Synthesis and characterization of the semiconductor CuBi2O4 for optical and dielectric studies. Application to methyl violet degradation under visible light

This work is devoted to the synthesis, optical and dielectric properties of CuBi2O4 prepared by sol–gel route. The X-ray diffraction analysis shows that CuBi2O4 crystallizes in a tetragonal symmetry (SG: P4/cnn) with lattice parameters: a = 8.5023 A and c = 5.8250 A; the Rietveld refinement reveals a high purity of the spinel. The crystallite size (D = 47.84 nm) was calculated from the Williamson Hall-plot. The presence of Cu–O and Bi-O bonds with Cu2+ tetrahedrally coordinated is confirmed by the Raman spectroscopy. We also report the optical and dielectric properties of CuBi2O4, including the refractive index (nλ), optical (σopt) and electrical (σele) conductivities, extinction coefficient (kλ), dissipation factor (tan δ) and relaxation time (τ). The forbidden band (Eg), measured from the UV–Visible diffuse reflectance spectroscopy, is found in the range (1.50–1.55 eV) and confirmed by these approaches. Furthermore, the as-prepared compound has been successfully tested for the first time for the methyl violet degradation under visible light. The results show a conversion rate of 75% under illumination of 4 h 30 min and that the kinetics follows a first order model.