High-performance piezoelectric ceramics are indispensable in modern electromechanical systems, and multi-component materials like quaternary Pb(In_1/2Nb_1/2)O₃-Pb(Zn_1/3Nb_2/3)O₃-PbZrO₃-PbTiO₃ (PIN-PZN-PZ-PT) have attracted significant attention due to their unique properties at the morphotropic phase boundary (MPB). However, to achieve enhanced piezoelectric and thermal performance by design and optimization for MPB compositions through precisely adjusting the PbTiO₃ (PT) content is facing major challenges. Here, the ceramics were synthesized using a conventional solid-state reaction method, and the MPB compositions were initially predicted by employing a linear combination rule that accounts for the contributions of each component. The predicted phases were then confirmed by X-ray diffraction (XRD) analysis, followed by comprehensive electrical tests to measure the piezoelectric constant (d₃₃) and Curie temperature (T_C). Experimental results reveal that the MPB position is strongly influenced by PT content. As the PT fraction increases, the rhombohedral phase gradually decreases while the tetragonal phase becomes predominant, thus shifting the phase equilibrium. Specifically, the optimal composition (x) ranges are 0.245-0.265 for (1-x)(0.3PIN-0.6PZN-0.1PZ)-xPT, 0.290-0.330 for (1-x)(0.3PIN-0.5PZN-0.2PZ)-xPT, and 0.305-0.345 for (1-x)(0.3PIN-0.4PZN-0.3PZ)-xPT. Notably, the 0.735(0.3PIN-0.6PZN-0.1PZ)-0.265PT sample exhibits superior performance with a d₃₃ of 425 pC/N and a T_C of 253 ℃. These findings demonstrate that precise modulation of the PT content is crucial for controlling the phase balance at the MPB and thereby optimizing the piezoelectric properties. In conclusion, this study successfully identifies the optimal MPB compositions for PIN-PZN-PZ-PT ceramics, highlighting their promising potential for advanced piezoelectric applications and laying a solid foundation for future process improvements and long-term stability research.

Lead magnesium niobate-lead titanate (PMN-PT) piezoelectric single crystals are widely utilized due to their outstanding performance, with varying compositions significantly impacting their properties. While application of PMN-PT in high-power settings is rapidly evolving, material parameters are typically tested under low signal conditions (1 V), and effects of different PT (PbTiO₃) contents on the performance of PMN-PT single crystals under high-power conditions remain unclear. This study developed a comprehensive high-power testing platform using the constant voltage method to evaluate performance of PMN-PT single crystals with different PT contents under high-power voltage stimulation. Using crystals sized at 10 mm×3 mm×0.5 mm as an example, this research explored changes in material parameters. The results exhibit that while trend of the parameter changes under high-power excitation was consistent across different PT contents, degree of the change varied significantly. For instance, a PMN-PT single crystal with 26% (in mol) PT content exhibited a 25% increase in the piezoelectric coefficient $d_{31}$, a 13% increase in the elastic compliance coefficient $s_{11}^{E}$, a 17% increase in the electromechanical coupling coefficient $k_{31}$, and a 73% decrease in the mechanical quality factor $Q_{\mathrm{m}}$ when the power reached 7.90 W. As the PT content increased, the PMN-PT materials became more susceptible to temperature influences, significantly reducing the power tolerance and more readily reaching the depolarization temperatures. This led to loss of piezoelectric performance. Based on these findings, a clearer understanding of impact of PT content on performance of PMN-PT single crystals under high-power applications has been established, providing reliable data to support design of sensors or transducers using PMN-PT as the sensitive element.

In the post-Moore era, temporary bonding and ultra-thin wafer thinning of large-size functional wafers have emerged as essential technologies underpinning innovation within the semiconductor industry. However, challenges such as wafer warpage and breakage commonly encountered during wafer thinning severely limit device performance and yield. To address these issues, WAN’s group at Yongjiang Laboratory developed a cost-effective, room-temperature ultra-flat temporary bonding technique. This innovative process has significantly reduced the risk of wafer warpage while achieving high flatness and stability in wafer bonding. By integrating this process with domestically developed thinning equipment, the group successfully thinned 8-inch silicon wafers down to 8 µm, 12-inch silicon power chips to 15 µm with a total thickness variation (TTV) ≤2 µm, and 8-inch lithium niobate wafers to 8-10 µm, thereby satisfying diverse piezoelectric micro-electro-mechanical system (MEMS) application demands. Currently, this technology is widely applied in heterogeneous integration of various wafer materials, including silicon, lithium niobate/lithium tantalate, gallium oxide, and indium phosphide, providing crucial support for the localization and development of power chips and high-performance MEMS devices.

