Metal halide perovskites (MHPs) have rapidly emerged as a leading class of materials for a wide range of energy applications, including photovoltaics, light-emitting devices, and energy storage systems.

Maghemite (γ-Fe₂O₃) nanoparticles have attracted considerable interest for electronic applications due to their tunable electrical properties. Doping strategies offer an effective way to optimize their resistive behavior for use in electronic devices. In this study, cobalt (Co) was incorporated into γ-Fe₂O₃ to enhance its resistive properties. X-ray diffraction (XRD) confirmed the retention of the cubic P4₃32 phase, with Co doping inducing subtle lattice distortions due to ionic substitution. Scanning and transmission electron microscopy (SEM/TEM) revealed morphological changes, where Co incorporation influenced particle shape and size distribution. Electrical conductivity analysis demonstrated a decrease in both AC and DC conductivity with the increase in Co content, indicating enhanced resistive behavior. The increase in activation energy suggests a reduction in charge carrier mobility, leading to higher resistivity. Impedance spectroscopy further confirmed increased real and imaginary impedance values, reinforcing the role of Co in suppressing charge transport. These results position cobalt-doped maghemite as a promising material for electronic resistive devices, such as tunable resistors and negative temperature coefficient (NTC) thermistors, where controlled conductivity and stable resistive behavior are essential.

The aim of this work is to propose an electrothermal model for predicting the electron mobility, the effective thermal conductivity, and the operating temperature of AlGaN/GaN HEMT devices. The suggested model comprises an enhanced ballistic-diffusive model (BDE) coupled with a drift-diffusion model (D-D). Furthermore, the given model considers total electron mobility, which depends on mobility degradation caused by phonon interactions, surface imperfections, and carrier mobility inside the bulk GaN material. The model is validated based on available experimental and numerical results, and good concordance is observed. It is found that the degradation of the drain current is due to electron mobility and effective thermal conductivity degradation. The output characteristic’s degradation due to changing device temperature is analyzed. We demonstrate that for gate biases of −1 V, 0 V, and 1 V, operating temperatures of 390 K, 470 K, and 570 K are obtained when the drain currents are 0.1 A, 0.24 A, and 0.38 A, respectively. Furthermore, we demonstrate that the temperature is maximal in the active region. The temporal temperature evolution presents the same trends with the same amplitude compared to the experimental data, and the error does not exceed 5%.

This study explores the impact of silver substitution at the A-site on the structural, morphological, and magnetic properties of La_1−xAg_xSrMn₂O_5+δ compounds, specifically for doping levels x = 0.1 and 0.2.