Structural, optical, and dielectric properties of hydrothermally synthesized SnO₂ nanoparticles, Cu/SnO₂, and Fe/SnO₂ nanocomposites

Abstract

The structural and optical properties, as well as dielectric characteristics at various frequencies (0.1 Hz—20 MHz) and temperatures, T (300–400 K), of hydrothermally synthesized SnO2 nanoparticles, Cu/SnO2, and Fe/SnO2 composites have been investigated. The crystal structure is mostly formed of a tetragonal SnO2 phase, with a second phase of monoclinic CuO or rhombohedral Fe2O3 detected in Cu/SnO2, and Fe/SnO2 composites, respectively. The direct optical band gap, residual dielectric constant, and density of charge carriers are increased, while ac conductivity (σ ac) and dielectric constant decreased in Cu/SnO2 and Fe/SnO2. The value of σ ac was decreased while the electric Q-factor was increased by increasing T. SnO2 obeyed the hole-conduction mechanism for 400 ≥ T (K) ≥ 300, while Cu/SnO2 and Fe/SnO2 obeyed the electronic-conduction mechanism for 400 ≥ T (K) > 300. The binding energy is independent of T for SnO2, whereas it increases with rising T for Cu/SnO2 and Fe/SnO2 composites. F-factor and electronic polarizability are improved by a rise of T for SnO2 and Cu/SnO2 meanwhile are decreased for Fe/SnO2. The electrical impedance of the grains and their boundaries as well as equivalent capacitance are increased by increasing T and have higher values for Fe/SnO2 at T > 300 K. The obtained results recommend the synthesized Cu/SnO2 and Fe/SnO2 composites to be used as catalysts for water purification, anodes for lithium batteries, supercapacitors, and solar cell applications amongst others.

Electrical properties of epoxy/graphite flakes microcomposite at the percolation threshold concentration

“…This change in dielectric constant is consistent with Koop's theory and Maxwell Wagner's theory [34][35][36]. According to the theory, when epoxy/GFs microcomposites are placed in an electric field, the mobile electrons drift towards the grain boundary and get accumulated in the well due to high resistance at grain boundaries consequently, this process results in interfacial polarization [8,17,18,[34][35][36].…”

“…However, at high frequencies, the larger dipolar groups become less influential on the dielectric constant because they are unable to align at the same rate as the low frequencies. Thus, at higher frequencies, the dielectric constant of the epoxy system continuously decreases [8,17,18,[31][32][33]. This change in dielectric constant is consistent with Koop's theory and Maxwell Wagner's theory [34][35][36].…”

“…The even distribution of the filler within the polymer matrix is a fundamental challenge in sample preparation. Previous literature has presented different methods for sample preparation [8,[16][17][18]. However, we have chosen the method that we believe to be the most suitable, ensuring the effective dispersion of the microfiller within the epoxy.…”

“…However, as the frequency increased beyond 10 0 Hz, tan(δ) decreased rapidly. The presence of GFs at a concentration of 0.0625 wt% results in an increased heterogeneity within the epoxy composite, leading to the generation of free charges and a subsequent rise in tan(δ) [18]. Conversely, at concentrations of 0.125 wt% and 0.25 wt% GFs, a notable decrease is observed in tan(δ).…”

“…The Q factor of a capacitor quantifies its efficiency in managing energy losses, as shown in figure 7. In the context of an AC system, the Q factor expresses the ratio of energy stored within the capacitor to the energy dissipated as thermal losses through the equivalent series resistance [18]. An ideal capacitor has an infinite Q value, indicating that no energy is lost during energy storage.…”