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Electrostatic energy storage capacitors are essential passive components for power electronics and prioritize dielectric ceramics over polymer counterparts due to their potential to operate more reliably at > 100 ˚C. Most work has focused on non‐linear dielectrics compositions in which polarization (P)/electric displacement (D) and maximum field (Emax) are optimized to give values of energy density, 6≤U≤21 J cm−3. In each case however, either saturation (dP/dE = 0, AFE) or "partial" saturation (dP/dE → 0, RFE) of P limits the value of U which can be achieved before breakdown. It is proposed that U can be further improved with respect to relaxors (RFEs) and anti‐ferroelectrics (AFEs) by designing high permittivity quasi‐linear dielectric (QLD) behaviour in which dP/dE remains constant up to ultrahigh Emax. QLD multilayer capacitor prototypes with dielectric layers composed of 0.88NaNb0.9Ta0.1O3‐0.10SrTiO3‐0.02La(Mg1/2Ti1/2)O3 deliver room temperature U ≈ 43.5 J cm−3, supporting an extremely‐large Emax ≈ 280 MV m−1, both of which exceed current state‐of‐art by a factor of two for devices based on powder, tape‐cast technology. Importantly QLD capacitors exhibit scant variation in U (≈15 J cm−3) up to > 200 ˚C and robust resistance to cyclic degradation, offering a promising new approach for the development of sustainable technology. [ABSTRACT FROM AUTHOR]

In this Letter, low-temperature (400 °C) chemical vapor deposition-grown boron nitride (BN) was investigated as the gate dielectric for AlGaN/GaN metal–insulator–semiconductor high electron mobility transistors (MISHEMTs) on a Si substrate. Comprehensive characterizations using x-ray photoelectron spectroscopy, reflection electron energy loss spectroscopy, atomic force microscope, high-resolution transmission electron microscopy, and time-of-flight secondary ion mass spectrometry were conducted to analyze the deposited BN dielectric. Compared with conventional Schottky-gate HEMTs, the MISHEMTs exhibited significantly enhanced performance with 3 orders of magnitude lower reverse gate leakage current, a lower off-state current of 1 × 10−7 mA/mm, a higher on/off current ratio of 108, and lower on-resistance of 5.40 Ω mm. The frequency-dependent conductance measurement was performed to analyze the BN/HEMT interface, unveiling a low interface trap state density (Dit) on the order of 5 × 1011–6 × 1011 cm−2 eV−1. This work shows the effectiveness of low-temperature BN dielectrics and their potential for advancing GaN MISHEMTs toward high-performance power and RF electronics applications. [ABSTRACT FROM AUTHOR]

GaN metal–insulator–semiconductor high electron mobility transistors (MIS-HEMTs) with scandium aluminum nitride Sc0.2Al0.8N/SiNX composite gate dielectric were demonstrated with improved device performance in terms of current density, on-resistance, breakdown voltage, gate leakage, and current collapse. GaN MIS-HEMTs with single-layer Sc0.2Al0.8N or SiNX were also fabricated as reference. Notably, the current collapse was reduced from ∼38.8% in GaN MIS-HEMTs with single-layer SiNX dielectric to ∼4.9% in the device with composite gate dielectric. The insertion of the thin SiNX layer can mitigate the surface damage due to the ScAlN sputtering process and significantly reduce the interface state density. Furthermore, the high valence band offset of Sc0.2Al0.8N/SiNX of 0.78 eV also plays a key role in the suppression of hole injection and gate leakage current. This work shows the effectiveness of the Sc0.2Al0.8N/SiNX composite gate dielectric and can serve as an important reference for future developments of high-performance reliable GaN HEMTs for power and RF electronics. [ABSTRACT FROM AUTHOR]

Due to their responsiveness to modulation by external direct current fields, dielectric tunable materials are extensively utilized in integrated components, such as ferroelectric phase shifters. Barium strontium titanate ceramics have been considered the most potential tunable materials for a long time. However, the significant dielectric loss and high voltage drive have limited their further applications. Recently, Bi6Ti5WO22 ceramic has regained attention for its high dielectric tunability with low loss. In this study, we judiciously introduce Nb5+ with a larger ionic radius, replacing Ti4+ and W6+. This successful substitution enables the modulation of the phase transition temperature of Bi6Ti5WO22 ceramics to room temperature, resulting in superior tunable properties. Specifically, the 0.7Bi6Ti5WO22−0.3Bi6Ti4Nb2O22 ceramics exhibit giant tunability (~75.6%) with ultralow loss (<0.002) under a low electric field (1.5 kV/mm). This tunability is twice that of barium strontium titanate ceramics with a similar dielectric constant and only one-tenth of the loss. Neutron powder diffraction and transmission-electron-microscopy illustrate the nanodomains and micro-strains influenced by ion substitution. Density functional theory simulation calculations reveal the contribution of ion substitution to polarization. The research provides an ideal substitute for tunable material and a general strategy for adjusting phase transition temperature to improve dielectric properties. The authors realize composite optimization in dielectric tunable materials by simultaneously achieving low electric field, large tunability, and low loss through ion substitution design in ferroelectric tunable materials. [ABSTRACT FROM AUTHOR]

