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Flash sintering is arousing growing interest because high-density ceramics can be obtained at lower temperatures and shorter dwell times than conventional sintering. However, not only temperature and dwell times should be controlled during flash sintering but also parameters such as the electric field and electric current should be considered. Controlling all the parameters during the processing allows comprehensive control of the microstructure and, consequently, functional properties can be improved. In this work, it is evidenced that an exhaustive control of the flash electric current is a crucial factor for tailoring the microstructure of BaTiO3 ceramics. The results reveal that the most suitable way to control the sintering process is by using non-linear current profiles because better densification and improved grain growth is achieved. Although the results focus on BaTiO3, this work offers a new pathway to tailor the microstructure of flash sintered ceramics, which may be extended to other materials.

Sub-10 nm ferroelectric and multiferroic materials are attracting increased scientific and technological interest, owing to their exciting physical phenomena and prospects in miniaturized electronic devices, neuromorphic computing, and ultra-compact data storage. The Bi6Ti2.9Fe1.5Mn0.6O18 (B6TFMO) Aurivillius system is a rare example of a multiferroic that operates at room temperature. Since the formation of magnetic impurity phases can complicate attempts to measure ferromagnetic signal intrinsic to the B6TFMO multiferroic phase and thus limits its use, herein we minimize this by utilizing relatively large (49%) bismuth excess to counteract its volatility during sub-10 nm growth. X-ray diffraction, electron microscopy, and atomic force microscopy show sample crystallinity and purity are substantially improved on increasing bismuth excess from 5 to 49%, with the volume fraction of surface impurities decreasing from 2.95–3.97 vol% down to 0.02–0.31 vol%. Piezoresponse force microscopy reveals 8 nm B6TFMO films are ferroelectric, with an isotropic random distribution of stable in-plane domains and weaker out-of-plane piezoresponse. By reducing the volume fraction of magnetic impurities, this work demonstrates the recent progress in the optimization of ultra-thin B6TFMO for future multiferroic technologies. We show how the orientation of the ferroelectric polarization can be switched in 8 nm B6TFMO and arrays can be “written” and “read” to express states permitting anti-parallel information storage.

Ferroelectric field-effect transistor-based circuit implementation mimicking FitzHugh-Nagumo neuron is proposed in this work. The proposed circuit is shown to mimic biological neuron properties such as excitation block and anodal break excitation which are not mimicked by an integrate and fire neuron model. We also show a winner-take-all circuit that can be used with this proposed neuron implementation. The neuron implementation requires just one ferroelectric field-effect transistor, three baseline field-effect transistors, and one capacitor, making it area and energy-efficient. The neuron circuit, with minimum sized transistors, consumes approximately 10pJ per spike. The neuron’s energy consumption per spike can be reduced to as low as 100fJ by designing some of the transistors with aspect ratio less than one.

Ferroelectric HfO2-based materials hold great potential for widespread integration of ferroelectricity into modern electronics due to their robust ferroelectric properties at the nanoscale and compatibility with the existing Si technology. Earlier work indicated that the nanometer crystal grain size was crucial for stabilization of the ferroelectric phase of hafnia. This constraint caused high density of unavoidable structural defects of the HfO2-based ferroelectrics, obscuring the intrinsic ferroelectricity inherited from the crystal space group of bulk HfO2. Here, we demonstrate the intrinsic ferroelectricity in Y-doped HfO2 films of high crystallinity. Contrary to the common expectation, we show that in the 5% Y-doped HfO2 epitaxial thin films, high crystallinity enhances the spontaneous polarization up to a record-high 50 µC/cm2 value at room temperature. The high spontaneous polarization persists at reduced temperature, with polarization values consistent with our theoretical predictions, indicating the dominant contribution from the intrinsic ferroelectricity. The crystal structure of these films reveals the Pca21 orthorhombic phase with a small rhombohedral distortion, underlining the role of the anisotropic stress and strain. These results open a pathway to controlling the intrinsic ferroelectricity in the HfO2-based materials and optimizing their performance in applications.

To upgrade the electric properties of lead-free piezoceramics, (1–x)(Ba0.98Ca0.02Ti0.94Sn0.04Zr0.02)O3-xY2O3 (abbreviated as (1–x)BCTSZ-xY, x = 0 mol%, 0.02 mol%, 0.04 mol%, 0.06 mol%, 0.08 mol% and 0.1 mol%) ceramics were successfully synthesized by traditional solid-state sintering method. The phase structure and microstructure of ceramics were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and piezoresponse force microscopyeramics (PFM). The electric properties of ceramics were researched through piezoelectric, dielectric and ferroelectric test instruments. The results show that all samples have pure perovskite structure and favorable electric properties. The optimal electric properties which especially include superior ferroelectric properties are gained when Y2O3 content is 0.06 mol% (d33 = 419 pC/N, kp = 52%, Tc = 89.5 °C, er = 26900, tanδ = 2.86%, Pr = 14.41 μC/cm2, Ec = 1.8 kV/cm). Moreover, the temperature-dependent dielectricity of samples shows apparent relaxor behavior under different frequencies. The Curie–Weiss law further proves that all samples are typical relaxor ferroelectrics, and the relaxor degree of samples decreases with increase of Y2O3 content. In conclusion, Y2O3 plays a significant role in enhancing electric properties of BCTSZ ceramics.

A new approach for the stabilization of the ferroelectric orthorhombic ZrO2 films is demonstrated through nanosecond laser annealing (NLA) of as-deposited Si/SiOx /W(14 nm)/ZrO2 (8 nm)/W(22 nm), grown by ion beam sputtering at low temperatures. The NLA process optimization is guided by COMSOL multiphysics simulations. The films annealed under the optimized conditions reveal the presence of the orthorhombic phase, as confirmed by X-ray diffraction, electron backscatter diffraction, and transmission electron microscopy. Macroscopic polarization-electric field hysteresis loops show ferroelectric behavior, with saturation polarization of 12.8 µC cm-2 , remnant polarization of 12.7 µC cm-2 and coercive field of 1.2 MV cm-1 . The films exhibit a wake-up effect that is attributed to the migration of point defects, such as oxygen vacancies, and/or a transition from nonferroelectric (monoclinic and tetragonal phase) to the ferroelectric orthorhombic phase. The capacitors demonstrate a stable polarization with an endurance of 6.0 × 105 cycles, demonstrating the potential of the NLA process for the fabrication of ferroelectric memory devices with high polarization, low coercive field, and high cycling stability.