To further expand the application of advanced ceramic materials in helicopters, this paper reviews their application in helicopter structures both domestically and internationally. It emphasizes the technical maturity and development trends of various ceramic materials in helicopter specific structural applications, such as energy impact protection parts, energy conversion components, and corrosion protection areas. By comparing the gaps between domestic and international use of advanced ceramic materials in helicopter specific structures, the paper provides suggestions for the future development. Recommendations include the use of reaction-sintered contoured integrated opaque armor ceramics and polycrystalline transparent armor ceramics for the high-speed dynamic impact energy protection parts, cermet composite coatings compatible with epoxy resin composite substrates for the low-energy impact protection parts, and hybrid ceramic matrix composite/polymer matrix composite (HCMC-PMC) materials for the thermal shock protection parts. Additionally, multifunctional composite materials, such as high-performance miniature piezoelectric ceramic thin film functional devices and flexible hybrid electronic structures based on micro-piezoelectric ceramic materials, should be developed for the mechanical and electrical energy conversion components. Microwave-absorbing ceramic composites derived from polymer-derived ceramics that are compatible with epoxy resin composite substrates are recommended for the electromagnetic and thermal energy conversion components. Furthermore, high-performance abrasion-resistant and corrosion-resistant Sol-Gel coatings are suggested for the corrosion protection areas. It is also essential to establish a high-speed dynamic energy impact protection mechanism for helicopters, optimize the ballistic performance of protective materials, and develop advanced ceramic materials digital testing and verification technologies, represented by multi-functional composite materials for helicopter specific structures. These efforts will greatly shorten the application cycle of advanced ceramic materials and reduce the verification cost.

With the rapid development of new aerospace vehicles, there are increasing demands for higher structural reliability and wideband microwave stealth requirements for the components operating under high-temperature condition. SiBCN based metastable ceramics exhibit good resistance to high temperature, thermal shock, ablation, long-term oxidation, and creep, showcasing great potential in the field of high-temperature structural microwave absorption. However, their ability to absorb electromagnetic waves is limited by low dielectric loss. In this study, the SiBCN-rGO ceramic fibers with good mechanical and microwave-absorbing properties were prepared using the wet spinning technology. Results showed that the as-prepared SiBCN-rGO ceramic fibers possessed porous structure, with porosity increasing with the increase of reduced graphene oxide (rGO) content. Additionally, both high rGO content and high fiber specific surface area promoted the crystallization of SiC within the amorphous matrix. The introduction of rGO significantly enhanced the tensile properties of the resulting ceramic fibers. As the mass fraction of rGO increased from 0 to 4%, the fibers’ elongation at break increased from 8.05% to 18.05%, and the tensile strength increased from 1.62 cN/dtex (0.324 GPa) to 2.32 cN/dtex (0.464 GPa). The increase of rGO content also reduced the electrical resistivity of the ceramic fibers. Moreover, as the rGO mass fraction increased from 0 to 4%, both the real and imaginary parts of the fibers’ dielectric constant decreased, while the loss tangent gradually increased. The SiBCN-rGO ceramic fibers with those containing 6% (mass fraction) rGO exhibited excellent wave-absorption performance, showing the minimum reflection coefficient of -50.90 dB at 9.20 GHz and an effective absorption bandwidth of 2.3 GHz, indicating promising applications in wave-absorbing ceramic matrix composites.