The dielectric properties of asphalt mixture are crucial for future electrified road (e-road) and pavement non-destructive detection. Few investigations have been conducted on the temperature and frequency influencing the dielectric properties of asphalt pavement materials. The development of e-road requires more accurate prediction models of pavement dielectric properties. To quantify the influence of temperature and frequency on the dielectric properties of asphalt mixtures, the dielectric constants, dielectric loss factor and dielectric loss tangents of aggregate, asphalt binders and asphalt mixtures were tested over the temperature range of −30 to 60°C and frequency range of 200 to 2 000 000 Hz. The results showed that the dielectric constants and dielectric loss factors of aggregate, asphalt binders and asphalt mixtures vary linearly with temperature, while the growth rates vary with the frequency. A model based on nonlinear fitting was first presented to estimate the dielectric loss factor, and another prediction model of the dielectric constant of asphalt mixtures considering the temperature impact was proposed afterwards. Compared with classical models, the average relative error of the proposed model of the dielectric constant is the smallest and is less sensitive to the asphalt mixture. This investigation can cast light on the utilization of non-destructive pavement testing and is potentially valuable for e-road using the electromagnetic properties of asphalt pavement materials. This article is part of the theme issue 'Artificial intelligence in failure analysis of transportation infrastructure and materials'. [ABSTRACT FROM AUTHOR]

In this paper, a novel scheme for source/drain-first (S/D-first) full bottom dielectric isolation (BDI), i.e., Full BDI_Last, with integration of a sacrificial Si0.5Ge0.5 layer was proposed and demonstrated in a stacked Si nanosheet gate-all-around (NS-GAA) device structure using TCAD simulations. The proposed full BDI scheme flow is compatible with the main process flow of NS-GAA transistor fabrication and provides a large window for process fluctuations, such as the thickness of the S/D recess. It is an ingenious solution to insert the dielectric material under the source, drain and gate regions to remove the parasitic channel. Moreover, because the S/D-first scheme decreases the problem of high-quality S/D epitaxy, the innovative fabrication scheme introduces full BDI formation after S/D epitaxy to mitigate the difficulty of providing stress engineering in the full BDI formation before S/D epitaxy (Full BDI_First). The electrical performance of Full BDI_Last is demonstrated by a 4.78-fold increase in the drive current compared to Full BDI_First. Furthermore, compared to traditional punch through stoppers (PTSs), the proposed Full BDI_Last technology could potentially provide an improved short channel behavior and good immunity against parasitic gate capacitance in NS-GAA devices. For the assessed inverter ring oscillator (RO), applying the Full BDI_Last scheme allows the operating speed to be increased by 15.2% and 6.2% at the same power, or alternatively enables an 18.9% and 6.8% lower power consumption at the same speed compared with the PTS and Full BDI_First schemes, respectively. The observations confirm that the novel Full BDI_Last scheme incorporated into an NS-GAA device can be utilized to enable superior characteristics to benefit the performance of integrated circuits. [ABSTRACT FROM AUTHOR]

In this work, novel (1 − x)(0.75Na 0. 5 Bi 0. 5 TiO3)-0.25Sr(Zr 0. 2 Sn 0. 2 Hf 0. 2 Ti 0. 2 Nb 0. 2 )O3- x NaNbO3 (NBT-SZSHTN- x NN, x = 0.1, 0.15, 0.2, 0.25) ceramics were fabricated. The influence of co-doping of NN and high entropy perovskite oxide (SZSHTN) on the phase structure, microstructure and dielectric properties of NBT-based lead-free ceramics was investigated. Dense microstructure with a grain size of ∼ 5 μ m is observed. When x = 0.25, a wide dielectric temperature stable range of −35.4–224.3 ∘ C with a low temperature coefficient of capacitance of < 10% is achieved, fulfilling the industry standard of Y9P specification. Furthermore, excellent energy storage performance with recoverable energy density of 2.4 J/cm3, discharge efficiency of 71%, power density of 25.495 MW/cm3 and discharge rate < 200 ns are simultaneously obtained, which shows great potential for high temperature capacitor applications. [ABSTRACT FROM AUTHOR]

It is difficult to get pure‐phase Mg3B2O6 (abbreviated as MBO) ceramics by the traditional high‐temperature solid‐state reaction method. In this paper, pure‐phase MBO ceramics were successfully densified and obtained by combining the cold sintering and post‐annealing process. The relative density of MBO ceramics was ∼80% cold sintered at 150°C/90 min/800 MPa, which was further improved to ∼91% by post‐annealing at 900°C, 400°C lower than that of the traditional high‐temperature sintering process (∼1300°C). X‐ray powder diffraction (XRD), scanning electron microscopy (SEM), and Raman results demonstrated that the secondary phase of MgO was effectively eliminated, and dense microstructure was observed by the cold‐sintering process plus post‐annealing treatment. Finally, the microwave dielectric properties of MBO were evaluated with εr: 5.15–6.37, Q×f: 5942–16 686 GHz, τf: −48.45–69.72 ppm/°C. [ABSTRACT FROM AUTHOR]

