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Tunable dielectric materials, serving as key components in microwave electronic application, require both high dielectric tunability and low dielectric loss. However, the trade-off between dielectric tunability and dielectric loss restricts the improvement of the overall dielectric tunability properties. In the present study, we proposed an effective approach to benefit both high tunability and low dielectric loss, i.e., improving intrinsic dielectric response from the lattice polarization and restricting the extrinsic dielectric response from the domain motions at the same time. Experimentally different acceptor dopants were employed, including the introduction of K at the A-site and Mn, Fe and Co at the B-site. On one hand, the different acceptor dopants could adjust the Curie temperature and consequently resulting in the enhanced intrinsic dielectric response at room temperature. On the other hand, the employment of acceptor dopant could introduce the oxygen vacancies and form the acceptor-oxygen vacancy dipoles which may restrict the reorientation of microdomains, resulting in the decrease of extrinsic dielectric response. Herein, both enhanced tunability and reduced dielectric loss were achieved in acceptor doped BZT ceramics at ambient temperature (27 °C). In particular, Fe doped BZT ceramics achieved both high dielectric tunability of 93.8 % and low dielectric loss of 0.0038. Such performance is competitive with that of previous reported dielectric tunable materials. In addition, the dielectric tunability of Fe doped BZT ceramics maintained over 60 % within the wide temperature range from −20 °C to 60 °C. [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 immense potential of lead-free dielectric capacitors in advanced electronic components and cutting-edge pulsed power systems has driven enormous investigations and evolutions heretofore. One of the significant challenges in lead-free dielectric ceramics for energy-storage applications is to optimize their comprehensive characteristics synergistically. Herein, guided by phase-field simulations along with rational composition-structure design, we conceive and fabricate lead-free Bi0.5Na0.5TiO3-Bi0.5K0.5TiO3-Sr(Sc0.5Nb0.5)O3 ternary solid-solution ceramics to establish an equitable system considering energy-storage performance, working temperature performance, and structural evolution. A giant Wrec of 9.22 J cm−3 and an ultra-high ƞ ~ 96.3% are realized in the BNKT-20SSN ceramic by the adopted repeated rolling processing method. The state-of-the-art temperature (Wrec ≈ 8.46 ± 0.35 J cm−3, ƞ ≈ 96.4 ± 1.4%, 25–160 °C) and frequency stability performances at 500 kV cm−1 are simultaneously achieved. This work demonstrates remarkable advances in the overall energy storage performance of lead-free bulk ceramics and inspires further attempts to achieve high-temperature energy storage properties. One of the key challenges in dielectric ceramics for energy storage lies in the comprehensive optimization of their properties. Here, the authors establish an equitable system considering performance and structure evolution in a lead-free ceramic capacitor, achieving a broad-high temperature performance. [ABSTRACT FROM AUTHOR]

Dielectric ceramics are fundamental for electronic systems, including energy storages, microwave applications, ultrasonics, and sensors. Relaxor ferroelectrics show superb performance among dielectrics due to their high efficiency and energy density by the nature of nanodomains. Here, a novel non‐perovskite relaxor ferroelectric, Bi6Ti5WO22, with ultralow loss, ≈10−3, highly tunable permittivity, ≈2200 at room temperature with 40% tunability and the superparaelectric region at room temperature is presented. The actual crystal structure and the nanodomains of Bi6Ti5WO22 are demonstrat Various‐temperature neutron powder diffraction and in situ high‐resolution transmission‐electron‐microscopy illustrate the twinning effect, subtle structure change and micro‐strain in the material influenced by temperature, manifesting the actual crystal structure of Bi6Ti5WO22. Compared with dielectric loss of BaTiO3‐based dielectric tunable materials, the loss of Bi6Ti5WO22 is more than an order of magnitude lower, which makes it exhibit a figure of merit (≈240), much higher than that of conventional dielectric tunable materials (< 100), endorse the material great potential for direct applications. The present research offers a strategy for discovering novel relaxor ferroelectrics and a highly desirable material for fabricating energy storage capacitors, microwave dielectrics, and ultrasonics. [ABSTRACT FROM AUTHOR]

