Current development, optimisation strategies and future perspectives for lead-free dielectric ceramics in high field and high energy density capacitors.

To meet the United Nations' sustainable development goal of affordable and clean energy, there has been a growing need for low-cost, green, and safe energy storage technologies. High-field and energy-density capacitors have gained substantial attention from academics and industry, particularly for power electronics, where they will play a key role in optimising the performance of management systems in electric vehicles. The key figure of merit, energy density (), for high-field applications has dramatically increased year-on-year from 2020 to 2024, as evidenced by over 250 papers, demonstrating ever larger values.

Aqueous Cold Sintering of Li-Based Compounds.

Aqueous cold sintering of two lithium-based compounds, the electrolyte LiLaZrAlO (LLZAO) and cathode material LiCoO (LCO), is reported. For LLZAO, a relative density of ∼87% was achieved, whereas LCO was sintered to ∼95% with 20 wt % LLZAO as a flux/binder. As-cold sintered LLZAO exhibited a low total conductivity (10 S/cm) attributed to an insulating grain boundary blocking layer of LiCO.

Novel Method to Achieve Temperature-Stable Microwave Dielectric Ceramics: A Case in the Fergusonite-Structured NdNbO System.

Microwave dielectric ceramics with permittivity (ε) ∼ 20 play an important role in massive multiple-input multiple-output (MIMO) technology in 5G. Although fergusonite-structured materials with low dielectric loss are good candidates for 5G application, tuning the temperature coefficient of resonant frequency (TCF) remains a problem. In the present work, smaller V ions ( = 0.

Dynamic tilting in perovskites.

A new computational analysis of tilt behaviour in perovskites is presented. This includes the development of a computational program - PALAMEDES - to extract tilt angles and the tilt phase from molecular dynamics simulations. The results are used to generate simulated selected-area electron and neutron diffraction patterns which are compared with experimental patterns for CaTiO.

Electroceramics for High-Energy Density Capacitors: Current Status and Future Perspectives.

Materials exhibiting high energy/power density are currently needed to meet the growing demand of portable electronics, electric vehicles and large-scale energy storage devices. The highest energy densities are achieved for fuel cells, batteries, and supercapacitors, but conventional dielectric capacitors are receiving increased attention for pulsed power applications due to their high power density and their fast charge-discharge speed. The key to high energy density in dielectric capacitors is a large maximum but small remanent (zero in the case of linear dielectrics) polarization and a high electric breakdown strength.

Novel BaTiO-Based, Ag/Pd-Compatible Lead-Free Relaxors with Superior Energy Storage Performance.

Ceramic dielectrics are reported with superior energy storage performance for applications, such as power electronics in electrical vehicles. A recoverable energy density () of ∼4.55 J cm with η ∼ 90% is achieved in lead-free relaxor BaTiO-0.

Towards revealing key factors in mechanical instability of bioabsorbable Zn-based alloys for intended vascular stenting.

Zn-based alloys are recognized as promising bioabsorbable materials for cardiovascular stents, due to their biocompatibility and favorable degradability as compared to Mg. However, both low strength and intrinsic mechanical instability arising from a strong strain rate sensitivity and strain softening behavior make development of Zn alloys challenging for stent applications. In this study, we developed binary Zn-4.

Temperature Stable Cold Sintered (BiLi)(VMo)O-NaMoO Microwave Dielectric Composites.

Dense (BiLi)(VMo)O-NaMoO (100-x) wt.% (BiLi)(VMo)O (BLVMO)-x wt.% NaMoO (NMO) composite ceramics were successfully fabricated through cold sintering at 150 °C under at 200 MPa for 30 min.

Growth of BiFeO thin films by chemical solution deposition: the role of electrodes.

BiFeO (BFO) thin films were grown by chemical solution deposition on a range of electrodes to determine their role in controlling the phase formation and microstructure of the films. The crystallization on oxide electrodes followed the sequence: amorphous → BiO(CO) → perovskite, while those on Pt crystallized directly from the amorphous phase. IrO electrodes promoted perovskite phase formation at the lowest temperature and LaNiO additionally induced local epitaxial growth.

Nanoscale Mapping of Bromide Segregation on the Cross Sections of Complex Hybrid Perovskite Photovoltaic Films Using Secondary Electron Hyperspectral Imaging in a Scanning Electron Microscope.

Mixed halide (I/Br) complex organic/inorganic hybrid perovskite materials have attracted much attention recently because of their excellent photovoltaic properties. Although it has been proposed that their stability is linked to the chemical inhomogeneity of I/Br, no direct proof has been offered to date. Here, we report a new method, secondary electron hyperspectral imaging (SEHI), which allows direct imaging of the local variation in Br concentration in mixed halide (I/Br) organic/inorganic hybrid perovskites on a nanometric scale.

Synthesis of Barium Titanate Using Deep Eutectic Solvents.

Novel synthetic routes to prepare functional oxides at lower temperatures are an increasingly important area of research. Many of these synthetic routes, however, use water as the solvent and rely on dissolution of the precursors, precluding their use with, for example, titanates. Here we present a low-cost solvent system as a means to rapidly create phase-pure ferroelectric barium titanate using a choline chloride-malonic acid deep eutectic solvent.