In this study, a high‐entropy perovskite oxide Sr(Zr0.2Sn0.2Hf0.2Ti0.2Nb0.2)O3 (SZSHTN) was first introduced to Na0.5Bi0.5TiO3 (NBT) lead‐free ferroelectric ceramics to boost both the high‐temperature dielectric stability and energy storage performance. Excellent comprehensive performance was simultaneously obtained in the 0.8NBT–0.2SZSHTN ceramic with high ε′ value (> 2000), wide ε′‐temperature stable range (TCC < 5%, 52.4–362°C), low tanδ value in a wide range (<0.01, 90–341°C) and high energy storage performance (Wrec = 3.52 J/cm3, Wrec and η varies ±6.08% and ±7.4% from 20 to 150°C), which endows it the promising potential to be used in high‐temperature environments. [ABSTRACT FROM AUTHOR]

Layered perovskite structured Re5Ti4CrO17 (Re = La, Nd) ceramics were synthesized via a sol–gel method. Rietveld analysis and Raman spectroscopy showed that the samples crystallize into an orthorhombic crystal structure with the space group Pmnn. The samples showed a dense and homogeneous microstructure when sintered at 1600 °C for 4 h and the grain size was found to be 2.64–4.93 μm. La5Ti4CrO17 and Nd5Ti4CrO17 exhibited dielectric constant (εr) ~ 23 and 12 at 1 MHz, respectively, which was dependent on the dielectric polarizability and bond lengths. Dielectric loss at room temperature was found to be ≤ 0.05 (at 1 MHz) for La5Ti4CrO17 and Nd5Ti4CrO17, respectively. Furthermore, magnetic study of the samples showed a paramagnetic behavior. [ABSTRACT FROM AUTHOR]

Gehlenite‐type Ca2Al2SiO7 ceramics were prepared by the conventional solid‐state reaction. Two anomalies were found in the plot of dielectric constant vs temperature, which were associated with space charge polarization. Pure phase crystal structure and no phase transition were observed in the temperature‐dependent X‐ray diffraction (XRD) patterns and Raman spectra from room temperature (RT) to 900°C. There was relevant relation between Q × f and τƒ with the stretching vibrations of Ca‐O bond and O‐Ca‐O bending in CaO8 polyhedron. Excellent microwave dielectric properties (εr = 8.86, Q × f = 22 457 GHz, and τf = −51.06 ppm/°C) were obtained for Ca2Al2SiO7 sintered at 1440°C in air, which had the potential application to use in microwave and millimeter‐wave devices such as capacitors and substrates. [ABSTRACT FROM AUTHOR]

Lead-based electroceramics such as Pb(Zr.Ti)O3 (PZT) and its derivatives have excellent piezoelectric, pyroelectric and energy storage properties and can be used in a wide range of applications. Potential lead-free replacements for PZT such as potassium sodium niobate (KNN) and sodium bismuth titanate (NBT) have a much more limited range of useful properties and have been optimized primarily for piezoelectric applications. Here, we review the initial results on a new generation of lead-free electroceramics based on BiFeO3-BaTiO3 (BF-BT) highlighting the essential crystal chemistry that permits a wide range of functional properties. We demonstrate that with the appropriate dopants and heat treatment, BF-BT can be used to fabricate commercially viable ceramics for applications, ranging from sensors, multilayer actuators, capacitors and high-density energy storage devices. We also assess the potential of BF-BT-based ceramics for electrocaloric and pyroelectric applications. [ABSTRACT FROM AUTHOR]

It has been a challenge to provide a unified description of the dielectric response vs temperature for ferroelectrics with diffuse phase transition (DPT) and relaxor behaviors, which can be used to fit the dielectric response both below and above the peak temperature (Tm). Most of the available functions used in fitting experimental data only provide a description of the dielectric permittivity near and above Tm. In this work, employing a macroscopic and phenomenological statistical model and using Ba(Ti1−x Zrx)O3 ceramics as an example, we revisit the dielectric permittivity's temperature dependence, analyzing their DPT and relaxor behaviors and providing a complete description over the whole temperature range. We show that good agreements between theoretical and experimental results can be achieved. To better understand how Ba(Ti1−x Zrx)O3 ceramics changes from DPT to relaxor with increasing x, we also discuss the relation between the fitting parameters and Ba(Ti1−x Zrx)O3's composition and structure, which suggests that the parameters from the statistical model reflect the size of the correlated Ti ions (small clusters or polar nanoregions), which largely determine the behavior of Ba(Ti1−x Zrx)O3 ceramics. [ABSTRACT FROM AUTHOR]

Nb and Mn were doped, respectively, to 0.8 Pb( Sn0.46 Ti0.54) O3-0.2 Pb( Mg1/3 Nb2/3) O3 ( PST- PMN) to improve electrical properties for meeting the requirement in various fields. The additions of Nb and Mn influence in a pronounced way the structure, and improve the densities of the ceramics. Nb-doped PST- PMN increased the piezoelectric coefficient d33, planar electromechanical coupling kp, and relative dielectric constant ε, indicating 'soft' piezoelectric behavior. Mn doping played a 'hard' part, which significantly enhanced the mechanical quality factor Qm without deteriorating other piezoelectric properties. The most excellent properties of Nb-doped PST- PMN were obtained with doping amount of 0.75 mol%, specifically d33, kp, being on the order of 455 pC/N, 57.5% and 3560, respectively. The addition of 0.75 mol% Mn for PST- PMN presented the optimum electrical properties, with Qm of 554, d33 of 430 pC/N, kp of 57.0%, ε of 2770. It was proposed that the addition of Nb, Mn generated different defect dipoles involved in the domain walls motion and intrinsic piezoelectric responses, leading to different effects on electrical properties. [ABSTRACT FROM AUTHOR]