Optical control of functional properties in ferroic materials is now a highly appealing topic because it may entail different paradigms for future technologies. In ferroelectrics, in particular, controlling the properties with light implies noncontact external control of the material’s functionality, thereby opening a pathway for developing the next generation of photocontrolled devices. Recently, experimental observations have demonstrated that the dielectric permittivity of charged-domain-wall ferroelectrics can be easily modulated by visible light. However, because of the wide band gap of ferroelectric materials, the physical origin of this phenomenon is still controversial. Here, the photoinduced electronic reconstruction mechanism is proposed as the primary light-absorption mechanism in charged domain walls, allowing an understanding of the origin of the visible-light control of dielectric permittivity in ferroelectric materials.

Ferroelectric polymer poly(vinylidene fluoride) (PVDF) shows excellent electro-activity and is promising for flexible electronic devices. However, the processing of PVDF into the favourable ferroelectric structure (β-phase) presents difficulties, while its copolymer with trifluoroethylene (PVDF-TrFE) can directly crystallize into β-phase, but shows limited thermal stability and high-cost processing. As a result, an easily implementable method, pressing-and-folding (P&F), was used to produce highly compatible blended films of PVDF and PVDF-TrFE without using any hazardous solvent or complex polymer processing equipment. Hot-pressed PVDF (molecular weight: 530 kg/mol) and PVDF-TrFE (molar ratio: 51/49) films were firstly stacked before undergoing P&F treatment. Compared to extrusion-blended films before and after P&F, the P&F stacked films showed isotropic crystalline structure of β-phase, as confirmed using X-ray diffraction and infrared spectroscopy. The ferroelectric remnant polarization of the P&F stacked films is 0.068 C/m2, surpassing pure PVDF-TrFE (0.062 C/m2) and the simulated value of remnant polarization of pure PVDF (～0.065 C/m2). The above findings promise to provide inspirations for new processing strategy on PVDF based functional polymers.

Off-stoichiometry of perovskite structural Bi0.5Na0.5TiO3 (BNT) ferroelectrics can give rise to considerable oxide-ion conductivity. The inherent structural characteristics are urgent to be resolved due to its particular sensitivity of the conduction mechanism to the nominal composition and synthesis process. Herein, a thorough study of the temperature-dependent neutron, X-ray diffraction and Raman spectrum is carried out on a series of equivalently substituted A-site deficient non-stoichiometric and pristine BNT. Phase transition and defect association are systemically investigated in these dominated rhombohedral phases at room temperature, associated with well saturated ferroelectric states. Significant structural evolution identified by Rietveld refinements and the origin of the electrical performance are clarified at elevated temperatures, focusing on the subtle distortions of ionic displacements, oxygen octahedral tilts and local chemical environments for oxygen vacancies. The ion migration ability mediated by oxygen vacancies that are not energetically favorable in BNT mainly depends on the external substitutional disorder, and is strongly affected by the dopant concentration. Together with the lone pair substitution concept, superior oxide ionic conductivity is achieved, and an alternative strategy is provided in designing BNT based oxide ion conductors.

NaNbO3-based ceramics usually show ferroelectric-like P-E loops at room temperature due to the irreversible transformation of the antiferroelectric orthorhombic phase to ferroelectric orthorhombic phase, which is not conducive to energy storage applications. Our previous work found that incorporating CaHfO3 into NaNbO3 can stabilize its antiferroelectric phase by reducing the tolerance factor (t), as indicated by the appearance of characteristic double P-E loops. Furthermore, a small amount of MnO2 addition effectively regulate the phase structure and tolerance factor of 0.94NaNbO3-0.06CaHfO3 (0.94NN-0.06CH), which can further improve the stability of antiferroelectricity. The XRD and XPS results reveal that the Mn ions preferentially replace A-sites and then B-sites as increasing MnO2. The antiferroelectric orthorhombic phase first increases and then decreases, while the t shows the reversed trend, thus an enhanced antiferroelectricity and the energy storage density Wrec of 1.69 J/cm3 at 240 kV/cm are obtained for 0.94NN-0.06CH-0.5%MnO2(in mass fraction). With the increase of Mn content to 1.0% from 0.5%, the efficiency increases to 81% from 45%, although the energy storage density decreases to 1.31 J/cm3 due to both increased tolerance factor and non-polar phase.

Nowadays, photovoltaic effect has been widely studied in various ferroelectric materials due to its applications as optoelectronic devices. In this work, with BiFeO3 (BFO) films as the photovoltaic materials, we report the effects of Eu3+ doping content on the phase structure, ferroelectric and optical properties of BFO films grown on Ca0.96Ce0.04MnO3/YAlO3 (001) substrate. We found that a small doping level of 0.05 could induce a phase change of BFO from tetragonal to rhombohedral, due to the shrinking of the lattice upon Eu3+ doping and the breaking of surface terrace structure induced by Ca0.96Ce0.04MnO3 layer. This results in a sharp band gap reduction from 3.30 eV to 2.60 eV, and a decrease in the coercivity of ferroelectric polarization switching. Based on these findings, we investigate the photovoltaic effects of ITO/EuxBi1-xFeO3/Ca0.96Ce0.04MnO3 vertical capacitors. It is found that the short-circuit current density (Jsc) decreases with increasing Eu3+ doping, whereas the open-circuit voltage (Voc) first increases to a level of 0.1 V and then decreases with further Eu3+ doping. This could be explained by the combined effect of Schottky-junction and depolarization field on the photovoltaic process. Our research suggests that a moderate Eu3+ doping is helpful for enhancing the photovoltaic effect of BFO thin film devices.

In this article, we explore the design of energy-efficient intermittently powered systems (IPSs) using reconfigurable-ferroelectric transistors (R-FEFETs). Utilizing the dynamic tunability between volatile and nonvolatile modes of operation in R-FEFETs, we design nonvolatile flip-flops (NVFFs) and memory (NVM) suitable for IPS. We present two variants of R-FEFET-based NVFFs (RNVFFs): 1) with automatic backup and 2) with need-based backup. While the former offers high backup energy efficiency, the latter offers low normal operation energy. We also present an IPS-specific R-FEFET-based NVM (3T-R) with high energy efficiency compared with FEFET-based 2T NVM. Leveraging these nonvolatile circuits, we map the microcontroller unit (MCU) core registers of an IPS to RNVFFs and its on-chip memory to 3T-R. Subsequently, we analyze system-level implications of improving NVFFs and NVM individually by using R-FEFETs compared with existing FEFET-based designs. Our system-level simulations demonstrate that although we improve the register energy by 55%-67%, the total memory and system-level energy savings obtained from just improving the NVFFs (registers) in the microcontroller core are only 0.60%-5.78% and 0.31%-3.18%, respectively. However, improving the NVM by using 3T-R results in a much larger total memory and system-level energy savings in the range of 37%-40% and 20%-22%, respectively, in the context of a state-of-the-art IPS.

