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Multiferroic BaTiO 3 exhibiting ferroelectric and ferromagnetic behavior was synthesized via the high-energy ball milling of pure BaTiO 3 (BTO) powders for durations ranging from 15 to 60 min, followed by pressing and sintering at 1200 °C X-ray diffraction patterns of all synthesized samples predominantly revealed a BTO phase with a tetragonal structure and a secondary Ba 12 Fe 28 Ti 15 O 84 (BFTO) phase. The BFTO phase was formed after milling for more than 30 min because of chemical interactions between the BTO powder and milling media. Vibrating sample magnetometry confirmed the ferromagnetic nature of the sintered pellets. The specific magnetization increased with increasing milling duration, reaching a maximum value of 1.15 emu/g after 60 min of milling. This increase can be attributed to the distortion of the crystal structure and presence of a secondary phase, as confirmed by scanning electron microscopy and energy-dispersive X-ray spectroscopy. Additionally, electrical characterization revealed the dielectric nature of the materials, with relative permittivity ranging from 500 to 1800, maximum spontaneous polarization from 9.77 to 11.31 μC/cm2, coercive field from 3.86 to 11.12 kV/cm, and AC conductivity from 1 × 10−6 to 1 × 10−3 S/cm. The method described in this study is a simple and cost-effective approach to produce multiferroic materials with ferroelectric and relaxor ferroelectric behavior at room temperature, broadening their potential for technological applications. [ABSTRACT FROM AUTHOR]

CeO 2 -HfO 2 solid solution thin films (Hf 1-x Ce x O 2) were deposited on Pt(111)/TiO 2 /SiO 2 /Si(100) substrates using the chemical solution deposition method. This study investigates the influence of CeO 2 content and annealing temperature on the structure and ferroelectric properties of Hf 1-x Ce x O 2 films. Ferroelectric behavior is demonstrated in polycrystalline Hf 0.80 Ce 0.20 O 2 films with thicknesses ranging from 163 to 524 nm. And the structure of the films is analyzed using glancing incidence X-ray diffraction. The comprehensive results indicate that Hf 0.80 Ce 0.20 O 2 films annealed at 850 °C exhibit excellent ferroelectricity. Square hysteresis loops associated with the ferroelectric orthorhombic phase are observed, even in the 524-nm-thick film. The remnant polarization (P r) and coercive field (E c) range from 16 to 18 μC/cm2 and 1100–1250 kV/cm, respectively, under a maximum applied electric field of 2 MV/cm for all Hf 0.80 Ce 0.20 O 2 films. Furthermore, the film presents thickness-insensitive characteristic. The current work paves the new way to design high-performance thick HfO 2 -based ferroelectric films. [ABSTRACT FROM AUTHOR]

Doped Hf 0.5 Zr 0.5 O 2 materials have drawn increasing attention due to the excellent ferroelectric properties, but the relevant research is just in the preliminary stage and the reported doped systems are rare. In this work, Ca doped Hf 0.5 Zr 0.5 O 2 (Ca:HZO) ferroelectric films were successfully fabricated via chemical solution deposition and investigated for the first time. It is observed that Ca doping induces a phase transformation from monoclinic to orthorhombic/tetragonal and then to monoclinic/tetragonal. The highest orthorhombic phase fraction is achieved in 2.5 mol% Ca doped HZO film, contributing to the optimum ferroelectric property with the largest remnant polarization of 14.00 μC/cm2 after 105 cycles. Additionally, the leakage current density is observed to decrease with increasing Ca content, which is mainly associated with the changes of grain size and surface roughness. As a result, the endurance is significantly improved in the Ca doped films, and an excellent endurance of 1010 cycles is achieved in the 2.5 mol% Ca doped film. These results suggest that Ca doping can enhance the ferroelectric and endurance properties of HZO films by optimizing the phase and morphological structure. [ABSTRACT FROM AUTHOR]