Abstract: (1− x)Pb(Sn1−y Ti y )O3–xPb(Mg1/3Nb2/3)O3 (x =0.1–0.4, y =0.45–0.65) ternary system was prepared using two-step columbite precursor method. Phase structure of the synthesized ceramics was studied by using X-ray powder diffraction and the morphotropic phase boundary (MPB) curve of the ternary system was confirmed. The isothermal map of Curie temperature (T C) in the phase diagram was obtained based on the dielectric–temperature measurements. The coercive field E C and internal bias field E i were found to increase with increasing PT content, while decrease with increasing PMN content. The optimum properties were achieved in the MPB composition 0.8Pb(Sn0.45Ti0.55)O3–0.2Pb(Mg1/3Nb2/3)O3, with dielectric permittivity ɛ r, piezoelectric coefficient d 33, planar electromechanical coupling k p, mechanical quality factor Q m and T C of being on the order of 3040, 530pC/N, 55.5%, 320 and 190°C, respectively, exhibiting potential usage for high power application. [Copyright &y& Elsevier]

Abstract: yPb(In1/2Nb1/2)O3–(1− x − y)Pb(Mg1/3Nb2/3)O3–xPbTiO3 (yPIN–(1− x − y)PMN–xPT) polycrystalline ceramics with morphotropic phase boundary (MPB) compositions were synthesized using columbite precursor method. X-ray diffraction results indicated that the MPB of PIN–PMN–PT was located around PT=0.33–0.36, confirmed by their respective dielectric, piezoelectric and electromechanical properties. The optimum properties were found for the MPB composition 0.36PIN–0.30PMN–0.34PT, with dielectric permittivity ɛ r of 2970, piezoelectric coefficient d 33 of 450pC/N, planar electromechanical coupling k p of 49%, remanent polarization P r of 31.6μC/cm2 and T C of 245°C. According to the results of dielectric and pyroelectric measurements, the Curie temperature T C and rhombohedral to tetragonal phase transition temperature T R–T were obtained, and the “flat” MPB for PIN–PMN–PT was achieved, indicating that the strongly curved MPB in PMN–PT system was improved by adding PIN component, offering the possibility to grow single crystals with high electromechanical properties and expanded temperature usage range (limited by T R–T). [Copyright &y& Elsevier]

NaNbO 3 (NN)-based dielectric ceramics for energy storage have garnered significant interest due to their high saturation polarization, low residual polarization, and superior breakdown strength (E b). However, the low recoverable energy storage density (W rec) and efficiency (η) significantly limited their practical application. Herein, BiFeO 3 (BF) was incorporated into NN to optimize the energy storage performance. The NN-BF ceramics exhibited pronounced antiferroelectric (AFE) relaxor phase, alongside grain size reduction and E b enhancement, which contributed to a significant increase of W rec and η. Specially, the optimum W rec of 4.43 J/cm³ and η of 71.51 % were achieved at the composition of 0.9NN-0.1BF. Besides, stable energy storage performance was maintained over a wide temperature range (20–120 °C). These results highlight the potential of NN-BF relaxor AFE ceramics as promising candidates for high-performance energy storage applications. [ABSTRACT FROM AUTHOR]

Following increased environmental concerns on the toxicity of lead, the discovery of ultrahigh piezoelectricity in lead-free piezoelectric materials is critical for the substitution of commercial lead zirconate titanate (PZT) ceramics in numerous electronic devices. In this work, a synergistic design strategy is proposed to enhance the piezoelectricity in lead-free piezoelectric materials by flattening the Gibbs free energy density profile, via the coexistence of multiple phases and local structural heterogeneity. This strategic material design approach is based on first-principles calculations combined with Landau phenomenological theory and phase field simulations. Sustainable Stannum-doped BaTiO 3 lead-free ferroelectric ceramics are prepared to validate our proposed mechanism, and a giant piezoelectric coefficient d 33 > 1100 pC/N is achieved, being the highest value reported in lead-free piezoceramics. The mechanism and paradigm of the excellent piezoelectricity achieved here provides a feasible solution for replacing lead-based piezoelectrics by lead-free counterparts. Image 1 • A synergetic design strategy to design novel lead-free piezoelectrics with ultrahigh piezoelectricity. • A giant piezoelectric coefficient d 33 > 1100 pC/N is achieved, being the highest value reported in lead-free piezoceramics. • The mechanism and paradigm provide a feasible solution for lead-free materials of replacing lead-based counterparts. [ABSTRACT FROM AUTHOR]

