Composition dependence of the structure and optical properties of CuCrO2 powders

CuCrO2 powders have been prepared by solid state reaction method followed by thermal treatments at 850 °C for 4 h in air. Effects of mole ratio variation (Cr/Cu=1.03, 1, 0.95) on the morphological, structural and optical properties of CuCrO2 powders have been investigated. Both X-ray diffraction and Raman measurements indicate that the CuCrO2 powders belong to the delafossite structure. The Cr/Cu ratio drives the structural phase transition from multiphase coexistence to single CuCrO2 phase. Morphological images reveal that the CuCrO2 powder (Cr/Cu=1) exhibits a clear lamellae hexagonal structure whereas the Cr-rich sample (Cr/Cu=1.03) shows a distinct blocky structure, which possibly attributed to the Cr2O3 grains coating on those of CuCrO2. The optical absorption spectra of the as-prepared powders show that CuCrO2 has an indirect band gap of 1.64 eV.