High Dielectric Constant Properties Research Articles

MOF-derived ZnCo2O4 @ Ti3C2TX nanosheet with high microwave absorption

Abstract Electromagnetic wave absorbing (EWA) materials have a wide application in military technology, so it is necessary to develop EWA materials with lightweight, and wide absorption bandwidth and strong absorption. Novel two-dimensional material (MXene) with high dielectric constant property and unique structure has attracted extensive focus in microwave absorption. However, the high conductivity of MXene limits its application in microwave absorption. In this work, ZnCO2O4 nanoparticles were obtained via a hydrothermal method and subsequent heat treatment. Then it was anchored on MXene nanosheets. The effective absorption bandwidth (EAB) of the ZnCO2O4@Ti3C2Tx is 4.77GHz at 1.5mm thickness. Composites show great potential in the field of designing a new generation of efficient and lightweight microwave absorbers, which are expected to be used in various EWA applications.

Glass fiber strengthened BNNS/ST/polyolefin composites with high dielectric constant and high thermal conductivity

The present research presents an examination of the consequential effects brought about by the introduction of short-cut E-glass fibers (GF) on the properties of high-dielectric constant, high-thermal conductivity microwave composite systems (xGF/(8-x)BNNS/78 wt%ST/polyolefin, x = 0-8 wt%, BNNS: hexagonal boron nitride nanosheets). The GF is modified using KH550, with the success of the surface modification definitively confirmed by X-ray Photoelectron Spectroscopy (XPS) and Fourier Transform infrared spectroscopy (FTIR). All components are found to exhibit consistently ultra-high and stable dielectric constants within the 8–12 GHz frequency range (Dk = 17.7–18.08). Based on thermogravimetry analysis (TGA) and dynamic mechanical analysis (DMA) results, the incorporation of modified GF improve the thermal stability of the composite materials, enhancing thermal decomposition temperature, residual carbon content and glass transition temperature. Furthermore, replacing BNNS with GF significantly amplifies the mechanical properties of the composite substrate. This substitution leads to a notable reduction in the coefficient of thermal expansion (CTE) in all directions while simultaneously increasing the bending and tensile strength. At the same time, the composites can maintain reasonably high thermal conductivity values. Overall, with a GF concentration of 4 wt%, the composite showcases an appreciable increase in dielectric constants (17.81), a high thermal conductivity (1.3 W/m·K) and enhances mechanical properties (cross-plane CTE: 15.44 μm/(m·°C), in-plane CTE: 26.06 μm/(m·°C), bending strength: 65.6 MPa, tensile strength: 17.42 MPa). Considering its superior performance metrics, the composite can be identified as an optimal choice for microwave composite dielectric substrate material.

Solution processed rare-earth doped high-k dielectrics for low-power IGZO transistors

Low-power metal oxide transistors are highly required in displays, logic circuit and sensors. High quality gate dielectrics with the properties of high dielectric constant, smooth surface, and excellent insulating performance are critical to realize the above mentioned transistors. In this work, we present a universal strategy by using rare-earth (RE) elements (Y, Er and Yb) as dopants to improve the dielectric properties of zirconia film for low-power transistors. Additionally, all the dielectric films are prepared by solution process, which is compatible with low-cost and large-area manufacturing technology. The leakage current densities of zirconia films decrease from 1.27 × 10−5 A/cm2 to 2.8 × 10−7 A/cm2, 6.6 × 10 − 7 A/cm2, and 4.3 × 10−7 A/cm2 by doping a small amount of Y, Er, and Yb in zirconia films, respectively. Furthermore, bottom-gate top-contact indium-gallium-zinc oxide (IGZO) transistors with RE-doped zirconia dielectrics show one order improved current on/off (∼104) ratio and achieve one order improvement in mobility (3.11, 2.85, 2.75 cm2V−1S−1 for Y-, Er-, Yb-doped devices respectively) compared with that of pure zirconia film based devices (0.30 cm2V−1S−1). Moreover, the subthreshold swing (SS) of TFTs based on RE-doped and undoped ZrO2 dielectric films are calculated (0.2, 0.36, 0.21 V/dec for Y-, Er-, Yb-doped devices respectively, and 0.51 V/dec for undoped devices) This study demonstrates the validity of RE ions as dopants in gate dielectrics to achieve high-performance low-power metal oxide transistors.

Fabrication of Lead-free (K0.5Na0.5)1−xAg x NbO3 Ferroelectric Ceramics and Their Dielectric Properties

In this study, lead-free (K0.5Na0.5)1−xAg x NbO3 (x = 0.00, 0.10, 0.15, 0.20, 0.25, and 0.30) ferroelectric ceramics were fabricated using solid-state synthesis without A-site and B-site manufacturing step. The (K0.5Na0.5)1−xAg x NbO3 ceramics were sintered at 1110 °C for 4 h after calcination at 800 °C for 3 h. The sintered sample was dense, and the grain size was 1.02 ~ 7.8 μm. For x ≤ 0.2, the sintered ceramic samples had a single perovskite structure. The temperature dependence of the dielectric constant in the (K0.5Na0.5)1−xAg x NbO3 was measured at 1 kHz using an LCR meter. The high dielectric constant properties could be obtained in (K0.5Na0.5)1−xAg x NbO3 ceramics. The orthorhombic-to-tetragonal phase transition temperature and ferroelectric Curie temperature decreased linearly with increasing mole fraction of the Ag content. The Curie temperature shifted from 393 °C for (K0.5Na0.5)NbO3 ceramics to 317 °C for (K0.5Na0.5)0.7Ag0.3NbO3 ceramics. The maximum dielectric constant was 8930 at 330 °C in the (K0.5Na0.5)0.8Ag0.2NbO3 ceramics.