Focusing on the high resistivity together with low intrinsic conduction in BaTiO 3 –BiMeO 3 materials, it can contribute to the development of reliable high-temperature capacitor materials. In this work, x (Bi 0·5 Li 0.5)TiO 3 -(0.8- x)BaTiO 3 -0.2BiScO 3 (where x ranges from 0 to 0.2) ceramics were fabricated by a solid reaction method. The temperature stability of dielectric permittivity and resistance are improved significantly by the introduce of (Bi 0·5 Li 0.5)TiO 3 (referred to as BL) compared to BaTiO 3 –BiMeO 3. The composition discrepancy due to chemical inhomogeneity can be determined by SEM and EDS mapping although XRD exhibit a single perovskite phase. The characteristics of distinct conductivity behaviors in micro-regions was measured by kelvin probe force microscopy (KPFM). The non-stoichiometry gives rise to two kinds of defects for charge compensation: an ionic compensation and oxygen-vacancy compensation in different grains. The increase of the hopping activation energy of charged carries enhances the high-temperature resistance of the system. The sample of x = 0.15 shows very good temperature stability of dielectric permittivity in the temperature range from 200 °C to 400 °C, and that of x = 0.1 exhibits the highest resistivity of 3.6 MΩ cm at 570 °C. The proposed method gives an efficient strategy for improving the dielectric temperature stability and insulation by the special defect compensation in the perovskite oxides. [ABSTRACT FROM AUTHOR]

Multilayer ceramic capacitors (MLCCs) based on (Bi0.95Li0.05)(V0.9Mo0.1)O4‐Na2Mo2O7 (BLVMO‐NMO), with εr = 39, temperature coefficient of capacitance, TCC ≈ ±0.01%, and tan δ = 0.01 at 1 MHz, are successfully fabricated by a cold‐sintering process at 150 °C. Scanning electron microscopy of the MLCCs combined with EDS mapping, X‐ray diffraction, and Raman spectroscopy reveals well‐laminated and undistorted dielectric layers composed of BLVMO and NMO discrete phases separated by Ag internal electrodes. Prototypes show comparable properties to C0G MLCCs (TCC = ±30 ppm °C−1 from −55 to +125 °C) currently commercially fabricated at 1100 °C using CaZrO3‐based dielectrics with glass sintering aids and Ni internal electrodes. [ABSTRACT FROM AUTHOR]

Dense (Bi0.95Li0.05)(V0.9Mo0.1)O4-Na2Mo2O7 (100−x) wt.% (Bi0.95Li0.05)(V0.9Mo0.1)O4 (BLVMO)-x wt.% Na2Mo2O7 (NMO) composite ceramics were successfully fabricated through cold sintering at 150 °C under at 200 MPa for 30 min. X-ray diffraction, back-scattered scanning electron microscopy, and Raman spectroscopy not only corroborated the coexistence of BLVMO and NMO phases in all samples, but also the absence of parasitic phases and interdiffusion. With increasing NMO concentration, the relative pemittivity (εr) and the Temperature Coefficient of resonant Frequency (TCF) decreased, whereas the Microwave Quality Factor (Qf) increased. Near-zero TCF was measured for BLVMO-20wt.%NMO composites which exhibited εr ~ 40 and Qf ~ 4000 GHz. Finally, a dielectric Graded Radial INdex (GRIN) lens was simulated using the range of εr in the BLVMO-NMO system, which predicted a 70% aperture efficiency at 26 GHz, ideal for 5G applications. [ABSTRACT FROM AUTHOR]

The miniaturization of electronic components has become a megatrend in the future, making colossal dielectric permittivity materials receive unprecedented attention. In this work, we proposed a universal route to achieve colossal dielectric permittivity, low loss factor and excellent dielectric temperature stability in rare earth doped perovskite oxide SrTiO 3. Sm doped SrTiO 3 ceramics prepared by high-energy ball milling exhibit ultrahigh dielectric permittivity 441,543, low loss factor 0.02, good dielectric temperature stability (<15 %) in the temperature range of −55–200 °C, and very high resistance 109Ω, which meets the EIA X9R standard, XPS and impedance spectra indicate that the electron-pinned defect-dipoles effect is the origin of colossal dielectric permittivity and low loss factor. This work shows that Sm-doped SrTiO 3 activated by high-energy ball milling has broad prospects in the applications of thermally-stable miniaturized capacitors. [ABSTRACT FROM AUTHOR]

We studied temperature and frequency dependences of dielectric properties of (1- x )Ca(Fe 1/2 Nb 1/2 )O 3 - x TiO 2 (CFNT) composite ceramics in the ranges of 90–700 K and 10 2 ~10 6 Hz, respectively. Then we detected relaxation in the permittivity formalism. Most interestingly, a large and temperature-independent permittivity of 10 5 could be obtained in the hetero-phase compound with x  = 0.5 by interface engineering. The results were interpreted in terms of Maxwell-Wagner relaxation, which accounts for the fact that the grains and grain boundaries have very different conductivity. [ABSTRACT FROM AUTHOR]

An increasing number of new dielectrics are being reported for the development of next-generation ceramic capacitors for power electronics used in clean energy technologies. Here, high discharge energy density (W dis) ~6.1 J cm−3 with efficiency (η)~72% under a pulsed field (E max) of 410 kV cm−1 is reported along with temperature stability up to 150 °C (E max = 200 kV cm−1) for 0.5 K 0.5 Bi 0.5 TiO 3 -0.42BiFeO 3 -0.08Sm(Mg 2/3 Nb 1/3)O 3 (KBT-BF-SMN) bulk ceramics. The optimised composition is chemically heterogeneous but electrically homogenous, similar to several BiFeO 3 -based dielectrics reported previously and adding to the growing body of evidence that electrical (measured at weak-field) not chemical homogeneity is the best guide to increased E max and enhanced energy density. KBT-BF-SMN ceramics are therefore considered as promising candidates for pulsed power and power electronics applications. • Novel Pb-free K 1/2 Bi 1/2 TiO 3 -BiFeO 3 based high energy density ceramics. • High energy density ~6.1 J cm−3 at 410 kV cm−1 for bulk ceramics. • Desirable electrical homogeneity with highly-resistive electrical components. • Superior permittivity stability (130–600 °C) and pulsed discharge characteristics > 150 °C. • Excellent candidate for next-generation energy density ceramic capacitors. [ABSTRACT FROM AUTHOR]

