Search Results (723)

Flexible oxide electronics require dielectric layers that combine low-temperature processability, low leakage current, high capacitance density, and mechanical reliability. In this work, we prepared ZrAlO_x-PVP hybrid dielectric films through a low-temperature self-combustion solution process at 180 °C and systematically investigated the effect of PVP doping (0–2 wt%). The results show that PVP promotes the formation of M-O-C related bonding environments, suggesting the construction of an organic–inorganic crosslinked structure. Moderate PVP incorporation effectively suppresses leakage pathways, whereas excessive PVP induces polymer aggregation and trap-assisted conduction. Among all samples, the film on flexible PI (polyimide) with a PVP doping concentration of 0.5 wt% exhibits the best overall performance, with a leakage current as low as 1.89 × 10⁻⁸ A/cm² at 1 MV/cm, a dielectric constant of 8.88. After static bending at a radius of 20 mm, the film maintains stable dielectric behavior, indicating improved stress tolerance. Flexible IGZO TFT fabricated with the optimized dielectric shows a mobility of 11.84 cm² V⁻¹ s⁻¹, a threshold voltage of 0.48 V, and a subthreshold swing of 0.24 V dec⁻¹ before bending. This work demonstrates that moderate PVP crosslinking provides an effective balance between defect suppression and stress relaxation, offering a practical interface-engineering strategy for low-temperature flexible high-k dielectrics. Full article

Flexible capacitive pressure sensors have garnered significant attention in wearable electronics and robotic tactile sensing due to their high flexibility and simple structure. However, non-uniform distribution of conductive fillers in composite dielectric layers often compromises dielectric stability and sensing performance. In this work, a Cu/PDMS composite dielectric layer was fabricated using ultrasonic-assisted homogenization to enhance Cu particle dispersion and suppress sedimentation. A theoretical model and finite element simulations were employed to investigate the effects of particle distribution on permittivity, capacitance, electric field, and current density. The results indicate that uniform Cu dispersion improves dielectric stability and mitigates local electric-field concentration. Compared with conventionally prepared sensors, the ultrasonically treated sensor demonstrated higher sensitivity, enhanced dielectric stability, and a broader working range. Specifically, the sensor achieved a sensitivity of 0.157 kPa⁻¹ within 0–1 kPa and maintained stable performance over 1000 loading cycles. These findings confirm that ultrasonic-assisted homogenization is an effective approach for improving the dielectric and sensing performance of flexible capacitive pressure sensors. Full article

The rapid growth in the electric vehicle sector has increased demand for advanced battery thermal management systems (BTMSs) with high heat-dissipation capacity and temperature uniformity. Immersion cooling using dielectric fluids has recently been recognized as a promising alternative technology to conventional indirect liquid cooling methods. This study investigates the thermal and hydrodynamic behaviour of a sixteen-lithium-ion cell battery (LIB) module immersed in low-viscosity dielectric fluids using three-dimensional computational fluid dynamics simulations. In this context, a total of twenty dielectric fluids are evaluated using the ANSYS Fluent solver, with particular emphasis on the effects of key thermophysical properties, including viscosity, density, specific heat capacity, and thermal conductivity. The simulation findings reveal that mineral oil and PAO4 yield the lowest maximum LIB cell temperatures, with a reduction of approximately 4 K compared to the least effective dielectric fluids, such as undecane and cumene. Moreover, in terms of temperature uniformity, mineral oil, Novec 7000, and PAO4 exhibit the most homogeneous temperature distributions among the twenty dielectric fluids. In addition, they show an improvement in the temperature uniformity index of approximately 32.4% compared with the least effective dielectric fluid, cumene. On the other hand, mineral oil and PAO4 generate significantly higher pressure drops because of their relatively high viscosities, which increases hydraulic resistance and pumping power requirements. These findings demonstrate that excellent thermal performance does not necessarily correspond to optimal overall thermo-hydraulic behaviour. Overall, the results confirm that immersion-BTMS performance is governed by a complex interaction between dielectric fluid thermophysical properties and flow behaviour, highlighting the importance of coupled thermo-hydraulic optimization in the selection of dielectric fluids for next-generation immersion-cooled battery systems. Full article