Isolation of Chromium(VI) from Aqueous Solution by Electromembrane Extraction

ABSTRACTElectromembrane extraction (EME) is a powerful extraction and preconcentration technique for ionizable species. However, the ionic contents in the sample can influence the extraction efficiency and system stability due to electrolysis. In this work, the electromembrane extraction of chromium(VI) was developed using various levels of ionic samples. 2-Nitrophenyl octyl ether was the most suitable supported liquid membrane that delayed the electrolytic occurrence of air bubbles at the electrodes due to its high viscosity and high dielectric constant properties. The electromembrane extraction method was optimized using 5 mM NaCl (630 µS cm−1); the applied potential was 100 V and the extraction time was 15 min. The enrichment factor of 80 was obtained over a linear working range of 10.0–80.0 µg L−1. The method performance was tested using mineral water, drinking water, tap water, and surface water. The method recoveries based on matrix-matched calibration were 95–125% with standard deviations within 15%.

Recent progress in the synthesis of hybrid halide perovskite single crystals

Hybrid halide perovskite based solar cells have demonstrated unprecedented progress in their efficiency, leading to efficiencies of up to 22.1%, in the past six years. Moreover, their intriguing properties of high dielectric constant, wide optical absorption range, low trap density, low non-radiative recombination and photoluminescence have attracted great research interest in the fields of optoelectronic applications and photovoltaics. This review briefly outlines the frontier of the research fields of perovskite materials, and summarizes the structure and growth of hybrid perovskite single crystals. Finally, the enormous challenges and the promising outlook of these active topics are highlighted.

Dielectric properties of continuous composition spreaded MgO–Ta2O5 thin films

The dielectric properties of MgO–Ta2O5 continuous composition spread (CCS) thin films were investigated. The MgO–Ta2O5 CCS thin films were deposited on Pt/Ti/SiO2/Si substrates by off-Axis RF magnetron sputtering system, and then the films were annealed at 350°C with rapid thermal annealing system in vacuum. The dielectric constant and loss of MgO–Ta2O5 CCS thin films were plotted via 1500 micron-step measuring. The specific point of Ta2O5–MgO CCS thin film (post annealed at 350°C) showing superior dielectric properties of high dielectric constant (k∼28) and low dielectric loss (tanδ<0⋅004) at 1MHz were found in the area of 3–5mm apart from Ta2O5 side on the substrate. The cation's composition of thin film was Mg:Ta=0.4:2at%.

Electrical properties of high permittivity ZrO2 gate dielectrics on strained-Si

Deposition and electrical properties of high dielectric constant (high-k) ultrathin ZrO2 films on tensilely strained silicon (strained-Si) substrate are reported. ZrO2 thin films have been deposited using a microwave plasma enhanced chemical vapor deposition technique at a low temperature (150 °C). Metal insulator semiconductor (MIS) structures are used for high frequency capacitance–voltage (C–V), current–voltage (I–V), and conductance–voltage (G–V) characterization. Using MIS capacitor structures, the reliability and the leakage current characteristics have been studied both at room and high temperature. Schottky conduction mechanism is found to dominate the current conduction at a high temperature. Observed good electrical and reliability properties suggest the suitability of deposited ZrO2 thin films as an alternative as gate dielectrics. Compatibility of ZrO2 as a gate dielectric on strained-Si is shown.

Electrical properties of ZrO 2 films on Si 1− x− yGe xC y epitaxial layers

Deposition and electrical properties of high dielectric constant (high- k) ultrathin ZrO 2 films on partially strain-compensated Si 1− x− y Ge x C y /n-Si substrates are reported. Metal insulator semiconductor (MIS) structures were used for high frequency capacitance–voltage ( C– V), current–voltage ( I– V), and Fowler-Nordheim (F-N) constant current stressing studies.

The effect of PbO loss on microwave dielectric properties of (Pb,Ca)(Zr,Ti)O 3 ceramics

(Pb 1−x,Ca x)(Zr 1−y,Ti y)O 3 (PCZT) perovskite type ceramics exhibit microwave dielectric properties of high dielectric constant (ε r), high unloaded Q and small temperature coefficient of resonant frequency (τ f). However, the sintering temperature was as high as 1450°C and the microstructure and dielectric properties were difficult to control due to high PbO volatility. In this paper, we report the effect of PbO loss on microstructure and microwave dielectric properties of PCZT ceramics. Suppression of PbO loss by B-site ion substitution in PCZT was also investigated.

Boundary Analysis Of SrTio3 Ceramic Condenser

SrTiO3-based semiconducting ceramics are widely used to electric devices such as dielectric condensers and varistors due to their properties of high dielectric constant, high dispersion frequency and small temperature dependence of the dielectric constant. The electric properties of these ceramic devices have been studied and found to be deeply influenced by the crystal growth mechanism, the grain boundary layer characteristics and the sintering atmosphere that is represented by such factors as oxygen partial pressure and processing temperature which relate to the atom vacancy formation. Atom vacancies, which play an important role to the electrical properties, have been detected by cathodoluminescence (CL) spectroscopy with scanning electron microscopy (SEM).A ceramic condenser (Sr0.94Ca0.05Ba0.01)0.99TiO3 was investigated by Hitomi el at: using transmission electron microscopy (TEM). The material is a boundary layer (BL) semiconducting ceramic condenser, having dielectric layers between semiconducting grains. The same condenser material was investigated in this report at the grain boundary region using high resolution (scanning) transmission electron microscope (TEMSTEM) capable of High Angle Annular Dark Field (HAADF) technique.