In this work, Zn-Ni co-modified LiMg 0.9 Zn 0.1- x Ni x PO 4 (x = 0–0.1) microwave dielectric ceramics were fabricated using a solid state synthesis route. Rietveld refinement of the XRD data revealed that all ceramic samples have formed a single phase with olivine structure. SEM images showed that the samples have a dense microstructure, that agrees with the measured relative density of 97.73 %. Based on the complex chemical bond theory, Raman and infrared reflectance spectra, we postulate that ε r is mainly affected by the ionic polarizability, lattice and bond energy, while P-O bond plays a decisive role in Q×f and τ f value. Optimum properties of Q×f ~ 153,500 GHz, ε r ~ 7.13 and τ f ~ −59 ppm/°C were achieved for the composition LiMg 0.9 Zn 0.06 Ni 0.04 PO 4 sintered at 875 ℃ for 2 h. This set of properties makes these ceramics an excellent candidate for LTCC, wave-guide filters and antennas for 5 G/6 G communication applications. [ABSTRACT FROM AUTHOR]

Cordierite-based dielectric ceramics with a lower dielectric constant would have significant application potential as dielectric resonator and filter materials for future ultra-low-latency 5G/6G millimeter-wave and terahertz communication. In this article, the phase structure, microstructure and microwave dielectric properties of Mg 2 Al 4–2 x (Mn 0.5 Zn 0.5) 2 x Si 5 O 18 (0 ≤ x ≤ 0.3) ceramics are studied by crystal structure refinement, scanning electron microscope (SEM), the theory of complex chemical bonds and infrared reflectance spectrum. Meanwhile, complex double-ions coordinated substitution and two-phase complex methods were used to improve its Q×f value and adjust its temperature coefficient. The Q×f values of Mg 2 Al 4–2 x (Mn 0.5 Zn 0.5) 2 x Si 5 O 18 single-phase ceramics are increased from 45,000 GHz@14.7 GHz (x = 0) to 150,500 GHz@14.5 GHz (x = 0.15) by replacing Al3+ with Zn2+-Mn4+. The positive frequency temperature coefficient additive TiO 2 is used to prepare the temperature stable Mg 2 Al 3.7 (Mn 0.5 Zn 0.5) 0.3 Si 5 O 18 - y wt%TiO 2 composite ceramic. The composite ceramic of Mg 2 Al 3.7 (Mn 0.5 Zn 0.5) 0.3 Si 5 O 18 - y wt%TiO 2 (8.7 wt% ≤ y ≤ 10.6 wt%) presents the near-zero frequency temperature coefficient at 1225 °C sintering temperature: ε r = 5.68, Q×f = 58,040 GHz, τ f = −3.1 ppm/°C (y = 8.7 wt%) and ε r = 5.82, Q×f = 47,020 GHz, τ f = +2.4 ppm/°C (y = 10.6 wt%). These findings demonstrate promising application prospects for 5 G and future microwave and millimeter-wave wireless communication technologies. [ABSTRACT FROM AUTHOR]

It is a great challenge to high colossal permittivity (CP, Ɛ r) in polycrystal ceramics together with low dielectric loss (tanδ) and high insulation resistivity (ρ) due to the miniaturization of electrical devices. In this contribution, the defect dipoles [ T i 4 + • e − C e S r • • − e • T i 4 + ] and [ C e S r • − e • T i 4 + ] have been actively induced in the Sr 1-1.5 x Ce x TiO 3 (SCT) systems by doping Ce ions with amphoteric nature to address this issue. The ultra-stable dielectric performance under the external stimulus, with Ɛ r = 12,406 (with low variation of < ±10%) and tanδ <0.08 , can be achieve in the x = 0.01 sample within the temperature range of 10–200 °C and at the frequencies ranging from 20 Hz to 1 MHz, accompanied by high insulation with ρ > 1010 Ω•cm with low degradation rate under harsh test conditions of 2–4.5 kV/cm. This work paves a path by multisite defect engineering to achieve high-performance CP ceramics. [ABSTRACT FROM AUTHOR]

5G and forthcoming 6G communication systems require dielectric ceramics with low relative permittivity (ε r) and near-zero temperature coefficient of resonant frequency (τ f) for the lower part of the microwave (MW) band and at sub-Terahertz. Mg 2 Al 4 Si 5 O 18 (MAS) ceramics are promising candidates due to their low ε r (~ 6) and high-quality factor (Q× f > 40,000 GHz) but have a large τ f. In this study, 5.5 wt% TiO 2 (MAS-T 5.5) was used to adjust τ f of MAS to −2.8 ppm/℃ whilst retaining low ε r (5.24) and good Q× f (33,400 GHz), properties consistent with those obtained by infrared reflectance. A demonstrator microstrip patch antenna with gain 4.92 dBi and 76.3% efficiency was fabricated from MAS-T 5.5. [ABSTRACT FROM AUTHOR]