Herein, Ag1-3xSmxNbO3 (0 ≤ x ≤ 0.025) antiferroelectric ceramics were successfully synthesized by solid state methods. The effect of Sm3+ doping on the structure, property and energy storage performance were studied. With the increasing Sm3+ concentrations, the average grain size decreased. Meanwhile, the stability of high temperature M phases (i.e., the structure between Tf and T3) was expanded, which led to low loss for energy storage. Both of structure analysis and ferroelectric tests revealed the existence of weakly polar/AFE-like phase below Tf. The Sm3+ doping tended to suppress the ferroelectric behavior and expand the stability of antiferroelectricity. Consequently, a significantly enhanced energy storage performance (Wrec = 3.8 J/cm3, η = 73 %) could be achieved in Ag0.97Sm0.01NbO3 ceramic, which was almost 1.5 times larger than that in non-doped AgNbO3 (Wrec = 2.4 J/cm3, η = 45 %) under the similar applied field of 1705 kV/cm ± . In particular, the performance of the ceramic showed great temperature stability with variation of ± 5 % from 25 °C to 125 °C. These results indicated that the Ag0.97Sm0.01NbO3 ceramic could be an ideal lead-free candidate used in the energy storage field.

Na1/2Bi1/2TiO3-based materials exhibit potential for applications in high-power ultrasonics. The composites of Na1/2Bi1/2TiO3-yBaTiO3 (NBTyBT; y denotes mole%) with ZnO inclusions were demonstrated to stabilize a ferroelectric equilibrium that led to enhanced thermal depolarization temperature (Td) and increased mechanical quality factor (Qm). This work addresses the influence of the matrix NBTyBT phase by investigating two limiting choices based on symmetry (tetragonal/rhombohedral) and polar (relaxor/ferroelectric) nature. While the composites constituting the tetragonal NBT9BT (non-ergodic relaxor at room temperature) matrix phase exhibit improved Td, the critical temperatures in the composites with rhombohedral NBT3BT (displaying spontaneous ferroelectric order at room temperature) exhibit only marginal changes. Further, NBT3BT composites feature a 45% increase in Qm, while the corresponding increase is roughly three-fold for the NBT9BT composites. A 3-D Finite Element Method is used to simulate the electric field gradient at the matrix/inclusion interface, with the effective field distribution estimated to be higher than the applied field for highly conducting ZnO inclusions. The electrical properties indicate that, while the deviatoric stress at the matrix/inclusion interface stabilizes the ferroelectric equilibrium for the relaxor matrix phase, the stresses disrupt the long-range order for the ferroelectric matrix phase. These results establish the volume-limit of the second phase to stabilize a ferroelectric equilibrium, in addition to substantiating the role of residual stress evidenced by changes in the polar nature. Finally, a comparison of the composites with different NBTyBT phases is presented, with NBT6BT:ZnO composites demonstrating an optimal increase in both Td and Qm.

BiFe1-2xZnxMnxO3 (BFZMO, with x = 0–0.05) thin films were synthesized via sol–gel method. Effects of (Zn, Mn) co-doping on the structure, ferroelectric, dielectric, and optical properties of BiFeO3 (BFO) films were investigated. BFZMO thin films exhibit rhombohedral structure. Scanning electron microscopy (SEM) images indicate that co-doping leads to a decrease in grain size and number of defects. Leakage current density (4.60×10−6 A/cm2) of BFZMO film with x = 0.02 was found to be two orders of magnitude lower than that of pristine BFO film. Owing to decreased leakage current density, saturated P–E curves were obtained. Maximum double remnant polarization of 413.2 μC/cm2 was observed for BFZMO thin film with x = 0.02, while that for the BFO film was found to be 199.68 μC/cm2. The reason for improved ferroelectric properties is partial substitution of Fe ions with Zn and Mn ions, which resulted in a reduction in the effect of oxygen vacancy defects. In addition, co-doping was found to decrease optical bandgap of BFO film, opening several possible routes for novel applications of these (Zn, Mn) co-doped BFO thin films.

In this work, we synthesized a novel and eco-friendly relaxor ferroelectric system, i.e., (1−x)(0.8Bi0.5Na0.4K0.1TiO3-0.2SrTiO3)-xNaNbO3 (BS-xNN) ceramics with x = 0.1–0.4 based on a solid state reaction technique. The structural, microstructural, dielectric as well as ferroelectric characteristics of BS-xNN ceramics were comprehensively examined. According to our findings, the Ti–O coupling reduces as the NN content increases, while the Nb–O coupling strengthens, leading in a nano-scale polarization mismatch-reestablishment process that enhances energy storage performance. Because of the reduction in thickness and porosity, the viscous polymer process significantly increases the breakdown strength of ceramic samples. More crucially, at 260 kV/cm, 0.6BS-0.4NN ceramics have an ultrahigh recoverable energy storage density Wrec of 4.44 J/cm3 and a high energy storage efficiency η of 81.8%. Furthermore, thermal stability of energy storage performance is also identified across a wide temperature range of 30 °C from 140 °C at 215 kV/cm. The higher performance of energy storage not only indicates the feasibility of our technique, but also serves as a model for the manufacturing of high-quality dielectric ceramics with a wide range of industrial applications.

Piezoelectric materials are widely used in electromechanical energy conversion, such as in sensors, transducers, and self-powered materials. In this paper, the influence of the Sm doping content on the microstructure and ferroelectric, piezoelectric, dielectric, and field-induced strain properties of 0.70Pb(Mg1/3Nb2/3)O3-0.30PbTiO3 (PMN-PT) ceramics was investigated. Sm-doped PMN-PT ceramics with both high piezoelectric properties (d33∼1406 pC/N) and a large electromechanical coupling coefficient (kp∼0.69) were synthesized. Based on their piezoelectric effect, a maximum output voltage of 31 V was achieved under external forces. The output voltages showed satisfactory stability, repeatability, and sensitivity under periodic external forces; hence, Sm-doped PMN-PT piezoelectric ceramics are potential candidates for energy conversion and signal monitoring.