• Multi-state memory in BaTiO 3 ceramics was successfully realized by acceptor-doping. • Four independently addressed memory states were obtained in the double hysteresis loop. • The effect of dopants on memory effect was systematically studied by substitute site. • Pronounced memory effect in K-doped samples implies precise information recognition. • Better fatigue resistance in Fe-doped samples benefits the enhancement of service life. In the present study, acceptor-doped Ba 0.99 K 0.01 TiO 3 and BaTi 0.99 Fe 0.01 O 3 ceramic samples were prepared by the conventional solid-state reaction method. Antiferroelectric-like double hysteresis loops with four distinct memory states were realized in both A-site K-doped and B-site Fe-doped BaTiO 3 samples, providing a possibility to achieve multi-state memories. The practice feasibility of the memory effect was verified by write/read operations. The experimental results showed that the A-site K-doped sample demonstrated a pronounced memory effect, while the B-site Fe-doped sample showcased an enhanced fatigue resistance. Moreover, the differences in the shapes of hysteresis loops and related parameters of memory effect between K-doped and Fe-doped samples were systematically investigated from the view of acceptor-substitute site. All the results indicated that acceptor-doped BaTiO 3 ceramics were greatly promising for multi-state memory. [Display omitted] [ABSTRACT FROM AUTHOR]

In the present study, an industrially viable ceramics fabrication way based on solid-state reaction method–semi-solution method was used to improve the dielectric and ferroelectric properties of acceptor-donor co-doped BaTiO 3 ceramics. Unlike the conventional solid-state reaction method, additives in the semi-solution method were introduced in the form of the aqueous solution rather than oxide powders. Experiment results show that higher peak dielectric constant ε m a x (140–150%), larger maximum polarization P m a x (24 μ C cm−2), and less apparent aging phenomena were achieved by the semi-solution method. A comprehensive microscopic analysis was carried out to explore the origin of property enhancement. Results show that enhanced properties could be ascribed to the higher level of compositional homogeneity and lower content of oxygen vacancies. This study provides a new method to control aging phenomena and achieve property enhancement in acceptor-donor co-doped ceramics. Moreover, this simple and cost-effective method may also find its application in other extensive-doped ceramics. [ABSTRACT FROM AUTHOR]

The piezoelectric performance, both weak-signal piezoelectric coefficient d 33 or large-field electrostrain, were systemically measured from room temperature until their Curie temperature. Large piezoelectric coefficient d 33 of 920 pC/N was found on the boundary between the tetragonal (T) and the orthorhombic (O) phase (around 50 °C) rather than the quadruple point with lowest free energy barrier. Further simulation work based on the Landau free energy function also supported the experimental results, owing to the joint effect of the anisotropy energy and the order parameter polarization. Besides, the electrostrain of 0.15% with small hysteresis was also found on the O-T boundary. Systemically study pointed out that polarization rotation would have a significant contribution to the overall piezoelectric response. [ABSTRACT FROM AUTHOR]

In the present study, BaTi 0.8- x Zr 0.2 Mn x O 3 (x = 0, 0.25 %, 0.5 %, 0.75 %) ceramics were prepared via a solid-state reaction process. Results showed that both enhanced tunability of 93.4 % (at 20 kV/cm and 27 °C) and reduced dielectric loss tangent of 0.005 at 10 kHz were achieved in BaTi 0.8- x Zr 0.2 Mn x O 3 ceramics at x = 0.5 %. Such dielectric tunability was higher than that of common materials whose tunability hardly exceeded 85 %. Moreover, the mechanism of enhanced dielectric tunability was discussed. The contribution of the intrinsic polarization to the dielectric tunability increased with the increase of Mn content, leading to a higher tunability. Meanwhile, the "domain pinning" effect of M n Ti ″ − V O ● ● × defect dipoles restricted the reorientation of microdomains, thus decreasing extrinsic contribution and dielectric loss tangent. Furthermore, the tunability for the BaTi 0.8- x Zr 0.2 Mn x O 3 (x = 0 %, 0.25 %, 0.5 %, 0.75 %) samples was measured in the temperature range of − 30 to 85 °C, showing a favorable dielectric tunable performance with good temperature stability. • High tunability of 93.4% and relatively low dielectric loss tangent of 0.005 at 10 kHz were obtained. • Superior thermal stability was obtained in Mn-doped BaTi 0.8 Zr 0.2 O 3 ceramics. • Effect of Mn doping on dielectric tunability and dielectric loss tangent was revealed. [ABSTRACT FROM AUTHOR]

In the present study, BaTi (1- x) M x O 3 (x = 0.005, 0.01, 0.015; M is Mn, Fe, and Co) ceramics were prepared by the conventional solid-state reaction method. Four distinct and independently addressed memory states were experimentally obtained based on the double hysteresis loop, which was achieved by acceptor doping in BaTiO 3 ceramics. Moreover, this study indicated that for acceptor-doped BaTiO 3 ceramics, larger electronegativity and smaller ionic radius of acceptor ions benefitted the more significant memory effect and better fatigue resistance. All these results could provide a promising solution for multi-state memory applications. • Acquired four independently addressed memory states from the double hysteresis loop in the acceptor-doped BaTiO 3 ceramics. • Doping acceptor dopants with large electronegativity and small ionic radius could induce a more remarkable memory effect. • Enhanced fatigue resistance of the memory effect was achieved, which made the present ceramics promising for applications. [ABSTRACT FROM AUTHOR]

