Green hydrothermally synthesized ultrathin Mg-doped CuO nanoflakes: a structural, electrical and dielectric study

Abstract

In this work, pure and Mg-doped CuO (Cu_1−xMg_xO, x = 0.0, 0.02, 0.04 and 0.08) nanoflakes were synthesized by a surfactant-free hydrothermal method. X-ray diffraction patterns confirmed the formation of the single-phase monoclinic CuO crystal structure. The morphological investigations using field emission scanning electron microscopy showed that the samples possessed ultrathin nanoflake-like morphology. The internal microstructure was highlighted using high-resolution transmission electron microscopy and selected area electron diffraction investigations. Raman spectroscopy investigation confirmed the chemical bonding, structure, and phase purity of the samples. DC conductivity measurements revealed two thermally activated conduction mechanisms in low- and high-temperature ranges caused by charge carrier transitions from shallow and deep donor levels, respectively. The AC electrical conductivity and dielectric parameters were analyzed in the temperature range of 303–403 K and frequency range of 10 Hz–1 MHz. The frequency and temperature dependencies of the AC conductivity were explained in the framework of Jonscher's power law and correlated barrier hopping model. The dielectric constant and dielectric loss were analyzed as functions of frequency and temperature and the behavior coincided with Koops’ theory. Also, the study of the impedance spectra and Cole–Cole diagrams illustrated the significant role of grain boundaries in the dielectric relaxation processes.