This paper reports the improvement of electrical, ferroelectric and endurance of Hf0.5Zr0.5O2 (HZO) thin-film capacitors by implementing W electrode. The W/HZO/W capacitor shows excellent pristine 2Pr values of 45.1 μC/cm2 at ±6 V, which are much higher than those of TiN/HZO/W (34.4 μC/cm2) and W/HZO/TiN (26.9 μC/cm2) capacitors. Notably, the maximum initial 2Pr value of W/HZO/W capacitor can reach as high as 57.9 μC/cm2 at ±7.5 V. These strong ferroelectric polarization effects are ascribed to the W electrode with a fairly low thermal expansion coefficient which provides a larger in-plane tensile strain compared with TiN electrode, allowing for enhancement of o-phase formation. Moreover, the W/HZO/W capacitor also exhibits higher endurance, smaller wake-up effect (10.1%) and superior fatigue properties up to 1.5 × 1010cycles compared to the TiN/HZO/W and W/HZO/TiN capacitors. Such improvements of W/HZO/W capacitor are mainly due to the decreased leakage current by more than an order of magnitude compared to the W/HZO/TiN capacitor. These results demonstrate that capping electrode material plays an important role in the enhancement of o-phase formation, reduces oxygen vacancies, mitigates wake-up effect and improves reliability.

BiFeO3–BaTiO3–based solid solutions are promising candidates for high–temperature piezoelectric devices because of their high Curie temperature (TC) and considerable electrical properties. Here, we reported an optimum composition of 0.7Bi(Fe0.999Mn0.001)O3–0.3BaTiO3 ceramic with a large piezoelectric constant (d33) of 230 pC/N and a high TC of 505 °C, which was attributed to the intentional introducing of the ceramic with MnO and MnO2 mixture. Furthermore, an in situ d33 measurement was carried out, demonstrating excellent thermal stability for the 0.7Bi(Fe0.999Mn0.001)O3–0.3BaTiO3 specimen. The d33 remained above 200 pC/N in the temperature range of 25 °C–400 °C and its fluctuation was less than ± 15 %. It was determined that the high d33 in the 0.7BiFe0.999Mn0.001)O3–0.3BaTiO3 ceramic originated from a synergistic effect of rhombohedral distortion, intrinsic response, and ferroelectric order. The findings establish a solid correlation between electrical properties and phase/domain structure, and provide a novel approach to improve the piezoelectric properties for BiFeO3–BaTiO3–based ceramics.

BaTiO3 ceramics doped with double perovskite Sr2KMoO6 (BT-SKM) are fabricated via solid-state reaction technology. The effects of SKM dopants on the structure, band gap and electrical/magnetic properties of BT are systematically studied. XRD and Raman spectra analysis show polycrystalline perovskite structure of the samples, which confirms the structural changes. With the addition of SKM dopants, the grain size of the samples decreases significantly. The band gaps of doped BT samples reduce, and the minimum band gap of BT-SCM is 1.77 eV, which is apparently reduced compared with the band gap of pure BT of 3.22 eV. However, the ferroelectric properties are weakened in samples doped with SKM. This ascribes to the introduction of more oxygen vacancies by dopants, which impedes the switching of domains, resulting in deterioration of ferroelectric properties. Furthermore, ferromagnetism of BT-SNM is observed, which may be attributed to the long-range exchange interaction between Ni2+ ions and oxygen vacancies. These results reveal the potential applications of these perovskite oxides in photovoltaic and memory devices.

Recently, the anomalous photovoltaic effect of ferroelectric materials has attracted considerable attention in the construction of efficient solar cells owing to the above-bandgap photovoltage of these materials. In this study, we investigate the anomalous photovoltaic effect of relaxor-based ferroelectric Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIMN-PT) ceramics with large remnant polarization and a narrow optical bandgap. Excellent photovoltaic performance with an ultrahigh open-circuit voltage of 23 V (575 V/cm) is achieved, which is higher than the open-circuit voltages of all reported polycrystalline materials with similar thickness. The phase structure, microstructure morphology, domain structure, ferroelectric and optical characteristics are analyzed, which could provide clues to the origin of the ultrahigh open-circuit voltage of PIMN-PT ceramics. The results suggest that the relaxor-based ferroelectric PIMN-PT system is a potential candidate for photovoltaic solar energy conversion devices.

Owing to the complex composition architecture of these solid solutions, some fundamental issues of the classical (1−x)Bi1/2Na1/2TiO-xBi1/2K1/2TiO3 (BNT-xBKT) binary system, such as details of phase evolution and optimal Na/K ratio associated with the highest strain responses, remain unresolved. In this work, we systematically investigated the phase evolution of the BNT-xBKT binary solid solution with x ranging from 0.12 to 0.24 using not only routine X-ray diffraction and weak-signal dielectric characterization, but also temperature-dependent polarization versus electric field (P-E) and current versus electric field (I-E) curves. Our results indicate an optimal Na/K ratio of 81/19 based on high-field polarization and electrostrain characterizations. As the temperature increased above 100 °C, the x = 0.19 composition produces ultrahigh electrostrains (> 0.5%) with high thermal stability. The ultrahigh and stable electrostrains were primarily due to the combined effect of electric-field-induced relaxor-to-ferroelectric phase transition and ferroelectric-to-relaxor diffuse phase transition during heating. More specifically, we revealed the relationship between phase evolution and electrostrain responses based on the characteristic temperatures determined by both weak-field dielectric and high-field ferroelectric/electromechanical property characterizations. This work not only clarifies the phase evolution in BNT-xBKT binary solid solution, but also paves the way for future strain enhancement through doping strategies. © 2021 The Chinese Ceramic Society. This work was supported by the National Natural Science Foundation of China (Grant Nos. 51772239 and 51761145024 ) and the Fundamental Research Funds for the Central Universities ( XJTU ). The SEM work was done at International Center for Dielectric Research (ICDR), Xi'an Jiaotong University, Xi'an, China.

Recently, there is a surge of research interest in configurable ferroelectric conductive domain walls which have been considered as possible fundamental building blocks for future electronic devices. In this work, by using piezoresponse force microscopy and conductive atomic force microscopy, we demonstrated the controlled manipulation of various conductive domain walls in epitaxial BiFeO3 thin films, e.g. neutral domain walls (NDW) and charged domain walls (CDWs). More interestingly, a specific type of nanoscale domains was also identified, which are surrounded by highly conductive circular CWDs. Similar nanoscale domains can also be controlled created and erasured by applying local field via conductive probe, which allow nondestructive current readout of different domain states with a large on/off resistance ratio up to 102. The results indicate the potential to design and develop high-density non-volatile ferroelectric memories by utilizing these programable conductive nanoscale domain walls.