In the present study, pure and donor–acceptor co-doped Ba 0.675 Sr 0.325 TiO 3 (BST) ceramics were prepared by the conventional solid-state reaction method. La was fixed as the donor dopant at A-site while Mn, Cr, and Fe were selected as the acceptor dopants at B-site. The effect of acceptor dopants on the microstructure and electrical properties of BST ceramics was investigated systematically from the view of different ionic radius and electronegativity. Enhanced dielectric tunability and reduced dielectric loss could be realized by co-doping, resulting in a significant improvement in the figure of merit (FOM). The optimum tunable properties were obtained in Mn–La co-doped ceramics with the dielectric tunability of 85.1%, the dielectric loss of 0.0018, and the FOM of 472. Such results could be attributed to the smaller ionic radius and weaker electronegativity of Mn. Compared to pure BST ceramics with the FOM of 40, co-doped BST ceramics exhibited great potential for tunable device applications. The breakdown strength (BDS) of BST ceramics was also studied in this work. Improved breakdown strength by co-doping took better stability for its applications under applied electric field. • High dielectric tunability and reduced dielectric loss were achieved by co-doping. • Significant improvement was realized in the figure of merit from 40 to 472. • The breakdown strength was enhanced by 74%. • Effect of dopants was studied by varied ionic radius and electronegativity. • Co-doped ceramics exhibited great potential for tunable device applications. [ABSTRACT FROM AUTHOR]

The intrinsic mission in the field of electrical insulation is to make the insulator or the power equipment withstand voltage as high as possible. On one hand, extensive research has focused on improving insulation materials or optimizing the design to endure higher voltage, whereas on the other hand, efforts have addressed the suppression of voltage surges because this indirectly improves the capability of the equipment to withstand higher voltages. ZnO varistors, exhibiting excellent nonlinear I-V characteristics, are specialized in discharging transient surges and limiting the voltage to a magnitude that is not harmful to power equipment. Because of their good price-to-performance ratio, ZnO varistors are the most common overvoltage protection component in AC power protectors. The discovery of the nonlinear I-V characteristics of ZnO ceramics in the 1960s [1] trigged interest in scientific research and industry [2]?[7]. The mysteries about the interfacial states at the grain boundaries and the point defect structures have attracted much attention from theoretical and experimental aspects. As a result, ZnO varistors developed rapidly to meet new challenges from the power system and electronic sectors. ZnO varistors developed rapidly during the past 30 years, not only in China but also in the world, and benefited from the contributions of the universities on the fundamentals and key processing techniques. The objective of this article is to give an overview of the research carried out over the last 30 years that has contributed to the development of ZnO varistors in a broad sense. We emphasize, in our view, the remarkable progress in the fundamental research, which has revealed the physical origin of the obtained properties, the key processing techniques, which have provided important guidance on how to obtain ZnO ceramics with the required performance, and the advanced products now available from industry. [ABSTRACT FROM PUBLISHER]

In the present study, the doping effect of SiO2 on the dielectric, ferroelectric and piezoelectric properties of the (Ba0.7Ca0.3)(Zr0.2Ti0.8)O3 ?abbreviated as BZT-50BCT hereafter? ceramics sintered at different temperatures were systematically studied. With the SiO2 dopant, the distribution of the grain size became more homogeneous. Besides, the average grain sizes firstly increased with increasing the SiO2 concentrations and then decreased. As the macroscopic properties, the dielectric constant decreased with the addition of SiO2. The remnant polarization Pr firstly increased and then decreased with increasing the SiO2 concentration. While the coercive field monotonically decreased with the SiO2 dopant. And the piezoelectric constant d33 firstly enhanced by the SiO2 and then reduced as further increasing the SiO2 concentrations. The maximum d33 of 500 pC/N has been obtained in the 0.5 mol% SiO2 doped BZT-50BCT ceramics sintered at 1500° from the industry available raw materials. [ABSTRACT FROM AUTHOR]