Potassium-sodium niobate (K_0.5Na_0.5NbO₃) based piezoelectric ceramics are considered the most potential lead-free piezoelectric ceramics due to their excellent piezoelectric coefficient (d₃₃) and high Curie temperature (T_C). However, the temperature stability of its d₃₃ is poor in comparison with the Pb-based piezoelectric ceramics. To solve this problem, (K_0.5Na_0.5)_0.96Li_0.04(Nb_0.95Sb_0.05)O₃-(Bi_0.5Na_0.5)ZrO₃ (KNLNS-BNZ) piezoelectric ceramic with a single tetragonal phase (T phase) was designed and prepared by the conventional solid-state sintering method and texture engineering. It was found that KNLNS-BNZ-based textured ceramic with T phase at room temperature not only possessed a good piezoelectric coefficient (d₃₃=256 pC∙N^-1) and a longitudinal electromechanical coupling coefficient (k₃₃=34%), but also exhibited excellent temperature stability of d₃₃ and k₃₃ in comparison to the non-textured ceramics. The change rates of d₃₃ and k₃₃ for KNLNS-BNZ-based textured ceramics were 12% and 4% with the measured temperature of 25-250 ℃, respectively. In addition, the 1-3 type transducer composed of KNLNS-BNZ-based textured ceramics and epoxy resin was also prepared and investigated. This 1-3 type transducer not only exhibited a large bandwidth (BW=61.2%) and excellent signal strength (f_c=1 MHz), but also showed excellent temperature stability. As the measured temperature increased to 100 ℃, its bandwidth BW and center frequency f_c were 58.7% and 0.94 MHz, whose rates of change were 4% and 6% in comparison to the results measured at room temperature, respectively. All these results show that KNLNS-BNZ lead-free piezoelectric ceramics have good piezoelectric properties and excellent temperature stability, and the 1-3 type transducer prepared by KNLNS-BNZ can provide reference for the practical application of new lead-free piezoelectric ceramics.

The lithium-based silicate microwave dielectric ceramics with ultra-low permittivity show great potential as substrate materials in the fifth-generation wireless communication technology. However, the residual stress caused by higher sintering temperatures leads to increased dielectric loss, thereby deteriorating the microwave dielectric performance. In this work, B³⁺ was introduced into LiAlSi₂O₆ ceramics to reduce Al³⁺ content, aiming to improve their sintering temperature and microwave dielectric performance. LiB_xAl_1-xSi₂O₆ (0≤x≤0.20) microwave dielectric ceramics were prepared using a combination of solid-state reaction and cold isostatic pressing techniques. Effects of B³⁺ doping on the sintering characteristics, phase structure, microstructure, and microwave dielectric properties of the materials were characterized. The results show that with a gradual increase in the doping concentration, sintering temperature of the ceramics decreases significantly from 1400 to 1000 ℃. Meanwhile, the relative permittivity (ε_r) decreases from 3.95 to 3.69, the quality factor (Q×f) increases significantly from 24300 to 30560 GHz, and the temperature coefficient of resonant frequency (τ_f) increases from -45.9×10^-6 to -20.9×10^-6 ℃^-1. Specifically, the change in ε_r is mainly influenced by intrinsic polarization, lattice vibrations, and covalent bond strength of the material; the improvement in Q×f is closely related to the increase in packing fraction (PF) and the decrease in damping coefficient; the increase in τ_f is strongly correlated with the bond valence of oxygen (V_O). Furthermore, the composition with x = 0.20 exhibits the best microwave dielectric performance with ε_r = 3.69, Q×f = 30560 GHz, and τ_f = -20.9×10^-6 ℃^-1. Findings of this study on LiB_xAl_1-xSi₂O₆ provide important theoretical guidance and practical insights for development and application of high-performance microwave dielectric ceramics in the future.