In this paper, the calcium-doped nickel-zinc nano-ferrites [Ni 0.5 Zn 0.5 Ca x Fe 2-x O 4 ; x = 0.00, 0.10, and 0.30] were prepared using the chemical co-precipitation synthesis route and studied for switching field high-frequency device applications. The structural analysis has been completed by analyzing X-ray diffraction (XRD) patterns. The Rietveld refined XRD patterns confirmed the formation of cubic spinel structure of Ca2+ substituted nickel-zinc ferrites. The detection of metal-oxygen bonds present at A and B lattice sites has been unveiled by Fourier transform infrared (FTIR) spectroscopy. The morphological studies obtained through FESEM (Field emission scanning electron microscopy) analysis showed a reduction in the particle size from 70 nm to 53 nm when the concentration of Ca2+ ions in Ni-Zn ferrites was increased. Energy dispersive spectra (EDS) confirmed the presence of elements present in the prepared composition. The structure of a cubic spinel-shaped unit cell has been verified from three active prominent Raman modes (A 1g , A 2g , and T 2g). Diffuse-reflectance spectroscopy (DRS) exhibits the increment in the bandgap values (from 1.55 eV to 1.63 eV) which helps fabricate highly efficient photovoltaic devices. The ferroelectric measurements yielded a rise in polarization values from 1.461 μC/cm2 to 18.228 μC/cm2 for 10 % Ca2+ ion substitution. The tangent loss values declined from 24 to 3 in Ni-Zn ferrites upon substituting Ca2+ ions. The Vibrating sample Magnetometer (VSM) technique found the increment in the saturation magnetization (M s) values from 34.724 emu/g to 54.662 emu/g on substituting up to 30 % Ca2+ ions in Ni-Zn ferrites. These obtained results support the material in switching field distribution for high-frequency applications. The results exhibited that the prepared samples can be applicable for switching devices, filters, and microwave absorption devices. The results revealed the maximum frequency between 12 and 18 GHz which is useful for Ku band absorption. [ABSTRACT FROM AUTHOR]

In this work, the transverse size effect of the new-generation relaxor ferroelectric Pb(In 1/2 Nb 1/2)O 3 -Pb(Mg 1/3 Nb 2/3)O 3 -PbTiO 3 (PIMNT) thin film was studied by finite element method, aiming to revealing the lateral size and shape dependence of the piezoelectric, dielectric, and pyroelectric behavior for guiding one- and two-dimensional integrated array sensor applications. The results indicated that as the aspect ratio (width to thickness ratio) decreased from 100 to 0.01, for both one-dimensional rectangular and two-dimensional square PIMNT array elements, a sharp increase in piezoelectric and dielectric constants could be observed for the PIMNT with <001> direction while a slight increase could be found for those along <111> orientation, exhibiting a strong orientation dependence. In comparison, the PIMNT with <110> direction exhibited strong shape dependence. The piezoelectric and dielectric constants of <110>-oriented square element increased more remarkably than those of the rectangular one. The pyroelectric coefficients of PIMNT exhibited weak shape dependence, decreasing from 8.5 × 10−4 C/(m2·K) to about 8.0 × 10−4 C/(m2·K) for both element shapes with transverse size decreasing. These findings give insight into the transverse size and shape effect on the new-generation PIMNT thin film and provide a guide for its design in one- and two-dimensional piezoelectric and pyroelectric array sensor applications. [ABSTRACT FROM AUTHOR]

New xYFeO 3 – (1-x) BiFeO 3 (0.0 ≤ x ≤ 1.0) multiferroic composites were prepared successfully via the chemical co-precipitation followed by high energy mechanical blending. For the structural analysis, assessment of phase purity, and characterization of oxidation states, XRD, FTIR and XPS methods were utilized, respectively. Furthermore, morphological investigations and elemental distribution within the composite samples were elucidated through FESEM and TEM imaging techniques. The VSM results indicated that the values of M s and M r increase alternately from 0.553emu/g and 0.049emu/g to 1.210emu/g and 0.166emu/g, respectively, with an increase in the YFO content from 20 % to 80 %. These values of M s do not follow a linear combination of the base phases, and the magnetization of each composite sample is accompanied by an additional value. This additional value may arise from the residual strain and interfacial magnetic and electrical interactions between the parent phases. The measurements of dielectric properties disclosed that the behavior of the samples follows the Maxwell-Wagner polarization. Moreover, the values of ε′ at the frequency of 200 Hz increased from 149 to 303 as the BFO content rose from 20 % to 80 %. In addition, the lowest recorded tanδ value was 0.56 for the 6Y4B sample at 200 Hz. Furthermore, the conductivity measurements showed that the behavior of all samples follows Johnscher's power law. • The phase-pure YFeO 3 /BiFeO 3 nanocomposites with well-dispersed particles were synthesized using the reverse co-precipitation. • The magnetostriction effect in BFO and the ferroelectric properties of YFO altered the overall magnetization in the system. • The significant enhancement of the coercive field relative to the original phases was emphasized in all composite samples. • The rise in the YFO content in the composite specimens led to a drop in the dielectric constant. [ABSTRACT FROM AUTHOR]

