Preparation of CuCr2O4 nanopowders using two different chromium sources

Abstract

CuCr2O4 spinel powders were synthesized starting from different chromium sources, namely (i) chromium oxide (α-Cr2O3) and (ii) ammonium dichromate ((NH4)2Cr2O7). The copper source was a Cu(II) carboxylate-type complex. The Cu(II) carboxylate complex was obtained by the redox reaction between Cu(NO3)2·3H2O and 1,3-propanediol (1,3PG) at 130 °C. In the first case (i), we have started from a mixture of α-Cr2O3, Cu(NO3)2·3H2O and 1,3PG that upon heating formed the copper malonate complex, which decomposed around 220 °C forming an oxide mixture (CuO + α-Cr2O3). In the second case (ii), (NH4)2Cr2O7, Cu(NO3)2·3H2O and 1,3PG were homogenously mixed. Heating this mixture at 130 °C resulted, in situ, in the Cu(II) complex. On controlled temperature increase, the violent decomposition of (NH4)2Cr2O7 took place at 180 °C along with the decomposition of the Cu(II) complex, leading to an amorphous oxide mixture of Cr2O3+x and CuO. By annealing the samples in the temperature range 400–1000 °C, the spinel phase (CuCr2O4) was obtained in both cases: (i) at 800 °C and (ii) at 600 °C as a result of the interactions between the precursors used, when the oxide system was amorphous and highly reactive. The presence of CuCr2O4 was highlighted by XRD and FTIR analyses.