The accepted doping ion in Ti⁴⁺-site of PbZr_yTi_1-yO₃ (PZT)-based piezoelectric ceramics is a well-known method to increase mechanical quality factor (Q_m), since the acceptor coupled by oxygen vacancy becomes defect dipole, which prevents the domain rotation. In this field, a serious problem is that generally, Q_m decreases as the temperature (T) increases, since the oxygen vacancies are decoupled from the defect dipoles. In this work, Q_m of Pb_0.95Sr_0.05(Zr_0.53Ti_0.47)O₃ (PSZT) ceramics doped by 0.40% Fe₂O₃ (in mole) abnormally increases as T increases, of which the Q_m and piezoelectric coefficient (d₃₃) at room temperature and Curie temperature (T_C) are 507, 292 pC/N, and 345 ℃, respectively. The maximum Q_m of 824 was achieved in the range of 120-160 ℃, which is 62.52% higher than that at room temperature, while the dynamic piezoelectric constant (d₃₁) was just slightly decreased by 3.85%. X-ray diffraction (XRD) and piezoresponse force microscopy results show that the interplanar spacing and the fine domains form as temperature increases, and the thermally stimulated depolarization current shows that the defect dipoles are stable even the temperature up to 240 ℃. It can be deduced that the aggregation of oxygen vacancies near the fine domains and defect dipole can be stable up to 240 ℃, which pins domain rotation, resulting in the enhanced Q_m with the increasing temperature. These results give a potential path to design high Q_m at high temperature.

With upgrading of communication technology and driving of 5G communication applications, the explosive number of filters required by various smart devices promoted prosperity of the filter market. However, the demanded performance also becomes increasingly stringent, including broad bandwidth, high frequency, high power capacity, miniaturization, integration, and low cost, in both academia and industry. To meet these strict requirements, the thin film bulk acoustic resonator (FBAR) filters have emerged as one of the most promising types of filters with commercial success. But currently they are still facing difficulties such as insufficient performance, complex fabrication process, relatively higher cost, and technological constraints. This paper reviews the relevant issues and key technologies in FBAR filters in three aspects: theoretical research on devices and structural optimization, preparation and optimization of high-performance piezoelectric materials, and development of novel processes and technological integration. The purpose of this paper is to delineate the trajectory of technological advancements and iterations in FBAR filters for scholars in the research field, with the expectation of providing several considerations for future research directions and pathways.

Ceramic dielectric materials with high dielectric strength and mechanisms of their internal factors affecting dielectric strength are significantly valuable for industrial application, especially for selection of suitable dielectric materials for high-power microwave transmission devices and reliable power transmission. Pure magnesium oxide (MgO), a kind of ceramic dielectric material, possesses great application potential in high-power microwave transmission devices due to its high theoretical dielectric strength, low dielectric constant, and low dielectric loss properties, but its application is limited by high sintering temperature during preparation. This work presented the preparation of a new type of multiphase ceramics based on MgO, which was MgO-1%ZrO₂-1%CaCO₃-x%MnCO₃ (MZCM_x, x = 0, 0.25, 0.50, 1.00, 1.50, in molar), and their phase structures, morphological features, and dielectric properties were investigated. It was found that inclusion of ZrO₂ and CaCO₃ effectively inhibited excessive growth of MgO grains by formation of second phase, while addition of MnCO₃ promoted the grain boundary diffusion process during the sintering process and reduced activation energy for the grain growth, resulting in a lower ceramic sintering temperature. Excellent performance, including high dielectric strength (E_b = 92.3 kV/mm) and quality factor (Q × f = 216642 GHz), simultaneously accompanying low dielectric loss (< 0.03%), low temperature coefficient of dielectric constant (20.3×10^-6 ℃^-1, 85 ℃) and resonance frequency (-12.54×10^-6 ℃^-1), was achieved in MZCM_1.00 ceramics under a relatively low sintering temperature of 1350 ℃. This work offers an effective solution for selecting dielectric materials for high-power microwave transmission devices.

CaBi₂Nb₂O₉ (CBN) thin films with a bismuth layered structure are important precursors for ferroelectric memories, due to their high fatigue resistance, and good ferroelectric properties. The epitaxial growth of CBN along the a-axis is desirable for the integration and application. However, the structural anisotropic makes it challenging to regulate the polarization with respect to the crystallography. In this paper, a new strategy is proposed for the growth of a-axis oriented CBN thin films on MgO(100) single crystal substrate. This strategy is realized by changing the deposition temperature using the pulsed laser deposition technique. The CBN thin films are grown along (115)-, (200)-, and (00l)-crystallographic direction, when the films are deposited at 500, 600 and 700 ℃, respectively. As the deposition temperature increases, the CBN films undergo (115)-(200)-(00l) orientation transition. Meanwhile, SEM results show that 600 ℃ is the optimal deposition temperature for high-quality a-axis epitaxial growth of CBN films on MgO substrates. Under this condition, the films are well bonded to the substrate with a low roughness. HRXRD and HRTEM analyses show that the (200)-oriented CBN films are heterogeneous epitaxial growth, forming a semiconformal lattice interface between the (200)-oriented CBN film and the MgO substrate, also revealing a crystallographic relationship between the as-grown thin film and the substrate, i.e., (100)[001]CBN//(100)[001]MgO. The average (200) spacing at the CBN/MgO interface was measured to be 0.5312 nm. Based on the lattice-matching relationship, a theoretical model is proposed that four CBN unit cells matching five MgO unit cells. Moreover, the nanodomain structure of the (115)-oriented CBN thin films and the out-of-plane polarization switching of the (200)-oriented CBN thin films are demonstrated by PFM.