• Achieve the high dielectric tunability and the reduced dielectric loss by La/Fe co-doping in Ba 0.65 Sr 0.35 TiO 3 ceramics. • Improve the figure of merit to 197 which is nearly 5 time compared to the pure Ba 0.65 Sr 0.35 TiO 3 ceramics. • Enhance the breakdown strength by 86% due to the reduced grain size and dense microstructure. In the present study, (Ba 0.65 Sr 0.35) 1−x La x Ti 1−x Fe x O 3 (x = 0, 0.0025, 0.005, 0.01) ceramics were designed and prepared by the conventional solid-state reaction method. The microstructures and electrical properties of La/Fe co-doped Ba 0.65 Sr 0.35 TiO 3 ceramics were investigated. Enhanced dielectric tunability and reduced dielectric loss were achieved in this system. The acceptor dopant Fe3+ was used to lower dielectric loss while the donor dopant La3+ was added to improve dielectric tunability. The optimum tunable properties took place at x = 0.0025 with the dielectric tunability = 78.8% and the dielectric loss = 0.0040. The figure of merit (FOM) was improved to 197, about five times that of pure BST. The breakdown strength (BDS) enhanced from 59.9 kV/cm to 111.4 kV/cm by La3+ and Fe3+ dopant, which promoted the stability of BST ceramics under high applied electric field. In conclusion, excellent tunable properties and improved breakdown strength made it possible for the La/Fe co-doped BST ceramics to be promising for tunable microwave applications. [ABSTRACT FROM AUTHOR]

In the present study, we designed a new system, Ba(Ti 0.99-1.25 x Mn 0.01 Nb x)O 3 (x = 0.5%, 1.0%, 1.25%, 1.5%), to improve the energy storage properties of BaTiO 3 –based ceramics. Here the acceptor dopant Mn was introduced to enhance the maximum polarization P max while reducing the remnant polarization P r by inducing aging phenomena. The donor dopant Nb was added to make the hysteresis loop slimmer and slender through 'softening' effect. And the ratio of acceptor and donor was adjusted to modify the energy storage properties by modulating the shape of hysteresis loop. Results showed that an enhancement of 76% over pure BaTiO 3 in recoverable energy storage density (W rec) has been achieved in hybrid-doped samples, accompanied by a high energy conversion efficiency (η) up to 86%. Hereinto, donor-dominant samples doped with 1% Mn and 1.25% Nb exhibited the highest W rec and η with excellent thermal stability. This study proved the feasibility of enhancing the energy storage properties by hybrid doping and may provide a new viewpoint for later studies. Image 1 • Enhancement of energy storage properties of BaTiO 3 -based ceramics by simple hybrid-doping. • Defect-induced antiferroelectric-like double hysteresis loop. • Modification of the hysteresis loop by adjusting donor acceptor ratio. • Synergy effect of aging phenomena and softening effect. [ABSTRACT FROM AUTHOR]

In the present study, both enhanced voltage gradient of 803 V/mm and superior energy absorption capability of 400 J/cm3 were achieved in ZnO varistors prepared by nano-sized raw powders. Further analysis indicated that such improvement could be ascribed to the refined micromorphology. As shown by SEM pictures, the average grain size was dramatically decreased by the nano-sized powders, which contributed to the enhanced voltage gradient. Meanwhile, the homogeneous grain size distribution resulted in the improved energy absorption capability. The improved varistors in the present study showed high potential for ultra-high voltage applications. In addition, we proposed an effective approach to quantitatively evaluate the grain size distribution, which is the key parameter for the electrical properties of the varistors. It provided a guideline for further modifications on wide range of electronic ceramics. • ZnO varistor ceramics with fine grains and uniform grain size distribution were prepared by using nano-sized powders. • High voltage gradient of 803 V/mm and energy absorption capability of 400 J/cm3 were obtained in ZnO varistor ceramics. • An effective approach was proposed to quantitatively evaluate the uniformity of grain size distribution. [ABSTRACT FROM AUTHOR]

Piezoelectric ceramics is a functional material that can convert mechanical energy into electrical energy and vice versa. It can find wide applications ranging from our daily life to high-end techniques and dominates a billion-dollar market. For half a century, the working horse of the field has been the polycrystalline PbZr1−xTixO3 (PZT), which is now globally resisted for containing the toxic element lead. In 2009, our group discovered a non-Pb piezoelectric material, (BaCa)(ZrTi)O3 ceramics (BZT-BCT), which exhibits an ultrahigh piezoelectric coefficient d33 of 560–620 pC/N. This result brought extensive interest in the research field and important consequences for the piezoelectric industry that has relied on PZT. In the present paper, we review the recent progress, both experimental and theoretical, in the BZT-BCT ceramics. [ABSTRACT FROM AUTHOR]