This study investigates the modulation of coercivity and magnetodielectric coupling in heat-treated, nickel-substituted lanthanum ferrite. LaFe_0.7Ni_0.3O₃ samples were synthesized by high-energy ball milling and sintered at temperatures between 1073 and 1473 K. Chemical composition, crystalline structural evolution, surface morphology, magnetic, dielectric, and electrical properties, as well as magnetodielectric coupling, were analyzed. The XPS spectra revealed the presence of adsorbed oxygen, associated with the high oxygen affinity of the material. This behavior is interpreted as a charge-compensation mechanism, related both to the formation of oxygen vacancies and to the partial oxidation of Fe³⁺ to Fe⁴⁺. XRD and Rietveld refinement confirmed a single-phase orthorhombic Pnma structure, and structural simulations revealed progressive octahedral distortions with increasing temperature, affecting the octahedral tilting and electronic bandwidth. Magnetic characterization revealed that thermal processing modifies the magnetic behavior, inducing weak ferromagnetism and a significant increase in coercivity, correlating with progressive densification, greater domain stability, and reduced microstrain. Impedance measurements revealed magnetodielectric coupling, the Maxwell–Wagner interfacial polarization mechanism, and reduced dielectric losses. These findings demonstrate that the coercivity and magnetodielectric response in cationic nickel-substituted lanthanum ferrite can be tuned through thermal processing. A semi-empirical magnetocrystalline anisotropy model is proposed to explain the coercivity evolution and associated multiferroic behaviors, thus contributing to the study of functional ferrites as sustainable alternatives to rare-earth magnetic materials with potential in sensors and memory devices. Full article

To meet the growing demand for materials combing high thermal conductivity and electrical insulation, we developed epoxy (EP) composites filled with zero-dimensional (0D) silver nanoparticles (AgNPs) and two-dimensional (2D) boron nitride nanosheets (BNNSs). This hybrid filler system synergistically enhances both thermal conductivity and dielectric properties, while retaining excellent electrical insulation. With only 1 wt% AgNPs and 15 wt% BNNSs, the composite achieved a dielectric constant of 4.17 at 100 Hz, outperforming pure EP. At 30 wt% BNNSs and the same AgNP loading, the in-plane and out-of-plane thermal conductivities reached 3.02 and 0.41 W·m⁻¹·K⁻¹, respectively, along with improved thermal stability. Moreover, the composite exhibited an electrical conductivity below 10⁻⁹ S/cm at 1000 Hz, confirming that the minimal metal filler content negligibly affects insulation. Thus, this work offers a feasible strategy for designing next-generation high-performance composites using 0D/2D hybrid fillers, highlighting their promising potential for advanced electronic packaging. Full article

With the advancement of energy storage technology, there have been significantly increased demands for the storage performance and operating temperature of capacitor dielectric materials. As a high-temperature resistant polymer, polyimide (PI) shows great potential for application as a dielectric material. In this study, binary PI composite films with various contents of yttria-stabilized zirconia particles (YZPs) were prepared via in situ polymerization. The results demonstrated that the incorporation of YZPs enhanced the breakdown resistance compared to pure PI films. Specifically, at a YZP content of 8 wt%, the breakdown strength (BDS) of the composite films reached 566 kV·mm⁻¹. Although the mechanical strength exhibited a slight reduction, the dielectric properties remained stable, leading to an overall improvement in energy storage performance. Overall, 2 wt% YZPs/PI (with 5 mol% Y₂O₃, ZPb2) film is optimal in terms of its mechanical and dielectric properties. This research establishes a solid foundation for the engineering development and industrial implementation of high-performance PI-based polymer dielectric materials. Full article