Ferroelectric properties of HfO 2 -based films are reported to be largely influenced by various factors including stress, grain size and oxygen vacancies. In this study, Hf 0.5 Zr 0.5 O 2 (HZO) films were deposited directly on Ti bottom electrode (Ti-BEs). The polarization switching behavior and fatigue performance exhibited notable distinctions as a result of varying oxygen vacancies in the films upon annealing under different atmosphere of N 2 , air and O 2 with different annealing time. The HZO film after being annealed in air demonstrated a comparatively larger remnant polarization (P r) value of 20.4 μC/cm2 and superior fatigue performance over 108 field cycles. Furthermore, the internal mechanisms were analyzed through density functional theory (DFT) calculations. The introduction of more oxygen vacancies was observed to reduce the formation energy of o -phase and promote the enhancement of ferroelectricity. However, it should be noted that this also resulted in an increase of leakage current. Therefore, it is crucial to carefully control the concentration of oxygen vacancies, considering the overall impact on both the reliability and ferroelectricity of thin films. The results of this work can provide an effective pathway to grow HZO ferroelectric films with high performance through the control of oxygen vacancies concentration. [ABSTRACT FROM AUTHOR]

The comparable free energy between antiferroelectric (AFE) and ferroelectric (FE) phases in NaNbO 3 (NN) leads to unstable ferroelectricity, restricting future applications for energy storage devices. In this work, lead-free NN ceramics based on different sintering aids have been rigorously synthesized and the microstructural, dielectric, and ferroelectric properties of this system have been thoroughly examined. It is found that a tiny amount of sintering aids effectively lowers the sintering temperature and manipulates the grain growth, as well as plays an essential role in the stability of FE phase in NN ceramics. The tunable ferroelectricity is observed in NN: CuO as sintering aids results in a hardening effect, whereas MnO 2 addition promotes softening behavior. More interestingly, introducing 1 wt% MnO 2 as sintering aids results in strong ferroelectricity with high polarization (P m) of 84.6 μC/cm2 stabilized by a stimulated electric field (E f) as low as 60 kV/cm. This is significantly better than other NN-based ceramics (P m is smaller than 40 μC/cm2 and E f is higher than 90 kV/cm in the NN-based systems reported earlier). Our findings demonstrate the potential of sintering aids in tailoring the ferroelectric performance of lead-free NN ceramics, offering insights into the development of environmentally friendly ferroelectric materials. [ABSTRACT FROM AUTHOR]

Flexible or wearable devices are of great interests in the modern technologies, and oxide thin films are critical components for such applications. In this work, epitaxial LiNbO 3 (LNO) thin film integrated on flexible mica substrate has been achieved. Al-doped ZnO (AZO) layer has been first deposited as buffer layer to obtain the epitaxial LNO film, furthermore AZO serves as bottom electrode for electrical measurement. The as-deposited LNO film exhibits high epitaxial quality with c-direction growth. The transmittance measurement indicates the high transparency of the film, ～85 % in visible range and ～90 % in near infrared region up to 1500 nm. The second harmonic generation (SHG) measurement confirms the nonlinearity of the flexible LNO film. The LNO/AZO/mica film also presents apparent ferroelectric response. Overall, the high-quality LNO integrated on flexible mica could be potentially applied in wearable optical and electrical devices. [ABSTRACT FROM AUTHOR]

The ever-growing need for advancement in data storage technology demands materials that can be controlled by as many degrees as possible. In this regard, multiferroic materials that show response both in electric and magnetic dimensions are of great interest especially when being investigated in two-dimensional materials that have their potential applications. In this study, we have incorporated Lanthanum (La) doped Bismuth Ferrite (BLFO), and La and Selenium (Se) co-doped BFO (BLFSO) with two-dimensional layered titanium carbide (Ti 3 C 2 T x) from the class of MXene as hybrid composites. The structural, optical and morphological investigation validated the successful etching of MXene from MAX, successful hybrid formation with conserved crystal structure and new phases of titanium dioxide (TiO 2) detected when the samples underwent heat treatment. This heat treatment was performed in order to enhance the multiferroic properties owing to the presence of TiO 2. Our results showed that the heated BLFSO-embedded Ti 3 C 2 T x hybrid composite showed maximum remnant polarization and higher dielectric response when measured with respect to the varying electric field and at different frequencies. The prepared samples also exhibited tunable polarization response at an applied static magnetic field, unveiling their magnetoelectric properties. [ABSTRACT FROM AUTHOR]