As microelectronic devices move toward integration and miniaturization, the thin film capacitors with high energy density and charge/discharge efficiency have attracted immense interests in modern electrical energy storage systems. Despite morphotropic phase boundary (Na0.8K0.2)0.5Bi0.5TiO3-based lead-free materials with outstanding ferroelectric and piezoelectric properties, while large ferroelectric hysteresis with high remanent polarization (Pr) hinder to improve energy storage capability. Here, novel lead-free relaxor-ferroelectric (RFE) thin film capacitors with high energy density are successfully prepared in (1-x) (Na0.8K0.2)0.5Bi0.5TiO3-xBa0.3Sr0.7TiO3 [(1-x)NKBT-xBST] systems. Introducing BST into the NKBT systems is expected to reduce remanent polarization (Pr) on account of coupling reestablishment of the polar nano-regions (PNRs) and improving the relaxation behavior. As a result, 0.6NKBT-0.4BST thin film exhibits high energy density (Wrec ∼ 54.79 J/cm3) together with satisfactory efficiency (η ∼ 76.42%) at 3846 kV/cm. The stable energy storage performances are achieved within the scope of operating temperatures (20–200 °C) and fatigue cycles (1-107 cycles). This work furnishes a new technological way for the design of high energy-density thin film capacitors.

With the development of energy-storage technology and power electronics industry, dielectric capacitors with high energy density are in high demand owing to their high power density. Especially for ferroic dielectrics (including ferroelectrics and antiferroelectrics) showing dipole moments in the perovskite unit cells, large dielectric response under electric fields makes them own outstanding potentials for achieving high energy-storage density. Particularly, destroying long-range ferroelectric/antiferroelectric ordering by enhancing compositional disorder is found to be effective for extremely improving energy-storage properties (both high recoverable energy-storage density and efficiency), because these macroscopic-nonpolar nanodomains are highly polarizable under strong external electric fields. Moreover, owing to the heterogeneous structure induced dielectric relaxation characteristics, excellent temperature stability can be achieved simultaneously. The recent developments of (anti)polar nanoregions with different possible local symmetries in various lead-free perovskite-structured dielectrics have been summarized in this review, together with the achieved energy-storage properties based on them. This review would provide a guidance for preparing high-performance energy-storage capacitors by local-structure engineering for next-generation pulse power applications.

Bi0.5Na0.5TiO3 (BNT)-based ceramics are one of the most promising lead-free ferroelectrics due to their high strain property. Compared to other chemical modifications, rare earth ions doping provides significant possibility to optimize the strain property of BNT-based ceramics. In this work, the effects of rare earth ions on phase structure, microstructure, and strain & electrostrictive properties of lead-free BNT-based ceramics were systematically investigated. Rare earth ions (i.e., La3+, Sm3+, Yb3+, Dy3+, and Nd3+) were selected as the doping ions. Introducing moderate La3+ ions can drive the ferroelectric state of BNT-based ceramics to nonergodic relaxor state or ergodic relaxor state. The enhanced strain response of ∼0.40–0.42% and high converse piezoelectric coefficient of ∼600–630 pm/V can be achieved under 60–70 kV/cm for La3+-doped ceramic with nonergodic relaxor state. Besides, the giant electrostrictive coefficient Q33 of ∼0.047 m4/C2 can be obtained for La3+-doped ceramic with ergodic relaxor state. Other rare earth ions also present the promotion effect on strain enhancement for BNT-based ceramics. This study affords a significant guidance to optimize strain and electrostrictive properties of BNT-based ceramics via rare earth ions doping.

This work investigates the effects of double ion substitution on the ferroelectric, electrochemical, dielectric and photocatalytic properties of Gd and Fe doped La1-yGdyNi1-xFexO3 nanoparticles (NPs). La1-yGdyNi1-xFexO3 was fabricated by facile micro-emulsion path and its properties were studied by thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman scattering, Fourier Transform of Infrared (FTIR), energy dispersive x-rays (EDX) techniques. It has a distorted rhombohedral shape with crystallite size within the range of 17–23 nm. The doped material has a spherical heterogeneous morphology, and its surface area increased with increased doping. The electrochemical (CV, EIS, and I-V), conductivity and dielectric (dielectric constant and low dielectric & tangent loss) properties of La1-yGdyNi1-xFexO3 were dependent on the contents of the dopants (Gd and Fe). The doped material had improved specific capacitance compared to the undoped LaNiO3 due to the synergistic effect of Gd and Fe on the doped materials. The conductivity of Gd and Fe doped LaNiO3 5.16 × 104 Sm−1 was enhanced compared to the undoped LaNiO3 3.52 × 10−2 Sm1. Furthermore, hysteresis loop was used to investigate the coercivity (Hc), saturation magnetization (Ms) and remanence (Mr) of the material. The Ms and Mr values were enhanced with the content of the dopants. The photocatalytic activity (PCA) of the material in degrading malachite green (MG) dye was studied. La1-yGdyNi1-xFexO3 NPs was able to degrade up to 96.4% of the dye under visible light irradiation in 50 min. La1-yGdyNi1-xFexO3 has remarkable dielectric, electrochemical, ferroelectric and photo-catalytic properties and have potential applications in microwave, electrical, electronic, energy storage devices. It is also an active photo-catalyst material for the removal/oxidation of toxic pollutants from the environment.

Doping modification is commonly used to improve the electrical properties of BaTiO3 (BT). In this study, the ((1-x)BT-x(Bi2O3–La2O3)) ceramics were synthesised to investigate the charge balance compensation mechanisms of BT ceramics co-doped with La2O3 and Bi2O3 as donors at A-site. The XRD results showed that a pseudo-cubic phase was formed by intruding dopants. The Raman spectroscopy revealed that the samples, which x = 0.10 and 0.16, had relatively more oxygen and titanium vacancies. After heat-treatment the samples in oxygen atmosphere, the dielectric constant of the sample with x = 0.10 was higher than that of the untreated, but for x = 0.16, it was almost no changed. These results indicated that the different charge balance compensation mechanism was exist in the samples with x = 0.10 and 0.16. Impedance measurements showed that the resistance tendency exhibited initial decrease and subsequent increase, leading to the electronic and ionic compensation mechanisms with x = 0.10 and 0.16, respectively. Ferroelectric properties also implied charge balance compensation mechanism transition, due to Ps and Pr were higher for x = 0.10 than for x = 0.16, respectively. This work provides a new strategy for modulating the electric properties of BT-based ceramics.

