Composition dependence of the structure and optical properties of CuCrO 2 powders

Abstract CuCrO 2 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 CuCrO 2 powders have been investigated. Both X-ray diffraction and Raman measurements indicate that the CuCrO 2 powders belong to the delafossite structure. The Cr/Cu ratio drives the structural phase transition from multiphase coexistence to single CuCrO 2 phase. Morphological images reveal that the CuCrO 2 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 Cr 2 O 3 grains coating on those of CuCrO 2 . The optical absorption spectra of the as-prepared powders show that CuCrO 2 has an indirect band gap of 1.64 eV.