Piezoelectric multilayer actuators feature large displacement generation at a relatively low driving voltage and are widely used in various fields. As the most commonly used material in multilayer actuators, soft lead zirconate titanate (PZT) ceramics have higher dielectric constant and loss, which often lead to higher power consumption and heat generation that in turn affect fatigue characteristics and stability of piezoelectric multilayer actuators. In this work, Mn-doped (in mole fraction) Pb(Sb_1/2Nb_1/2)_0.02Zr_0.51Ti_0.47O₃-0.6%MnCO₃ (PSN-PZT) hard ceramic was selected as base material in order to prepare piezoelectric ceramics that have low heat generation and are suitable for the application of piezoelectric multilayer actuator. Certain amount of Li₂CO₃ was doped as sintering aid for lowering sintering temperature of ceramics, and above-Curie-temperature polarization was utilized to enhance electric properties of ceramics. Eventually, multilayer actuator composed of this material was fabricated via tape-casting process and compared with Pb(Mg_1/3Nb_2/3)_0.25(Ti_0.48Zr_0.52)_0.75O₃ (PMN-PZT) actuator prepared with the same parameters. The results indicated that the sintering temperature of PSN-PZT ceramic was decreased to 1050 ℃ due to Li₂CO₃ sintering aid, which introduced liquid sintering during the sintering process. PSN-PZT ceramics poled above the Curie temperature obtained optimal electric performance with 0.1% (in mass) Li₂CO₃ doping, and the piezoelectric coefficient (d₃₃) and unipolar strain at 2 kV/mm reached 388 pC/N and 0.13%, respectively. The results of temperature rise and strain degradation of both multilayer actuators indicated that the temperature rise of hard PSN-PZT actuator was about 20 ℃ lower than that of PMN-PZT actuator under 200 Hz and the strain decreased by 6% after 5×10⁶ cycles. It indicates that PSN-PZT ceramics with Li₂CO₃ doping for lowering sintering temperature have some advantages in heat generation and fatigue characteristic while having descent piezoelectric properties, which endows it an important potential application in high-power, high-frequency and other demanding working conditions.

(Ba,Ca)(Ti,Sn)O₃ (BCTS) piezoelectric ceramics exhibit excellent piezoelectric properties and show great potential in the fields of piezoelectric sensors and transducers. However, their sintering temperature is very high, typically exceeding 1450 ℃, which limits their practical applications. In order to lower the sintering temperature, the oxide CuO was added into (Ba_0.95Ca_0.05)(Ti_0.90Sn_0.10)O₃ ceramics as a sintering aid in this work. Herein, BCTS-xCuO piezoelectric ceramics were prepared by the conventional solid-state sintering method, and the influence of CuO content on the sintering temperature, structure as well as dielectric and piezoelectric properties of BCTS ceramics was investigated systematically. After adding CuO, the perovskite crystal structure was mainly formed in BCTS ceramics, with a small amount of secondary phases, which may be Ba₂TiO₄ and Ba₂Cu₃O_5.9. Moreover, it was found that CuO doping can effectively reduce the sintering temperature of ceramics from 1480 ℃ to 1360 ℃ and improve the relative density of piezoelectric ceramics. The highest relative density (98.7%) and maximum average grain size (22.5 μm) were obtained at x=0.03. Hence, the optimal electrical properties were obtained at x=0.03 with piezoelectric coefficient d₃₃=573 pC/N, planar electromechanical coupling coefficient k_p=36%, relative permittivity ε_r=9467, and dielectric loss tanδ=0.021. Compared with other reported low-temperature sintered BaTiO₃-based ceramics, the x=0.03 component ceramics in this study obtained higher d₃₃ at a low sintering temperature, showing excellent comprehensive properties. In conclusion, this work demonstrates that CuO doping can successfully reduce the sintering temperature and optimize the piezoelectric properties of BCTS ceramics.

