Structure induced modification on thermoelectric and optical properties by Mg doping in CuCrO2 nanocrystals

Abstract

P-type semiconductors draw special attention because of its application in high-temperature thermoelectric devices and sensors. Oxide materials showing a negative temperature coefficient of resistance at high-temperatures make them good substitutes as one leg of the devices. Proper doping makes CuCrO2 a potential P-type semiconductor for TE application. The study incorporate Mg2+ for Cr3+ site in delafossite CuCrO2 crystal lattice. High-temperature solid-state reaction route has been chosen for the synthesis CuCrMgO2, by taking appropriate proportion of Cu2O, Cr2O3, and MgO. The structural studies were done by XRD, Raman analysis, FTIR, and SEM. CuCrMgO2 pellets with a thickness of 2 mm and a diameter of 13 mm were prepared for thermoelectric studies. By varying doping percentages, considerable changes in conductivity were observed. The highest conductivity of 1149.42 S/m was obtained for 1.5 wt% sample at 600 °C. It was observed that the electrical conductivity increased with the increase of doping percentages while the Seebeck coefficient decreased, which led to a maximum increase of 1.95 times in the power factor of CuCrO2. The maximum power factor of 1.2153 × 10−4 W/mK2 was calculated for 0.5 wt% doped sample at 600 °C. The electronic spectroscopic studies at ambient conditions reveal weak absorbance in the wavelength range of 300–400 nm for all samples. It is also found that increased absorbance, and direct optical band gap variation between 3.35 and 3.44 eV with doping.