In this work, (K0.5Na0.5)NbO3–Sr(Bi0.5Nb0.5)O3: x wt% Er3+ (x = 0.1–0.4) transparent fluorescent ferroelectric ceramics were prepared using traditional solid-phase method. By solid solution of the second component Sr(Bi0.5Nb0.5)O3(SBN) and doped rare earth Er3+ to modify (K0.5Na0.5)O3(KNN), it was successfully prepared with good luminescence performance while maintaining ceramic samples with excellent light transmittance. Results show that the representative 0.94(K0.5Na0.5)NbO3-0.06Sr(Bi0.5Nb0.5)O3: 0.1 wt%Er3+ ceramic sample has a light transmittance of 80.25% in the near-infrared band (1100 nm). Meanwhile, in the visible light band (780 nm), the light transmittance is maintained at 71.95%. At the same time, the ceramic sample has good up-conversion luminescence performance, with two green light emissions and one red light emission at 525, 550 and 665 nm. The SEM photos show that the crystal grain size of the ceramic sample reaches the nanometer level with a fine and dense microstructure. The XRD pattern shows that the ceramic sample is in the pseudo cubic phase structure with the weakest optical anisotropy. In addition, the introduction of Bi3+ makes the ceramic samples significantly suppress Pr while maintaining a high Pmax, the ceramic samples have certain ferroelectric properties and good energy storage potential. This work has prepared an excellent multifunctional material, which provides helpful references for the development of opto-electronic materials.

Piezoelectric energy harvesting has attracted significant attention in recent years due to their high-power density and potential applications for self-powered sensor networks. In comparison to dense piezoelectric ceramics, porous piezoelectric ceramics exhibit superiority due to an enhancement of piezoelectric energy harvesting figure of merit. This paper provides a detailed examination of the effect of pore morphology on the piezoelectric energy harvesting performance of porous barium calcium zirconate titanate 0.5Ba(Zr0.2 Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 (BCZT) ceramics. Three different pore morphologies of spherical, elliptical, and aligned lamellar pores were created via the burnt-out polymer spheres method and freeze casting. The relative permittivity decreased with increasing porosity volume fraction for all porous BCZT ceramics. Both experimental and simulation results demonstrate that porous BCZT ceramics with aligned lamellar pores exhibit a higher remanent polarization. The longitudinal d33 piezoelectric charge coefficient decreased with increasing porosity volume fraction for the porous ceramics with three different pore morphologies; however, the rate of decrease in d33 with porosity is slower for aligned lamellar pores, leading to the highest piezoelectric energy harvesting figure of merit. Moreover, the peak power density of porous BCZT ceramics with aligned lamellar pores is shown to reach up to 38 μW cm-2 when used as an energy harvester, which is significantly higher than that of porous BCZT ceramics with spherical or elliptical pores. This work is beneficial for the design and manufacture of porous ferroelectric materials in devices for piezoelectric energy harvesting applications.

A correlation between piezoelectricity and photoluminescence is investigated for europium doped (Na0.41K0.09Bi0.5)TiO3 ceramic. An optimum piezoelectric and dielectric response is observed for 1.0 at.% Eu doped (Na0.41K0.09Bi0.5)TiO3. For doping concentration higher than 1.0 at.% a gradual fall in the piezoelectric response is observed which is associated to the amphoteric nature of Eu3+ ion. On the contrary, the photoluminescence intensity increases monotonically with the increase in Eu concentration. On application of an electric field, although there is no noticeable shift in the position and shape of the photoluminescence line, a quenching of hypersensitive 5D0 → 7F2 transition is observed. The quenching effect is more evident for lower doping concentration (less than 2.0 at.%) of europium. The emergence of irreversible tetragonal phase, after application of the electric field, is attributed to the quenching of 5D0 → 7F2 transition. Based on these investigations it is concluded that the piezoelectric and photo-luminescence lack one-to-one correlation. The PL response is associated to the local site symmetry around Eu3+ and it is independent of the development of long-range ordering.

In this work, the niobate-based borate glass-ceramic system K2O–Na2O–Nb2O5–B2O3 was proposed for the first time, in which the presence of alkali metal oxides not only tends to form ferroelectric crystalline phase to obtain high permittivity, but also optimizes the borate glass network structure to enhance the breakdown strength. The change of borate glass network structure and the influence on conductivity and carriers migrate is systematically discussed. The results show that the high breakdown performance is attributed to the transformation from [B∅2O−] triangle to [B∅4]- tetrahedron realizes the high extent of glass network polymerization, which effectively impedes carriers migration and reduces the conductivity. The high permittivity and low dielectric loss are obtained in the range of room temperature to 200 °C. Compared to other niobate-based glass-ceramics, the potassium sodium niobate borate glass-ceramic simultaneously achieve high discharge energy density, high power density and rapid discharge rate (∼14 ns).

Lead-based relaxor ferroelectric crystals, such as Pb(Mg1/3Nb2/3)O3-PbTiO3, are promising for functional applications due to their outstanding ferroelectric properties. Revealing ferroelectric domain structure and phase distribution at the nanoscale are important to understand the basic theory of ferroelectricity and promote their practical applications. In this study, the ferroelectric domain structure and atomic-scale phase distribution in a Pb(Mg1/3Nb2/3)O3 - 35 at.% PbTiO3 single crystal in the region of morphotropic phase boundary are systematically investigated by a combination of optical microscopy, scanning electron microscopy, and aberration-corrected transmission electron microscopy. It is found that 90° and 180° coarse domains are formed simultaneously in the ferroelectric single crystal. Moreover, there are tweed-like nano-domains formed inside each coarse single domain. Through careful investigations of distribution of stress and tetragonality, it is revealed that the tweed-like nano-domains are composed of nano-sized rhombohedral (R), monoclinic (M), and tetragonal (T) phases. The nano-scale T, M, R phases have the best, moderate, and lowest ferroelectricity, respectively.

An enormous study is being carried out in the field of emerging steep slope devices, specifically on negative-capacitance-based and phase transition-based devices. This article investigates the action of ferroelectric (FE) and phase transition material (PTM) on a hybrid device, negative-capacitance-assisted phase transition FinFET (NC-PT-FinFET). We encounter several unique phenomena resulting from this unified action and provide valid arguments based on these observations. A significant enhancement in the differential gain and transconductance, a unique variation in the effect of PTM on drain-channel coupling, tunability of hysteresis across PTM by FE thickness( [Formula: see text]), and ultralow subthreshold slope (SS) by lowering both of its factors are some of the major outcomes of the NC-PT-FinFET. Focus is built on comprehending the individual role of FE and PTM in the intriguing features observed in every device performance parameter with the help of mathematical expressions and physical interpretations. Various tunable parameters present in this hybrid device widen its applicability in digital and memory applications.