Recent studies have highlighted the ferroelectric potential of ZrO 2 thin films, which offer advantages over HfO 2 -based ferroelectric materials, such as lower thermal budget and greater natural abundance. In this research, pure ZrO 2 ferroelectric thin films were fabricated on Si substrates using chemical solution deposition with all-inorganic precursors. We explored the impacts of film thickness and HfO 2 seed layers on phase transition and ferroelectric properties. Notably, an 11 nm thick ZrO 2 film exhibited ferroelectric behavior with a remanent polarization of 12.6 μC/cm2. Due to the combined effects of tensile stress and surface energy, the increase in thickness to 30 nm led to a phase transition from the orthorhombic phase to the monoclinic phase and a resultant decrease in remanent polarization. Additionally, the introduction of a HfO 2 seed layer facilitated the crystallization of the ferroelectric o-phase, enhancing the remanent polarization to 16.5 μC/cm2 in our ∼8 nm thick ZrO 2 thin film with a ∼2 nm thick HfO 2 seed layer. These findings provide valuable insights into optimizing ferroelectric properties in ZrO 2 thin films through phase transition control. [ABSTRACT FROM AUTHOR]

This study explores the potential advantages of metal–ferroelectric–insulator–semiconductor (MFIS) structures compared with established metal–ferroelectric–semiconductor (MFS) and metal–ferroelectric–metal structures in the context of nonvolatile memory devices. Despite the superior performance of MFS structures in terms of electric field maintenance, switching speed, and power consumption, the presence of interface-related issues between the ferroelectric material and the semiconductor may degrade device performance. We propose an MFIS structure incorporating ultrathin interfacial layers (ILs) of SiO 2 , HfO 2 , and ZrO 2 to address these issues. These insulator layers enhance device endurance by reducing physical stress and trap density at the interface, thereby improving electrical performance and long-term stability. Moreover, the presence of an IL reduces charge leakage between the ferroelectric layer and semiconductor, contributing to the resolution of the sneak path current problem. An additional feature of MFIS devices is their self-rectifying behavior, simplifying circuit design and manufacturing processes by eliminating the need for an external rectification circuit, consequently reducing costs. Through a series of experiments, this study evaluates the performance of the MFIS structure, investigates the ferroelectric properties of HfAlOx-based FTJs, and examines the conduction mechanism of the MFIS structure. By comparing the o-phase of MFS, SiO 2 , HfO 2 , and ZrO 2 devices via grazing incidence X-ray diffraction (GIXRD) and using the positive-up-negative-down method to extract polarization and coercive voltage, we provide a comprehensive investigation of the impact of ultrathin ILs on ferroelectric properties. This research aims to offer valuable insights into the advancement of memory device technologies, presenting the MFIS structure as a promising platform for next-generation memory technologies. Further sections will elaborate on the experimental setup, methodology, and detailed study findings. [ABSTRACT FROM AUTHOR]

Flexoelectric effect in ferroelectric epitaxy films has attracted significant attention due to its theoretical and application potentials. However, the origin and control of flexoelectric field is not yet fully understood. In this study, we investigated the surface structure of single-domain epitaxial BiFeO 3 films with a (111) orientation using grazing incidence X-ray diffraction and X-ray reflection methods. We observed large strain gradient on the surface of the BiFeO 3 films, which produces a giant flexoelectric field up to 82.55 MV/m at the surface of 15 nm thick BiFeO 3 film. Additionally, we discovered the presence of a surface layer with lower electron density than that of the underlying BiFeO 3 layer, which is related to the flexoelectric field. Moreover, with increased film thickness, we found the strain distribution along growth direction of the film is changed, thereby leads to the decreased flexoelectric field and increasing thickness of the surface layer respectively. These findings convinced the coupling between the strain state and surface structure, changing the thickness of the ferroelectric film and consequently the strain state is an efficient way to adjust the flexoelectric field and the surface structure. [ABSTRACT FROM AUTHOR]