As a kind of important functional material, flexible piezoelectric materials can realize the effective conversion between mechanical energy and electrical energy, with the advantages of good toughness, high plasticity and light weight. Therefore, they can be attached to the human body to obtain human or environment information in real time, which is widely used in the fields of motion detection, health monitoring, and human-computer interaction. Due to high requirements of various three-dimensional (3D) structures of the flexible piezoelectric materials, additive manufacturing has been extensively utilized to fabricate different kinds of piezoelectric materials. This technology is expected to break the bottleneck of traditional processing of piezoelectric material by improving the structural design freedom and the performance of flexible piezoelectric materials, and provides enormous potential and opportunities for the application of flexible piezoelectric materials. Based on the introduction of the classification and features of flexible piezoelectric materials, this paper explained the main additive manufacturing technologies, including fused deposition modeling, direct ink writing, selective laser sintering, electric-assisted direct writing, stereolithography, and inkjet printing that commonly used in processing these materials. Then, various structural designs, such as multi-layer structure, porous structure, and interdigital structure for the flexible piezoelectric materials produced by different additive manufacturing approaches were reviewed. Moreover, the applications of additive manufactured flexible piezoelectric materials in energy harvesting, piezoelectric sensing, human-computer interaction, and bioengineering were introduced. Finally, the challenges faced by additive manufacturing on processing flexible piezoelectric materials and the development trends in the future were summarized and prospected.

Wearable instruments are functional devices that can be worn on human body, sensing, transmitting and processing body or environmental information in real time, and show broad application prospects in medical health, especially artificial intelligence, sports and entertainment. With the development of wearable instruments, various flexible sensors have emerged. Flexible mechanical sensors based on piezoelectric effect have attracted much attention because of their advantages of wide sensing frequency, fast response, good linearity, and self-power supply. However, traditional piezoelectric materials are mostly brittle ceramics and crystalline materials, which limit their application in flexible devices. With the deepening of research, more and more flexible piezoelectric materials and piezoelectric composites continue to emerge, injecting new development vitality into flexible wearable mechanical devices. This article mainly summarizes the cutting-edge progress of flexible wearable piezoelectric devices, including piezoelectric principle, preparation and performance improvement methods of flexible piezoelectric materials. In addition, the main application directions of flexible wearable piezoelectric devices, including medical health and human-computer interaction, as well as the challenges and opportunities encountered, are summarized.

Calcium bismuth niobate (CaBi₂Nb₂O₉) is a typical bismuth layered structure piezoelectric material with high Curie temperature (about 943 ℃) and high stability, which is an important candidate functional element for high temperature vibration sensors above 600 ℃. However, its low piezoelectric coefficient and high temperature resistivity seriously limit the signal acquisition of high-temperature piezoelectric vibration sensor. To improve the comprehensive performance, in this work, W/Cr co-doped CaBi₂Nb_1.975W_0.025O₉-x%Cr₂O₃ (CBNW-xCr, 0<x≤0.2) Aurivillius phase ceramics were prepared via conventional solid-state sintering route. The effects of W/Cr co-doping on the crystal structure and electrical properties of CBN piezoelectric ceramics were investigated. The results show that co-doping of W/Cr elements transforms crystal structure of the ceramics from orthorhombic to tetragonal crystal system, enhances distortion of the crystal structure, and significantly improves piezoelectric and insulating properties of the piezoelectric ceramics. When x=0.1, the Curie temperature is 931 ℃, the piezoelectric coefficient is 15.6 pC/N, the resistivity reaches the order of 10⁶ Ω∙cm at 600 ℃, and the dielectric loss is only 0.029, which endows the system an important potential application in the field of high-temperature piezoelectricity.