Ta-doped Bi3.25La0.75Ti3O12(BLTT)/ZnO films were fabricated on Pt(111)/Ti/SiO2/Si substrates by a magnetron sputtering method. Firstly, ZnO crystal thin films were grown on the substrates by a reactive sputtering method. Then, BLTT thin films were deposited on the ZnO layers at room temperature and post-annealed at 600 °C. The micromorphology, ferroelectric and dielectric properties of BLTT/ZnO films were analyzed. The XRD analysis shows that ZnO buffer layer significantly reduces the crystallization temperature of BLTT thin film. The TEM results show that lamellar BLTT grains are grown on ZnO layer at a certain angle with few elements diffusion at the interface of ZnO phase and Bi4Ti3O12 phase. The ferroelectric properties indicate that BLTT/ZnO films exhibit different remanent polarization and coercive fields under electric field with different directions. The novel mechanism of tailoring ferroelectric properties may open new possibilities for designing special ferroelectric devices.

By absorbing and transferring the photons (nearby bandgap) to photoelectrons, non–compensated (Ce4+ dopants) doping Bi5Ti3FeO15 ferroelectric films present switchable and stable photovoltaics. The defect dipole attraction in non–compensated doping films not only narrows the bandgap effectively by the creation of tunable intermediate sub–band (gap state), but enhances separation of electron–hole pairs in the visible–light region. The concept is proved by dramatic redshift of optical absorbance and intense photovoltaics. Subsequently, contrast investigations of equivalent–compensated doping films offer solid experimental evidences. Furthermore, the intensity of Coulomb attraction between defect dipoles can be destroyed by thermal perturbation, which is empirically supported by the abrupt drop of temperature dependent photovoltage at 340 K. These results demonstrate that non–compensated doping can be a promising route to construct more efficient energy transfer devices.

In this paper, a Junctionless Accumulation Mode Ferroelectric Field Effect Transistor (JAM-FE-FET) has been proposed and assessed in terms of RF/analog specifications for varied channel lengths through simulations using TCAD Silvaco ATLAS simulator, using the Shockley-Read-Hall (SRH) recombination, ferro, Lombardi CVT, fermi and LK models. Major analog metrics like transconductance (gm), intrinsic gain (AV), output conductance (gd), and early voltage (VEA) are obtained for the JAM-FE-FET arrangement. The proposed structure shows an improvement in parameters like gm, Ion/Ioff, Av, TGF by 6.82%, 27.95%, 5.2%, 38.83% respectively. Further, frequency analysis of the proposed device is performed and several critical RF parameters like fT, TFP, GFP, and GTFP have been observed to be enhanced by 6.89%, 11.38%, 13.65%, 12.01% respectively. Thus, the Junctionless accumulation mode ferroelectric FET (JAM-FE-FET) arrangement has been found to have superior analog and RF performance when compared to Junctionless ferroelectric FET(JL-FE-FET). As a result, the JAM-FE-FET device presented here can be contemplated a good contender for applications in high-frequency systems.

Ultrasonic stimulation induced polarization behaviors in ferroelectric materials have been extensively explored in catalytic degradations. However, the ultrasonic wave similarly can realize dye degradation by the sonocatalysis behavior, which is always neglected in most reports on in-situ ultrasound-induced piezoelectric catalysis, so that people might overestimate piezocatalytic contributions. For this, we designed a series of visible light sensitive bismuth layered ferroelectric materials (BLFMs), M0.5Bi2.5Nb2O9 (MBN, M = Li, Na, and K). It is found that the cavitation-induced degradation rates of Rhodamine B (RhB) strongly depend mechanical stirring speeds under a fixed ultrasonic power, which gradually increases with it, and reaches 77.9% (500 rpm and 3 h). Under lower stirring speed and reaction time (

The ferroelectric-metal field-effect transistor with recessed channel (RC-FeMFET) is proposed for one transistor dynamic random-access memory (1T-DRAM). Through technology computer-aided design (TCAD) simulations, the effects of inter-metal insertion on the FeFET with recessed channel (RC-FeFET) is identified. By evaluating electric field (e-field) across interlayer (IL) and memory window (MW), the improvements of program/erase cycling endurance and read current sensing margin (RSM) are verified in the RC-FeMFET. Moreover, considering program voltage (VW) and polarization switching time ( $\tau _{\mathrm{ p}}$ ), the guide line of the RC-FeMFET design is provided in terms of e-field across IL and MW for 1T-DRAM applications.

Relaxor-ferroelectric (RFE) ceramics possess slender ferroelectric hysteresis loop and low remnant polarization (Pr). They have great potential to provide excellent energy-storage performance as dielectric energy-storage materials. Herein, a lead-free 0.8Ba0.4Sr0.6TiO3–0.2Sr0.7Bi0.2TiO3 (0.8BST–0.2SBT) RFE ceramic with high energy-storage performance has been realized successfully. The addition of Bi3+ and increase in Sr2+content at the A site of the BST can effectively inhibit the growth of grains for high breakdown strength (Eb). As a result, an ultrafine average grain size of 0.7 μm was obtained in 0.8BST–0.2SBT RFE ceramic, affording a high Eb of 300 kV/cm. Further investigation revealed that the mutual conversion of short-range polar nanoregions and long-range-ordered ferroelectric domains upon application and withdrawal of a 300 kV/cm applied electric field resulted in a high maximum polarization (Pmax) of 31 μC/cm2 and a low Pr of 2.5 μC/cm2. Hence, the 0.8BST–0.2SBT RFE ceramic simultaneously exhibited a high recoverable energy-storage density of 3.3 J/cm3 and a high energy-storage efficiency of 85% at 300 kV/cm. Additionally, a good energy-storage performance was reported over a temperature range of 50°C-120 °C and frequency from 10 to 1000 Hz, making the 0.8BST-0.2SBT RFE ceramic a potential lead-free dielectric energy-storage material.

Ferroelectric thin/thick films with large electrocaloric (EC) effect are critical for solid state cooling technologies. Here, large positive EC effects with two EC peaks in a broad temperature range (∼100 K) were obtained in 0.95Pb0.92La0.08(Zr0.70Ti0.30)0.98O3-0.05BiFeO3 (BFO La-codoped PZT) epitaxial thin films deposited on the (100), (110) and (111) oriented SrTiO3 (STO) substrates by a sol-gel method. The thin film deposited on the (111) oriented STO substrate exhibited a stronger EC effect (∼20.6 K at 1956 kV/cm) near room temperature. However, the thin films deposited on the (100) and (110) oriented STO substrates exhibited a stronger EC effect (∼18.8 K at 1852 kV/cm and ∼20.8 K at 1230 kV/cm, respectively) around the peak of the dielectric permittivity (Tm, ∼375 K). Particularly, as the direction of the applied electric field was switched (E La-codoped PZT epitaxial thin films are promising candidates for application in the next solid-state cooling devices.

