Transport Mechanisms and Dielectric Features of Mg-Doped ZnO Nanocrystals for Device Applications

Abstract

Magnesium-doped zinc oxide “ZnO:Mg” nanocrystals (NCs) were fabricated using a sol gel method. The Mg concentration impact on the structural, morphological, electrical, and dielectric characteristics of ZnO:Mg NCs were inspected. X-ray diffraction (XRD) patterns display the hexagonal wurtzite structure without any additional phase. TEM images revealed the nanometric size of the particles with a spherical-like shape. The electrical conductivity of the ZnO NCs, thermally activated, was found to be dependent on the Mg content. The impedance spectra were represented via a corresponding circuit formed by a resistor and constant phase element (CPE). A non-Debye type relaxation was located through the analyses of the complex impedance. The conductivity diminished with the incorporation of the Mg element. The AC conductivity is reduced by raising the temperature. Its plot obeys the Arrhenius law demonstrating a single activation energy during the conduction process. The complex impedance highlighted the existence of a Debye-type dielectric dispersion. The various ZnO:Mg samples demonstrate high values of dielectric constant with small dielectric losses for both medium and high-frequency regions. Interestingly, the Mg doping with 3% content exhibits colossal dielectric constant (more than 2 × 104) over wide temperature and frequency ranges, with Debye-like relaxation. The study of the electrical modulus versus the frequency and at different temperatures confirms the non-Debye relaxation. The obtained results reveal the importance of the ZnO:Mg NCs for device applications. This encourages their application in energy storage.

Extremely Reduced Dielectric Constant and Band Gap Enhancement in Few-Layered Tungsten Disulfide Nanosheets

“…The decrease in the dielectric constant with the increase in the frequency is due to contribution of the dipole, electronic, ionic polarization, and charge polarization. At higher frequency, the nano dipole fails to keep up with the speedy differences of electric field, and hence, it exhibits no dispersion with the electric field, resulting in exponential decay in the dielectric constant. , Moreover, the bulk WS 2 shows a very high dielectric constant of 7482373 at 100 Hz and ∼10000 at 2 MHz (Figure c). The results show an unusual trend, and despite increasing the dielectric constant, an extreme reduction of about 1426 times in the dielectric constant was observed for the WS 2 nanosheet.…”

“…However, synthesis of the pure and crystalline WS 2 nanosheet is very crucial. Cao et al recently reported a lightweight and high-performance microwave absorber based on 2D WS 2 –RGO heterostructures synthesized via a facile one-step hydrothermal approach, which exhibited an effective absorption bandwidth due to the interfacial dielectric coupling effect. , They have also observed the synergetic dielectric loss and magnetic loss toward microwave absorption through hybridization of WS 2 nanosheets and NiO nanoparticles. , Heterostructures of Co 3 O 4 clusters–WS 2 nanosheets as efficient microwave absorption structures were also reported, and it has been shown that the dielectric property of the WS 2 played an important role in achieving the high efficiency of the devices. − Moreover, to fabricate nanoscale devices such as LEDs, optoelectronic devices, and energy storage/generation devices, the tuning of the band gap and dielectric constant is urgently needed . However, the dielectric constant of pristine WS 2 nanosheets grown by the hydrothermal route is not yet reported.…”

“…23−26 Moreover, to fabricate nanoscale devices such as LEDs, optoelectronic devices, and energy storage/generation devices, the tuning of the band gap and dielectric constant is urgently needed. 27 WS 2 nanosheets grown by the hydrothermal route is not yet reported. Various methods, such as mechanical pulverization, liquid phase sonication, ion interaction, and electrochemical exfoliation techniques, have been used to grow the WS 2 nanosheets; however, these routes involved complicated processing steps, and controlling the shape and size of the materials via these methods is more challenging.…”

Mixed Ionic and Electronic Conduction in TeO2-ZnO-V2O5 Glasses towards Good Dielectric Features

“…The result shows a non-Debye-type relaxation for all samples. The deviation to a Debye profile in the current system could be attributed to the formation of macroscopic dipole groups and/or the formation of non-polar clusters [ 17 ].…”

“…The semicircles were well-fitted based on the expressions of both and : where R b and A b designed the resistive and capacitive components of the bulk region, respectively. R int and A int are the resistive and capacitive components of the interfacial impedance that correspondingly determine the space charge polarization [ 17 ]. The parameters n 1 and n 2 are the exponential indexes relatives to the bulk region and the interface.…”