Antiferroelectric (AFE) materials exhibit great potential in the application of high-performance dielectric energy storage capacitors due to their electric field-induced AFE-ferroelectric (FE) phase transition. However, the large hysteresis of field-induced phase transition makes it difficult to simultaneously achieve high energy-storage density (W_rec) and efficiency (η) for AFEs. This work improved the energy-storage performance of NaNbO₃-based lead-free AFE ceramics by introducing the third group Bi(Mg_0.5Ti_0.5)O₃ into 0.76NaNbO₃-0.24(Bi_0.5Na_0.5) TiO₃ to regulate its relaxation characteristics. Novel lead-free AFE ceramics, (0.76-x)NaNbO₃-0.24(Bi_0.5Na_0.5)TiO₃-xBi(Mg_0.5Ti_0.5)O₃, were prepared by a traditional solid-state reaction method. Their phase structure and microstructure as well as dielectric, energy-storage, and charge-discharge characteristics were studied. The results indicated that introduction of Bi(Mg_0.5Ti_0.5)O₃ obviously enhanced the dielectric relaxor behavior of the matrix without changing its AFE R-phase structure, which led to the significantly reduced polarization hysteresis. Especially, a linear-like polarization-field hysteresis loop with extremely-low hysteresis was obtained in the composition of x=0.050. At the same time, microstructure of the ceramic was effectively optimized, its dielectric constant decreased, and its breakdown strength had significant enhanced. As a result, a high W_rec=3.5 J/cm³ and a high η=93% were simultaneously achieved under a moderate electric field of 30 kV/mm in the x=0.050 ceramic. Moreover, the x=0.050 ceramic also exhibited excellent charge-discharge characteristics with a high-power density P_D=131(1±1%) MW/cm³, a high discharge energy density W_D=1.66(1±6%) J/cm³ and a fast discharge rate t_0.9<290 ns at 20 kV/mm. The charge-discharge properties maintained good stability within a wide temperature range of 25-125 ℃. These results indicate that 0.71NaNbO₃-0.24(Bi_0.5Na_0.5)TiO₃-0.050Bi(Mg_0.5Ti_0.5)O₃ ceramics can be expected to be applied in high-power energy-storage capacitors.

Dielectric thin film, one of the materials of which storage energy in the form of electrostatic field via dielectric polarization, can be widely used in electric equipment, due to their high power density and high charge/ discharge efficiency. Currently, the dielectric energy storage films perform lower energy density and weak temperature stability. In this work, 0.9BaTiO₃-0.1Bi(Mg_1/2Ti_1/2) O₃(0.9BT-0.1BMT) ferroelectric thin films were prepared via a Sol-Gel method on Pt/Ti/SiO₂/Si substrates and annealed in the range of 700-900 ℃ to realize high energy storage density and wide-temperature stability by introducing BMT. The effect of annealing temperature on phase composition and microstructure was investigated. The results show that denseness of thin films reduce obviously when the annealing temperature is over 750 ℃ and their grain size increases gradually with the increase of treatment temperature. Additionally, the thin films annealed at 750 ℃ display optimized comprehensive feature: room-temperature dielectric constant of ~399, loss tangent of ~5.79% at 1 kHz, and ∆C/C_{25 ℃} ratio only within ±13.9%. Meanwhile, relaxor value, γ≈1.96 calculated according to Currie-Weiss law consolidates that the thin films possess obvious relaxor characteristics. Results of energy storage shows that the max value of W_rec is ~ 51.9 J/cm³, and the τ_0.9 is below 15 μs at pulse charge measure. Moreover, results of temperature stability measurement show W_rec>20 J/cm³, η>65% (1600 kV/cm) and τ_0.9<7.2 μs from room temperature to 200 ℃, demonstrating that the film still exists high and stable energy storage under high temperature. Therefore, the ferroelectric thin film 0.9BT-0.1BMT prepared in this work has a promising applications in energy storage under high temperature environment.