In this paper, for the first time, we explained a detailed physical insight for Negative Differential Resistance (NDR) to Positive Differential Resistance (PDR) transition in a ferroelectric-based negative capacitance (NC) FET and also its dependence on the device terminal voltages. Using extensive well-calibrated TCAD simulations, we have investigated this phenomenon on FDSOI NCFET. The NDR to PDR transition occurs due to Ferroelectric (FE) layer capacitance changes from a negative to positive state during channel pinch-off. This, in turn, results in a valley point in the output characteristic (IDS-VDS) at which the output resistance is infinite. We also found that we could alter the valley point location by modulating the vertical Electric field through the FE layer in the channel pinch-off region using body bias (VBB). The interface oxide charges also impacted the NDR to PDR transition, and a positive interface charge results in faster NDR to PDR transition. Further, we have utilized the modulation in NDR to PDR transition due to VBB for designing a current mirror. Results show that the output current (IOUT) variation due to VDS, reduces from ~8% to ~2% with VBB. We have also designed a single-stage common source (CS) amplifier and provided design guidelines to achieve a higher gain in the NDR region. The results obtained using a small-signal model of the FDSOI-NCFET demonstrate that ~25% higher gain can be achieved with the discussed design guidelines in the NDR region compared to the transition region of IDS-VDS. We have also explored the device scaling effect on the amplifier gain and found that ~2.23x gain can be increased with smaller channel length and higher device width.

Ferroelectric BaTiO3/ZnO heterojunction catalysts synthesised via the sol–gel method present obvious enhancements in spontaneous polarisation-driven Fenton-like catalytic activity. In this study, the oxidative decomposition of methylene blue (MB) dye was used as a model reaction. Pure BaTiO3-activated potassium monopersulphate (PMS) could decompose up to 48% of MB dye in an aqueous solution after 40 min. MB degradation rate firstly increased and then decreased as the ZnO content of the ferroelectric BaTiO3/ZnO heterojunction materials was increased. The maximum degradation rate of 100% and good cycling stability were observed when the BaTiO3:ZnO molar ratio was 1:1. Three active species, namely, holes (h+), sulphate radicals (SO4•−) and hydroxyl radicals (OH•), were produced following the spontaneous polarisation-driven catalytic degradation of the dye. Amongst these species, h+ and SO4•− were the main active species. Enhancements in the Fenton-like catalytic activity of BaTiO3/ZnO may be attributed to the formation of semiconductor heterojunctions, which could improve the spontaneous polarisation strength of ferroelectric BaTiO3, promote the effective separation of e−–h+ pairs and accelerate PMS activation. In summary, a novel PMS activation method was developed to provide a nontoxic, efficient and environmentally friendly technology for the degradation of organic pollutants.

Aurivillius ferroelectrics, Ca0.92-x(Na0.5Bi0.5)x(Na0.5Ce0.5)0.08Bi2Ta2O9 (CNCBT-NBT100x, x = 0, 0.02, 0.04, 0.06, 0.08, 0.10, 0.20, 0.30 and 0.40) ceramics were prepared by conventional electroceramic processing procedures. The novel Aurivillius ferroelectrics possess a gradual improving piezoelectricity (d33max∼12.8 pC/N) and ferroelectricity (Prmax∼7.4 μC/cm2) with the introduction of (Na0.5Bi0.5)2+ content. Moreover, the addition of (Na0.5Bi0.5)2+ also improves the temperature stability of piezoelectric activity obviously. The d33 of CNCBT-NBT40 maintains 94% of its initial stage even the annealing temperature reaching at 900 °C. The TC of CNCBT-NBT100x exhibits a decreasing trend with the increasing doping concentration, but CNCBT-NBT40 still possesses a high TC (TC∼924.9 °C). The high-temperature electrical resistivity of CNCBT-NBT100x almost remains unchanged owing to the close band-gap energy, and the ρ of CNCBT-NBT40 is above 6 × 106 Ω∙cm at 600 °C. This work may provide a new way of designing the doping formula to improve comprehensive properties of Aurivillius ferroelectrics.

Piezo-/ferroelectrics are essential materials for electromechanical sensors and actuators and energy harvesters in a wide range of technological applications. The demand for piezo-/ferroelectric materials with high Curie temperature (TC) arises from numerous emerging applications such as downhole oil and gas explorations, automobiles, petrochemistry, metallurgy, and nuclear energy and aerospace industries, in which the electromechanical devices have to operate at elevated temperatures. However, it is a long-standing challenge to simultaneously obtain high piezoelectricity and high TC. Recently, significant progress has been made on bismuth-based piezo-/ferroelectric single crystals (BPSCs) which show excellent piezoelectric performance and high TC, proving to be a promising family of novel materials for high-temperature electromechanical applications. In this highlight, we review the recent progress in BPSCs with focus on materials design, crystal growth, physical properties, crystal chemistry, and complex domain structures. In addition, the future perspectives of BPSCs are discussed.

In this work, the low-frequency noise (LFN) characteristics of hafnium-zirconium oxide (HZO) ferroelectric field-effect transistors (FeFETs) with and without high-pressure forming gas annealing (HPA) treatment are investigated. The origin of 1/f noise in the FeFET without HPA is changed from carrier number fluctuation to Hooge’s mobility fluctuation after wake-up due to the remote phonon scattering from the polarized HZO. Also, Hooge’s parameter is increased by the program/erase (P/E) cycling-induced stress. On the contrary, only the correlated mobility fluctuation is increased after the wake-up in the FeFET with HPA. Furthermore, the LFN of the FeFET with HPA shows robustness to P/E cycling-induced stress after the wake-up, showing superb endurance performance.

Lead-free Ba0.9Sr0.1Ti0.9Sn0.1O3 (BSTSn) ceramic was prepared by the sol–gel method. X-ray diffraction measurement at room temperature reveals the single-phase formation with tetragonal structure refined in the P4mm space group. Raman spectroscopy analysis at room temperature was used to confirm the structure of BSTSn ceramic sintered at 1420 °C during 5 h. The dielectric measurements were examined in the temperature range [−90 – 250 °C] and the frequency range of [100 Hz – 1 MHz]. The maximum dielectric constant was found to be ∼ 5484 (1 kHz) at room temperature. The diffuse phase transition characteristic at 1 kHz was ascribed by the modified Curie-Weiss law. Macroscopic polarization – field (P – E) hysteresis loops recorded at room temperature (RT) confirm the ferroelectric nature of BSTSn ceramic. Impedance spectroscopy analysis of BSTSn sample in the temperature range 300–380 °C reveals the presence of two relaxation contributions originated from grains and grain boundaries. Activation energies of grain and grain boundaries resistances were deduced in order to determine the conduction mechanism of the studied sample.