Chiang Mai Journal of Science

     In this research work, CuB1_−xCr_xO₂ (x = 0.00, 0.01, 0.03, 0.05, and 0.07) were synthesized by using a conventional solid-state reaction method. The effects of Cr concentration on its microstructure, optical, magnetic, and dielectric properties were investigated. X-ray diffraction (XRD) results revealed the crystal structure of all samples belongs to the R-3m delafossite structure. Besides, a second phase CuCrO₂ appeared in a high Cr content sample. Scanning electron microscope (SEM) indicated that particle size of samples was about 300 nm and slightly increased with increasing the Cr content. The optical properties measured by UV-visible spectroscopy showed the absorbance peak at ~250 nm. The corresponding direct optical band gap was about 2.90 eV. The magnetic hysteresis curve measurements of all samples revealed the paramagnetic behavior at room temperature. Noticeably, the Cr-doped samples (x = 0.01−0.07) exhibited as a ferromagnetic behavior at 50 K. Furthermore, the zero-field-cooling magnetization of the Cr-doped samples shows a ferromagnetic transition temperature at ~130K. Finally, the dielectric measurement of all samples shows the colossal dielectric permittivity.