• Simultaneously enhanced stability and nonlinearity were obtained in ZnO varistors. • The intrinsic donor defects of Si-doped varistors were quantified for the first time. • Relations between donor defects and Si-stabilized δ -Bi 2 O 3 phase were clarified. In the present study, simultaneously enhanced electrical stability (low degradation rate of 8.0 × 10−3 mA∙ h1/2) and high nonlinear coefficient of 56 were obtained in ZnO varistors by doping SiO 2. To clarify the mechanism of enhanced properties, comprehensive microscopic analyses were studied. Particularly, the intrinsic point defects were quantitatively characterized for the first time. Results showed that the densities of zinc interstitials (Zn i) and oxygen vacancies (V o) were dramatically decreased, resulting in enhanced stability. Besides, reduced Zn i and V o decreased the total donor density, contributing to the improved barrier height and thus leading to enhanced nonlinearity. Combined with XRD and SEM results, it is deduced that such reduced Zn i and V o are attributed to the Si-stabilized high oxygen conducting δ -Bi 2 O 3 phase. Furthermore, this elucidated mechanism, which has been long neglected in Si-doped varistors, may provide valuable insights into further developing high-performance ZnO varistors. [ABSTRACT FROM AUTHOR]

In the present study, the BaTiO 3 ceramic from fine powder with the average particle size of 400 nm and with high tetragonality of 1.0103 was fabricated via solid-state route by employing two step pre-treatments. One is the wet ball milling of the commercially available BaCO 3 powder which solved the agglomeration problem and increased the contact points during calcination. The other one is the dry milling of the calcined BaTiO 3 powder which separated the powder into single particles and enhanced the stacking density during sintering. The obtained BaTiO 3 ceramics showed enhanced dielectric constant of 12,000 at Curie temperature of 125 °C, ferroelectric remnant polarization of 5.33 μC/cm 2 and coercive field of 163 V/mm. Besides, the improved BaTiO 3 ceramics showed piezoelectric constant d 33 of 200 pC/N, which was enhanced by 53.8% from the 130 pC/N of the normal BaTiO 3 ceramic. [ABSTRACT FROM AUTHOR]

The excellent dielectric constant (ε r) and breakdown strength (E b) of dielectric nanocomposites are the necessary conditions for their excellent energy storage properties (ESPs) in microelectronics and power systems. In recent years, inorganic nanofillers and multilayer structure design have provided an efficient way to improve the ESPs of dielectric composites. Herein, we selected 0.8Bi 0.5 (Na 0.82 K 0.18) 0.5 TiO 3 -0.2Sr(Sc 0.5 Nb 0.5)O 3 cecamic nanoparticles (BNKT-SSN NPs) with high ε r and low loss as nanofillers, and prepare novel trilayer structured BNKT-SSN/P(VDF-HFP) nanocomposites to improve the ε r and E b. The investigated phenomena demonstrate that due to the contribution of BNKT-SSN NPs incorporation and interfacial polarization between neighboring layers, the ε r and E b of the trilayer structured BNKT-SSN/P(VDF-HFP) nanocomposites are enhanced while the dielectric loss (tan δ) and leakage current density are suppressed. It is worth noting that the E b is measured up to 650 MV m−1 when the intermediate layer fillers BNKT-SSN NPs of the trilayer structured nanocomposite is 0.75 vol%, and the discharged energy density (U d) and energy efficiency (η) are 25.79 J cm−3 and 70.07 %, respectively. In this work, it's demonstrates that the incorporation of inorganic ceramic fillers and the trilayer structured design provide a feasible approach of improving the ESPs of dielectric nanocomposites. [Display omitted] • The ceramic and sandwich structure work together to improve the ε r and E b. • The electric field distribution is simulated by finite element method. • The insulation and mechanical properties of nanocomposites are enhanced. • The optimal U d and η of the composite at 650 MV m−1, are 25.79 J cm−3 and 70.07 %. [ABSTRACT FROM AUTHOR]

Intrinsic point defect structure plays a crucial role in functional ceramics with a grain-grain boundary microstructure. In the present study, a novel method of reversely manipulating intrinsic point defects (oxygen vacancy, V o and zinc interstitial, Zn i ) in ZnO-based varistor ceramics is proposed, which makes use of Zr-stabilized high ionic conducting β III -Bi 2 O 3 intergranular phase. It is found that Zr-doping not only modifies the grain growth by the formation of secondary Zr-rich phase, but also influences the intrinsic point defect structure via the stabilized β III -Bi 2 O 3 phase, resulting in reduced V o density but increased Zn i density. The reverse manipulation is unambiguously demonstrated by broadband dielectric spectroscopy and further confirmed by the accelerated ageing experiment. The proposed intrinsic point defect dynamics unveil an important but usually neglected function of the dopant that has little solid solubility in ZnO grains, which opens up a promising way to tailor the material property. [ABSTRACT FROM AUTHOR]