This paper presents the results of the preparation and electrical characterization of Ru–Si–O thin-film nanocomposites deposited by magnetron sputtering (pDC) with varying oxygen content ranging from 0% to 50%. Measurements were conducted over a wide frequency range of 50 Hz–5 MHz and temperatures of 20–373 K. Conductivity analysis revealed that DC conduction occurs at low frequencies (≤10³ Hz), while an increase in conductivity associated with electron tunneling mechanisms is observed at higher frequencies. The determined charge transport activation energies range from 3 × 10⁻⁴ eV for the oxygen-free sample to 6 × 10⁻² eV for the high-oxygen samples, indicating a significant effect of composition on the conduction mechanisms. In samples containing 30% and 50% oxygen, two characteristic frequency ranges for the activation of transport processes were observed (e.g., ~10²–10³ Hz and 10⁴–10⁶ Hz), suggesting the coexistence of multiple tunneling mechanisms. Phase angle analysis revealed a transition from values near –90° at 151 K to values near 0° at 333 K, characteristic of parallel RC systems. The minimum dielectric loss tangent occurs in the range of 10³–10⁵ Hz, corresponding to Maxwell–Wagner relaxation. The dispersion coefficient α reaches maximums in two frequency ranges, decreasing with increasing oxygen content. EDS analysis showed a decrease in Ru content from ~24.9 at.% (0% O₂) to ~0.7 at.% (50% O₂) and an increase in oxygen content to ~78 at.% at 10% O₂. The results confirm the transition from metallic conduction to tunneling and hopping mechanisms with increasing oxidation state of the structure. Full article

Direct current (DC) surface flashover on polystyrene (PS) remains a critical bottleneck that impedes its reliable application in high-voltage insulation apparatus. To circumvent the protracted processing durations and stringent film-forming conditions inherent in conventional surface modification techniques, this study proposes a novel “liquid-film-assisted in situ rapid plasma curing” strategy. By harnessing atmospheric-pressure dielectric barrier discharge (DBD) technology within an argon ambient, the rapid (<6 min) and efficient deposition of a fluorosilane (FAS-13) functional coating onto the substrate was achieved. Microscopic characterizations coupled with isothermal surface potential decay (SPD) measurements reveal that this coating substantially mitigates the detrapping and surface migration of charge carriers. Macroscopic DC flashover testing corroborates that, under the optimal modification ratio, the surface breakdown voltage of PS is elevated to 14.04 kV, yielding an insulation gain of 26.94%. To elucidate the underlying physical mechanisms, density functional theory (DFT) calculations were conducted, revealing that the energy band misalignment between the wide-bandgap fluorinated layer and the substrate facilitates the construction of a high-density deep trap network (with a depth of ~0.8 eV) at the coating–substrate interface. By robustly anchoring primary electrons and inducing the formation of a homopolar space charge shielding layer, these deep traps physically arrest the evolution of the secondary electron emission avalanche (SEEA). Consequently, this work not only establishes a viable engineering framework for the rapid, large-scale surface reinforcement of DC insulation equipment but also provides profound quantum chemical insights into interfacial trap regulation within all-organic dielectrics. Full article

Lead-free halide double perovskites have emerged as promising candidates for sustainable optoelectronic and thermoelectric applications due to their tunable band gaps, high stability, and non-toxic nature. In this work, we systematically investigate the structural, electronic, optical, and thermoelectric properties of novel double perovskite compounds Rb₂InCuX₆ (X = F, Cl, Br) using density functional theory (DFT) combined with spin–orbit coupling (SOC). The structural stability of these materials is confirmed by evaluating the tolerance factor, octahedral factor, and negative formation energy. Accurate band structures obtained via the modified Becke–Johnson (mBJ) potential and SOC reveal direct band gaps of 1.49 eV, 0.91 eV, and 0.56 eV for Rb₂InCuX₆ (X = F, Cl, Br), indicating their suitability for solar cell applications. Optical properties, derived from the dielectric functions calculated within the Kramers–Kronig framework over a photon energy range up to 14 eV, show strong absorption peaks in the ultraviolet region, making these materials attractive for high-frequency optical conversion devices. Furthermore, thermoelectric parameters, including the Seebeck coefficient, electrical conductivity, electronic thermal conductivity, and power factor, are computed using the BoltzTraP code. Notably, the figure of merit (ZT) approaches 0.80 for Rb₂InCuF₆, close to the ideal value of unity, demonstrating excellent thermoelectric performance over a wide temperature range (200–800 K). Our findings establish Rb₂InCuX₆ (X = F, Cl, Br) as promising lead-free double perovskites for integrated optoelectronic and thermoelectric applications. Full article

