aluminium nitrates and the citric acid were dissolved in deionized water. The sol was dried at 80 oC to obtain the gel. By increasing the temperature above 250 oC, the gel immediately ignited, forming the precursor powder. According to the X-ray diffraction analysis the phase pure delafossite was obtained only when the precursor powder was prepared from the stoichiometric redox reaction, and after the calcination for 4 h in Ar atmosphere at 920 oC. The field emission scanning electron micrographs revealed the cauliflower aspect of the calcined powder, where small primary particles formed the agglomerates. The formation of the phase pure CuAlO2 powder was also confirmed by Fourier transformed infrared spectroscopy.