A novel Li 3 Mg 4 NbO 8 compound was fabricated through the process of solid-state reaction. The crystal structure, sinterability and microwave dielectric properties of the Li 3 Mg 4 NbO 8 ceramics were investigated. XRD refinement and Raman spectra results ascertained that the Li 3 Mg 4 NbO 8 compound crystallized into an orthorhombic Li 3 Mg 2 NbO 6 -like structure with space group Fddd. The ε r value was strongly impacted by the relative density and average ionic polarization. The Q × f value was mainly affected by the relative density and average grain size. The Li 3 Mg 4 NbO 8 ceramics sintered at 1150 ℃ showed outstanding microwave dielectric performance: ε r = 13.8 ± 0.14, Q × f = 103 400 ± 3500 GHz (at 9.6 GHz), τ f = −36.0 ± 1 ppm/℃. Additionally, the bond characteristics were calculated for a better understanding of the structure-property correlation for Li 3 Mg 4 NbO 8 ceramics. [ABSTRACT FROM AUTHOR]

Additive manufacturing via direct ink writing and microwave dielectric characterisation of commercially produced low sintering temperature bismuth molybdenum oxide ceramics, have been both performed for the first time, following a powder-to-product holistic approach. We demonstrated that direct ink writing is an excellent candidate for producing dielectric substrates to be used for wireless telecommunication applications operating at microwave (MW) frequencies, with great repeatability and properties comparable to ceramics fabricated via conventional processing routes. The optimum density (relative density of ρ r ≈ 93%) of the 3D printed test samples was obtained by sintering at 660 °C for 2 h, resulting in a relative permittivity ε r = 35.7, dielectric loss tan δ = 0.0004 and microwave quality factor Q × f = 14,928 GHz. Sintering at higher temperatures promoted a porosity increase due to mismatching grain growth mechanisms and phase decomposition, that collectively hindered the test samples' microwave dielectric performance in terms of achievable relative permittivity (ε r) and dielectric loss (tan δ). [ABSTRACT FROM AUTHOR]

Nb5+ and Ga3+ co-doped Ti 0.9 Zr 0.1 O 2 ceramics were synthesized using the conventional solid-state reaction method. Single rutile-liked phase of octahedron structure were identified for all compositions in (Nb 0.5 Ga 0.5) x (Ti 0.9 Zr 0.1) 1-x O 2 (NGT) with x = 0.01 to 0.10 by X-ray diffraction patterns coupled with Rietveld refinement. Microstructural scanning image, together with energy dispersive x-ray spectroscopy (EDX), revealed good chemical homogeneity in NGT samples. A giant dielectric permittivity of 5 × 104 and a low loss of 0.02 was obtained in NGT with x = 0.01 due to the contribution of electron-pinned and defect-dipole effect. Furthermore, a temperature (-20–120 °C), frequency (0.1–104 Hz) and bias electric field (100–200 V/mm) independent dielectric permittivity and loss was found in this composition, which is critical for potential applications of supercapacitors. [ABSTRACT FROM AUTHOR]

In order to fabricate high performance dielectric capacitors for pulsed power applications, dense and homogenous Bi(Mg 2/3 Nb 1/3)O 3 -modifed BaTiO 3 -based Pb-free relaxor ferroelectric ceramics were obtained through a isostatic pressing technique at room temperature. Obvious relaxor behavior with a high diffusion degree is confirmed by broad and frequency-dependent dielectric peaks in 0.875BaTiO 3 -0.125Bi(Mg 2/3 Nb 1/3)O 3 (BT-0.125BMN). Good energy storage properties including a high recoverable energy density of ∼1.89 J/cm3, an relatively high efficiency of ∼83%, good dielectric/temperature/frequency dependent stability and also fatigue resistance are achieved in this composition at a high electric field of 240 kV/cm, together with a fast discharging speed of <160 nm and high maximum current density of 503.46 A/cm2 and a large power density of 25.12 MW/cm3. These properties indicate that BT-0.125BMN is a promising candidate of capacitors for the pulsed power applications. [ABSTRACT FROM AUTHOR]

It has been a challenge to provide a unified description of the dielectric response vs temperature for ferroelectrics with diffuse phase transition (DPT) and relaxor behaviors, which can be used to fit the dielectric response both below and above the peak temperature (Tm). Most of the available functions used in fitting experimental data only provide a description of the dielectric permittivity near and above Tm. In this work, employing a macroscopic and phenomenological statistical model and using Ba(Ti1−x Zrx)O3 ceramics as an example, we revisit the dielectric permittivity's temperature dependence, analyzing their DPT and relaxor behaviors and providing a complete description over the whole temperature range. We show that good agreements between theoretical and experimental results can be achieved. To better understand how Ba(Ti1−x Zrx)O3 ceramics changes from DPT to relaxor with increasing x, we also discuss the relation between the fitting parameters and Ba(Ti1−x Zrx)O3's composition and structure, which suggests that the parameters from the statistical model reflect the size of the correlated Ti ions (small clusters or polar nanoregions), which largely determine the behavior of Ba(Ti1−x Zrx)O3 ceramics. [ABSTRACT FROM AUTHOR]