Crystal Structure, Infrared Spectra, and Microwave Dielectric Properties of Temperature-Stable Zircon-Type (Y,Bi)VO Solid-Solution Ceramics.

A series of (Bi Y )VO (0.4 ≤ ≤ 1.0) ceramics were synthesized using the traditional solid-state reaction method.

Stabilisation of Fe2O3-rich Perovskite Nanophase in Epitaxial Rare-earth Doped BiFeO3 Films.

Researchers have demonstrated that BiFeO3 exhibits ferroelectric hysteresis but none have shown a strong ferromagnetic response in either bulk or thin film without significant structural or compositional modification. When remanent magnetisations are observed in BiFeO3 based thin films, iron oxide second phases are often detected. Using aberration-corrected scanning transmission electron microscopy, atomic resolution electron energy loss spectrum-mapping and quantitative energy dispersive X-ray spectroscopy analysis, we reveal the existence of a new Fe2O3-rich perovskite nanophase, with an approximate formula (Fe0.

Unveiling the Role of CNTs in the Phase Formation of One-Dimensional Ferroelectrics.

Carbon nanotubes (CNTs) have the potential to act as templates or bottom electrodes for three-dimensional (3D) capacitor arrays, which utilize one-dimensional (1D) ferroelectric nanostructures to increase the memory size and density. However, growing a ferroelectric on the surface of CNTs is nontrivial. Here, we demonstrate that multiwalled (MW) CNTs decrease the time and temperature for the formation of lead zirconium titanate Pb(Zr1-xTix)O3 (PZT) by ∼100 °C commensurate with a decrease in activation energy from 68 ± 15 to 27 ± 2 kJ/mol.

The osteogenic response of mesenchymal stromal cells to strontium-substituted bioactive glasses.

Bioactive glasses are known to stimulate bone healing, and the incorporation of strontium has the potential to increase their potency. In this study, calcium oxide in the 45S5 bioactive glass composition was partially (50%, Sr50) or fully (100%, Sr100) substituted with strontium oxide on a molar basis. The effects of the substitution on bioactive glass properties were studied, including density, solubility, and in vitro cytotoxicity.

A family of oxide ion conductors based on the ferroelectric perovskite Na0.5Bi0.5TiO3.

Oxide ion conductors find important technical applications in electrochemical devices such as solid-oxide fuel cells (SOFCs), oxygen separation membranes and sensors. Na0.5Bi0.

Determination of relative in vivo osteoconductivity of modified potassium fluorrichterite glass-ceramics compared with 45S5 bioglass.

Potassium fluorrichterite (KNaCaMg(5)Si(8)O(22)F(2)) glass-ceramics were modified by either increasing the concentration of calcium (GC5) or by the addition of P(2)O(5) (GP2). Rods (2 × 4 mm) of stoichiometric fluorrichterite (GST), modified compositions (GC5 and GP2) and 45S5 bioglass, which was used as the reference material, were prepared using a conventional lost-wax technique. Osteoconductivity was investigated by implantation into healing defects in the midshaft of rabbit femora.

In vitro biocompatibility of modified potassium fluorrichterite and potassium fluorrichterite-fluorapatite glass-ceramics.

Potassium fluorrichterite (KNaCaMg(5)Si(8)O(22)F(2)) glass-ceramics were modified by either increasing the concentration of calcium in the glass (GC5), or by the addition of P(2)O(5) to produce potassium fluorrichterite-fluorapatite (GP2). The solubility of the stoichiometric composition (GST), GC5 and GP2 were measured using the standard test described in ISO 6872:1995 (Dental Ceramics). Ion release profiles were determined for Si, Ca, Mg, Na, K and P using inductively coupled plasma mass spectrometry and fluoride ion (F(-)) concentration was measured using an ion-selective electrode.

Prediction of osteoconductive activity of modified potassium fluorrichterite glass-ceramics by immersion in simulated body fluid.

Potassium fluorrichterite (KNaCaMg(5)Si(8)O(22)F(2)) glass-ceramics were modified by either increasing the concentration of calcium (GC5) or by the addition of P(2)O(5) (GP2). The stoichiometric composition (GST), GC5 and GP2 were soaked in simulated body fluid (SBF) along with 45S5-type bioglass as a control. After immersion, surface analyses were performed using thin-film X-ray diffraction (TF-XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and Fourier-transform infrared (reflection) spectroscopy (FT-IR).

The effect of investment materials on the surface of cast fluorcanasite glasses and glass-ceramics.

Modified fluorcanasite glass-ceramics were produced by controlled two stage heat-treatment of as-cast glasses. Castability was determined using a spiral castability test and the lost-wax method. Specimens were cast into moulds formed from gypsum and phosphate bonded investments to observe their effect on the casting process, surface roughness, surface composition and biocompatibility.

Electron diffraction of tilted perovskites.

Simulations of electron diffraction patterns for each of the known perovskite tilt systems have been performed. The conditions for the appearance of superlattice reflections arising from rotations of the octahedra are modified to take into account the effects of different tilt systems for kinematical diffraction. The use of selected-area electron diffraction as a tool for perovskite structure determination is reviewed and examples are included.