This paper systematically investigates the failure characteristics and mechanisms of insulating materials in DC voltage dividers under combined high-frequency voltage and high-temperature conditions via simulations and experiments. The results showed that high-frequency harmonics severely degrade the insulation strength of polypropylene/paper/polypropylene (PPLP) at 10 kHz, in which the bulk breakdown strength of PPLP decreases by over 50%. Furthermore, the surface flashover voltage in oil is reduced by 17.7% under high-frequency voltage alone, and by as much as 51% when white flocculent substances are present in the oil. The dielectric properties of PPLP strongly depend on frequency and temperature, which aggravate the heat accumulation of the divider under high-frequency voltage. Furthermore, the multilayer structure of PPLP introduces deeper trap levels due to interfacial states, which reduce the breakdown strength and flashover voltage of PPLP. Electro-thermal coupling induces a rapid temperature rising to 98 °C at 25 kHz caused by dielectric loss, leading to oil turbidity and white precipitation, consistent with finite element simulations. Consequently, a failure mechanism is proposed as follows: prolonged electro-thermal stress causes chain scission in styrene-containing materials, releasing monomers that repolymerize into white polystyrene deposits. Their porous structure and dielectric mismatch distort the interfacial field, trigger partial discharge, and aggravate surface flashover. Full article

In this work, a Fabry–Perot (F–P) antenna based on metal integrated suspended lines (MISLs) at the K-band for microwave wireless power transmission (MWPT) is proposed. The antenna’s contribution lies in its adaptation of the MISL structure and its all-metal design, which achieves low loss, high gain, and high-power capability. The entire antenna structure is dielectric-free, further reducing apparent dielectric loss at high frequencies. Meanwhile, the radiation structure is surrounded by a metallic wall to minimize radiation loss. A metal partially reflective surface (PRS) on the top of the antenna, together with a metal ground plane, constitutes an air-filled resonant cavity. The reflection and transmission of electromagnetic waves in the PRS are effectively controlled to be in phase, thereby enhancing its gain by optimizing the PRS and resonant cavity dimensions. A simple slot antenna is employed as the primary source for the F–P resonant cavity. The antenna is processed layer by layer and then assembled to lower machining costs and complexity. Experimental results indicate that the proposed F–P antenna achieves an aperture efficiency over 60% and a measured peak gain of 18.4 dBi at 23.85 GHz with an aperture size of 2.86 λ₀ × 2.86 λ₀. Full article

Designing an ultrashort, fast-rising high-power microwave (HPM) system requires an antenna that simultaneously provides ultrawideband (UWB) operation, high gain, and megawatt-level power handling under strict size, weight, and power (SWaP) constraints. To meet these requirements, this paper proposes an improved UWB HPM antenna that integrates a graded partial dielectric transformer (PDT) with a Koshelev-type combined antenna. The graded PDT improves impedance matching and field continuity by smoothing the dielectric-to-free-space transition, thereby alleviating a key bandwidth limitation of conventional combined antennas. Through iterative simulation, low-cost fabrication, and experimental validation, the proposed design achieves a 2.8x bandwidth enhancement, increasing the measured fractional bandwidth from 53% to 148%, with S11 < −10 dB from 0.5 to 3.0 GHz and with an additional −10 dB operating band from 3.5 to 4.4 GHz. Simulations predict a peak gain value of 15 dBi at 2.1 GHz. High-voltage pulsed tests (9–10 kV, 500 ps rise time) confirm robust operation, with radiated electric fields exceeding 10 kV/m at 1 m and no observable breakdown. The lightweight 3D-printed PLA structure (197 g) provides a scalable solution for directed-energy and electromagnetic-pulse applications. Full article