• An ultra-low temperature co-fired ceramic was developed using solid state route. • Theoretically calculated and experimentally measured band gaps were consistent. • Lossy nature of the sample was related to impurities, oxygen, and lithium vacancies. • A high specific capacitance of 252.5 F/g was obtained at a scan rate of 5 mV/s. Lithium molybdates are of great interest in ultra-low temperature cofired ceramics (ULTCC) technology due to their low processing temperature. In this study, a ULTCC Li 4 Mo 5 O 17 was prepared via a solid state route. X-ray diffraction and Raman spectroscopy analysis revealed the formation of single phase triclinic structure. The variation in relative permittivity and dielectric loss of the sample with the change in frequency is explained using the polaron model. At the excitation of 514 nm, excitonic and deep-level (impurities, oxygen, and lithium vacancies) emissions were observed which contribute to the lossy nature of Li 4 Mo 5 O 17. The experimentally calculated direct optical band gap energy of ∼ 3.1 eV is consistent with the energy gap (∼ 3.07 eV) predicted through density functional theory. The electrochemical study showed that the sample exhibits a high specific capacitance of ∼ 252.5 F/g at a low scan rate of 5 mV/s. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • 0–3 type composite structure is achieved in the BNT-SBT-ZnO ceramics. • ZnO not only acts as a sintering aid, but also enhances the random fields and polar nanoregions activity by Zn2+ doping. • Obvious element segregation is generated in the BNT-based matrix grains showing different Sr2+/(Bi3+, Na+) ratios. • Optimized energy storage performance is realized with W rec ∼ 5.84 J/cm3, η ∼ 93 %, and E B ∼ 40 kV/mm. In this work, ZnO is introduced into the 0.55Bi 0.5 Na 0.5 TiO 3 -0.45Sr 0.7 Bi 0.2 □ 0.1 TiO 3 (BNT-SBT) to optimize the dielectric energy storage performance. ZnO is not only used as a sintering aid to decrease the sintering temperature and ceramic grain size, but also enhances the random fields and polar nanoregions activity in the ceramics by Zn2+ doping. Intriguingly, the ZnO-modified BNT-SBT ceramics present a 0–3 type composite structure containing the TiZn 2 O 4 and Bi 2 Ti 2 O 7 linear dielectrics. Moreover, obvious element segregation is generated in the BNT-based matrix grains showing different Sr2+/(Bi3+, Na+) ratios and polarization magnitudes. The significant variations in composition distribution, grain and domain configurations cause the overall optimization of energy storage properties, reflected in the enhanced breakdown strength, delayed polarization saturation, and reduced polarization hysteresis. As a result, the optimized W rec ∼ 5.84 J/cm3 and η ∼ 93 % at 40 kV/mm is obtained in the BNT-SBT-0.10ZnO ceramic, superior to that of the BNT-SBT ceramic (W rec ∼ 3.35 J/cm3 and η ∼ 89 % at 28 kV/mm). [ABSTRACT FROM AUTHOR]

Capacitance change for all ceramics at 10 kHz. • In the titled "Origin of ultrahigh thermal stability on dielectric permittivity and dipole glass-like behavior of 0.4Ba0.8Ca0.2TiO3-0.6Bi(Mg0.5Ti0.5)O3 (BCT-BMT) based ceramics" of manuscript, the ultrahigh thermal stability on dielectric permittivity of BCT-BMT based ceramics with a pseudo-cubic crystal structure was prepared. • The dipole glass-like behavior behavior of all ceramics were characterized by a phenomenological statistical model. • The origin of ultrahigh thermal stability on dielectric permittivity is attributed by the weaker interaction between active dipoles and less ferroelectric long-rang order. • The 5 mol% Si doped BCT-BMT ceramics shows that the capacitance variation are lower than ± 5 % (1209 ± 60) between a wide temperature range from 437 K to 796 K with a low dielectric loss (tan δ < 0.025) from 443 K to 714 K, indicating a promising material for use in high-temperature capacitors. The 0.4Ba 0.8 Ca 0.2 TiO 3 -0.6Bi(Mg 0.5 Ti 0.5)O 3 (BCT-BMT) and 5 mol% Si doped 0.4Ba 0.8 Ca 0.2 TiO 3 -0.6Bi(Mg 0.5 Ti 0.5)O 3 (BCST-BMT) ceramics with a pseudo-cubic crystal structure were prepared. Both as-prepared and O 2 annealing ceramics (BCT-BMT-O 2 and BCST-BMT-O 2) exhibit a typical re-entrant dipole-glass-like relaxor behavior and excellent thermal stability of dielectric permittivity above T m. A statistical model was employed to describe the temperature dependence of dielectric permittivity, which reveals the origin of the special dielectric properties. The large dielectric permittivity is attributed to the weakly interacting polar nanoregions (PNRs) associated with complex ionic substitution of both the A-site and B-site. The ultrahigh thermal stability is related to the thermal distribution of active dipoles. The Si doped BCT-BMT ceramic shows that the capacitance variation are lower than ± 5 % (1209 ± 60) in a wide temperature range from 437 K to 796 K with a low dielectric loss (tan δ < 0.025) from 443 K to 714 K, indicating a promising material for use in high-temperature capacitors. [ABSTRACT FROM AUTHOR]