In recent years, pressure sensors have been widely applied in the fields of smart wearable textile, health detection, and electronic skin. The emergence of the two-dimensional nanomaterial MXene has brought a brand-new breakthrough for pressure sensing. Ti₃C₂T_x is the most popular studied MXene in the field of pressure sensing and shows good mechanical, electrical properties, excellent hydrophilicity, and extensive modifiability, enabling it an ideal material for pressure sensing. Hence, researchers have conducted a lot of explorations and studies on design and application of MXene in pressure sensors in recent years. Herein, the preparation technologies and antioxidant methods are summarized. Design of MXene-based microstructures is also introduced, including aerogels/porous structural materials, hydrogels, flexible substrates, and films, which are beneficial to improve the response range, sensitivity, and flexibility of pressure sensors, and promote the rapid development of pressure sensors. The mechanisms of MXene pressure sensors are further broached, including piezoresistive, capacitive, piezoelectric, triboelectric, battery typed and nanofluidic. MXene has been applied in a wide range of sensors for various mechanisms due to its excellent characteristics. Finally, the chance and challenge in the synthesis, properties, and pressure sensing performance of MXene materials are prospected.

Development of 5 G wireless communication and low-frequency radar detection has made low- frequency electromagnetic wave radiation a serious problem today. Although research on medium and high frequency band absorbing materials is now relatively mature, designing low frequency band absorbing materials remains a major challenge. Here, we designed a low-band composite absorbing material of 0.5-3 GHz based on the quarter-wavelength cancellation mechanism. A CIPs@Mn_0.8Zn_0.2Fe₂O₄-CNTs ternary composites were prepared by using a simple one-step hydrothermal method, which involved growing ferrite on the surface of carbonyl iron powder and carbon nanotubes. The influence of carbon nanotube content on the absorption peak frequency of the material was investigated. Experimental results show that carbon nanotubes enhances the material's attenuation coefficient by introducing additional interfacial polarization, dipole polarization and other loss mechanisms. Furthermore, coupling of high dielectric and high permeability enables the material to achieve better impedance matching in the low frequency band based on the quarter-wavelength cancellation mechanism. At a thickness of 4 mm, the reflection loss of the samples was obtained at 2.11 GHz and 1.75 GHz, with a -10 dB bandwidth of 1.70-2.70 GHz and 1.40-2.20 GHz, respectively. The composites exhibit excellent low-frequency absorption performance, endowing it highly suitable for applications helped by its simple preparation process and well low-frequency absorption. This research provides a new method for developing more effective low-frequency absorbing materials.

Antiferroelectric materials have been extensively studied in the field of dielectric energy storage due to their ultra-high power density. Lead zirconate (PbZrO₃, PZO), as a prototype of antiferroelectric material, has been one of the most studied antiferroelectric materials, and research on enhancing energy storage performance of PZO-based materials is a hotspot of the current study. In this work, further improvement of the energy storage performance of PZO-based antiferroelectric thin films was realized by further doping small-radius Sr²⁺ into the A-site of the PZO perovskite structure on the basis of La³⁺-doped PZO. A series of antiferroelectric thin films of A-site La/Sr co-doped Pb_0.94-xLa_0.04Sr_xZrO₃ (Sr-PLZ-x, x = 0, 0.03, 0.06, 0.09, 0.12) were prepared by Sol-Gel method, and the effects of Sr²⁺ doping on the crystal structure and electrical properties such as ferroelectricity, energy storage, and fatigue properties of Sr-PLZ-x antiferroelectric films were systematically investigated. The results show that with the doping of Sr²⁺, the lattice constants are gradually reduced, and the saturation polarization of the films is first slightly increased and then maintained, but finally gradually decreased. The tolerance factors of Sr-PLZ-x films are reduced with increasing Sr²⁺ doping content, while the antiferroelectricities of the films are enhanced. Both the switching field and the breakdown strength are increased, resulting in an improved energy storage performance of Sr-PLZ-x films. At x=0.03, the energy storage performance of Sr-PLZ-x antiferroelectric film reaches the highest, with the energy storage density and efficiency are 31.7 J/cm³ and 71%, respectively. Meanwhile, the doping of Sr²⁺ also makes the fatigue characteristics of Sr-PLZ-x antiferroelectric films further improved. The x=0.12 antiferroelectric film exhibits only 3.4% and 2.7% degradation in energy storage density and energy storage efficiency after 10⁷ cycles. In summary, the method of A-site La/Sr co-doping can effectively improve the energy storage performance of PZO-based antiferroelectric films.