TiO 2 , a typical incipient ferroelectric material, has been extensively studied for its ferroelectric or dielectric properties, which can be achieved via donor and acceptor co-doping. However, the influence of doping ions on the performance of TiO 2 remains unclear. In this study, the relationship between the properties of TiO 2 and doping ions was investigated by selecting acceptors with various ionic radii. Colossal permittivity in TiO 2 was achieved by doping large-ionic-radius acceptors, forming defect complexes to pin electrons and mitigate dielectric loss. For small acceptor ionic radii, donor–acceptor co-doped TiO 2 exhibited ferroelectricity at room temperature. The electric dipole moment formed by the donor and acceptor readily rotated under an external electric field, resulting in ferroelectricity at room temperature. This study provides a design perspective for the selection of doping ions to achieve various properties in rutile-type TiO 2 ceramics. [ABSTRACT FROM AUTHOR]

Ferroelectric photovoltaic (PV) materials have garnered considerable interest because of their distinctive switchable PV characteristics. Nevertheless, their ability to function within a wide range of ambient temperatures was previously constrained. This paper describes the construction of ferroelectric capacitors featuring an Au/PZT (Pb(Zr 0. 40 Ti 0.60)O 3)/FTO (SnO 2 :F) heterojunction through the utilization of the sol-gel technique. The performance analysis findings indicate that the PZT material, following optimization of annealing temperature, displayed strong ferroelectric properties and notable frequency-dependent dielectric behavior. An increase in temperature (25°C∼300°C) revealed that short-circuit current density J sc exhibited an upward → downward → upward trend and reached 399.6 μA/cm2 at 300°C. Energy band analysis showed the presence of spontaneous polarization and a large work function difference between the bottom electrode FTO and the top electrode Au (∼0.42 eV) created a strong built-in electric field in the PZT films, which was conducive to the photogenerated carriers' separation and greatly improved the PZT film ferroelectric PV. In this paper, transparent ferroelectric materials were demonstrated for the first time to exhibit a photoelectric responsivity of up to 1.77 mA/W at a temperature of 300°C, offering a practical strategy for the implementation of transparent ferroelectric photovoltaic devices in high-temperature environments, particularly those subjected to intense solar energy harvesting and conversion. [ABSTRACT FROM AUTHOR]

Gallium nitride (GaN), one of the most popular optoelectronic materials in the semiconductor industry, has gained renewed interest as a ferroelectric material when alloyed with scandium. However, the inherent bulk photovoltaic effect (BPE) of GaN-based ferroelectrics has yet to be fully exploited. In this work, a BPE-driven self-powered photodetector based on ferroelectric Sc-doped GaN thin film was fabricated without the usage of a p - n contact. At zero bias, this device features a high responsivity of 45.9 mA/W, a high detectivity of 2.27 × 1011 Jones, a fast response speed of sub-ms-level, a high UV selectivity of 91.3, and an imaging capacity. This work demonstrates the potential of GaN-based ferroelectric thin films in energy-efficient optoelectronic devices. [ABSTRACT FROM AUTHOR]

Due to its excellent ferroelectricity and photovoltaic effect (PE), Pb 0.92 La 0.08 (Zr 0.52 Ti 0.48)O 3 (PLZT) has considerable application potential in the field of multifunctional electronic devices. In this study, an Ag/NiO/PLZT/LaNiO 3 structure is prepared on a Si substrate via a combination of sol–gel and pulsed laser deposition methods, and its ferroelectricity, PE and resistance switching (RS) properties are studied in detail. With decrease in temperature, coercive field of PLZT increases, and its residual polarization initially remains constant and then decreases. The results of ultraviolet-irradiation experiments show that the photogenerated open-circuit voltage (V o) of PLZT first increases slightly and then decreases slightly as the temperature decreases. By changing the direction of PLZT polarization, the polarization field can be oriented in the same direction or opposite to the built-in electric field formed by p – n junction at NiO/PLZT interface. Thus, the total electric field required to drive the photogenerated carriers inside the structure can be tuned, which results in different V o values. Furthermore, current–voltage characteristics of the structure are tested. It is found that as different polarization charges are generated at the NiO/PLZT interface for different PLZT polarization directions, the holes in NiO can be attracted or repelled by these polarization charges. Thereby, the interface barrier height of the p – n junction can be varied. Consequently, the structure exhibits a pronounced RS effect suitable for multilevel storage applications. These results represent an important experimental basis for the development and application of multifunctional electronic devices for optoelectronics and RS-based memories. [ABSTRACT FROM AUTHOR]