With the continuous advancement of display technology and advanced integrated circuits, oxide thin-film transistors (TFTs) have become core devices due to their high mobility, low leakage current and excellent large-area uniformity. To achieve low power consumption, high performance and high reliability, the introduction of high-k gate insulating layers is crucial. Among the numerous high-k materials, hafnium oxide (HfO₂) has attracted significant attention due to its excellent dielectric properties and good compatibility with CMOS processes. In this paper, uniform and dense HfO₂ films were successfully fabricated using the sol–gel method to serve as insulating layers for TFT devices. Through experimental analysis, 400 °C was determined to be the optimal annealing temperature. At this temperature, the effects of replacing SiO₂ with HfO₂ as the insulating layer, as well as the impact of reducing film thickness, on TFT devices were investigated. Ultimately, at an annealing temperature of 400 °C, an 85 nm-thick HfO₂ film achieved the highest on/off current ratio (I_on/off = 1.11 × 10⁶), the lowest subthreshold swing (SS = 0.53 V/dec), the lowest threshold voltage (Vth = −1.1 V) and the lowest off-current ratio (I_off = 2.5 × 10⁻¹² A). It was confirmed that replacing SiO₂ with HfO₂ as the insulating layer is a viable approach for reducing the volume of TFT devices. Full article

The structural, mechanical, electronic, and optical properties of cubic double perovskite oxides A₂TiSiO₆ (A = Ca, Sr, Ba) were systematically investigated using first-principles density functional theory calculations. Structural optimization within the GGA–PBE framework confirms that all compounds crystallize in a stable cubic phase. The negative formation energies indicate thermodynamic stability and potential experimental synthesizability. Ab initio molecular dynamics (AIMD) simulations performed at 300 K further confirm the dynamical stability of all compounds under finite-temperature conditions. The Born–Huang stability criteria performed elastic constant analysis establishes mechanical stability and the derived mechanical moduli indicate the presence of rigid but brittle behavior with moderate amounts of elastic anisotropy. Calculation of the electronic band structure reveals that all the compounds are direct wide-bandgap semiconductors, with the HSE06 bandgaps of Ca₂TiSiO₆, Sr₂TiSiO₆ as well as Ba₂TiSiO₆ being 2.61, 2.50 and 2.37 eV, respectively. The optical property analysis has shown that they are strong in terms of their absorption in the visible–ultraviolet region, with high dielectric constants and good refractive indices, which makes them appropriate in optoelectronics and photovoltaic applications. On the whole, A₂TiSiO₆ double perovskites are promising for use as wide-bandgap materials in the development of superior optoelectronic devices. Full article

In MOSFETs, mobility enhancement is a key factor for improving the electrical performance and enabling their use in new applications, such as low-power, digital, and medical applications. This mobility improvement can be technically achieved by using different techniques that exploit the complex behavior of mobility (Coulomb, phonon, and surface roughness mobilities). Previous reviews have primarily focused on two main technologies: the introduction of mechanical stress and crystallographic orientation. Therefore, this review summarizes all key techniques that can enhance mobility, and each of these techniques is linked to a physical origin. Mechanical stress notably affects phonon mobility, whereas silicon thickness and channel impurities mainly affect the Coulomb mobility. Moreover, the dielectric oxide type, heat treatments, surface cleaning, ionic implantation in the oxide, and oxynitrides affect surface roughness mobility. In addition, the crystallographic orientation affects Coulomb, phonon, and surface roughness mobilities. Furthermore, the study of the series resistance engineering also affects the performance. Therefore, the simultaneous use of multiple of these techniques leads to an enhancement of the effective mobility at low, medium, and high effective electric fields, and the combined effect results in a more significant mobility increase. Full article