Low remnant polarization and high coercive field are the main factors limiting the practical application of Ca 3 Ti 2 O 7 -based hybrid improper ferroelectric ceramics. Based on sol-gel method and soft doping effect, (Ca 1- x Nd x) 3 Ti 2 O 7 (x= 0.003) ceramics with higher remnant polarization of ∼3.53 μC/cm2 and lower coercive field of ∼91 kV/cm were obtained. More interestingly, thanks to the large distortion amplitude of TiO 6 octahedron and effective suppression of defects such as oxygen vacancies caused by Nd3+ as a donor dopant, the remnant polarization of (Ca 1- x Nd x) 3 Ti 2 O 7 (x = 0.003 and 0.006) ceramics measured at 10 Hz using the DHM mode were as high as 7.33 μC/cm2 and 5.85 μC/cm2. These findings prove that the soft doping at A sites of Ca 3 Ti 2 O 7 material is a simple and effective strategy to enhance its hybrid improper ferroelectricity. [ABSTRACT FROM AUTHOR]

Point defects play a versatile role in modulating ferroelectricity and piezoelectricity, however, the decisive role of point-defect concentration/species in controlling macroscopic performance remains unknown. In this work, defects are implanted by reduced atmosphere annealing and/or Mn doping in Pb 0.7 Ba 0.3 ZrO 3 ceramics. i) defects induce lattice distortion, internal lattice strain and accordingly, phase structure is changed (Williamson-Hall analysis and Rietveld refinement); ii) ferroelectricity is enhanced for 0 MN and 1 MA sample with contribution of defect polarization (first-order reversal curves). iii) Joule heat is depressed as an enhanced resistivity by carrier annihilation/forming defect complex; iv) ECE behaves distinctly among 0 MN, 1 MA and 1 MH, respectively. 0 MN sample exhibits a ΔT max of 0.39 K and 1 MA possesses a ΔT max of 0.34 K. Interestingly, a broad temperature span with a low instability of ∼20 % within 288 K–423 K is obtained in 1 MH sample. This work not only provides a guideline for defects enhancing ferroelectricity and ECE, but also clarifies the reduction-resistant properties of (Pb, Ba)ZrO 3 system that are suitable for constructing base-metal multilayer ceramic capacitors in solid-state cooling devices. [ABSTRACT FROM AUTHOR]

Chromium ( C r 3 + ) doped B a T i 1 − x C r x O 3 (x = 0.0, 0.03, 0.06, and 0.09) ceramics were prepared by the solvothermal reflux approach. X-ray diffraction analysis confirmed the development of tetragonal structures with P 4 m m symmetry in the prepared samples. The SEM analysis showed that C r 3 + doping resulted in a microstructure that was dense, uniform, and had smaller grains. Surface chemical information and oxidation states were studied using X-ray photoelectron spectroscopy. The diffuse reflectance spectrum confirmed the effect of C r 3 + content on the direct optical bandgap of B a T i 1 − x C r x O 3 samples which shifts from 3.21 eV to 2.73 eV with increasing C r 3 + content. Dielectric permittivity was found to increase in the low-frequency region with increasing C r 3 + doping content up to x = 0.06, while it decreased in the high-frequency region compared to an undoped sample. The observed behavior of permittivity might be explained in terms of the formation of oxygen vacancy defects and their effects on the polarization dynamics of the material. Moreover, the addition of C r 3 + doping had a strong effect on the ferroelectric characteristics, as seen by the formation of a pinched hysteresis loop, resulting in the improvement of energy storage properties. Based on the obtained results, the sample with x = 0.06 exhibited an enhancement of about 3.3 times in energy discharge density and 26 % in storage efficiency compared to the undoped sample. This might be due to a large difference between the values of maximum and remnant polarizations, reduced tangent loss, and a smaller grain size, which makes this material attractive for use in energy storage devices. [ABSTRACT FROM AUTHOR]

In this study, the conventional solid-state sintering of lead-free (1− x)K 0.48 Na 0.52 NbO 3 - x SnO 2 piezoelectric green bodies was analysed using thermal imaging and longitudinal/transverse shrinking. The phase structure, fracture morphology, densification, permittivity, ferroelectricity, piezoelectricity, and domain-switching activation energy were investigated with increasing SnO 2 content (x). Sn4+ first occupied the A site in the ABO 3 structure and then substituted the B site with increasing x. This resulted in various contents of defect dipoles and oxygen vacancies, which were mainly responsible for the different ferroelectricity and piezoelectricity values. The permittivity and domain-switching activation energy were significantly affected by the local compositional disorder or fluctuation. Moreover, the influences of phase, densification, fine grain size, and domain wall on the electrical properties are also discussed. The optimum electrical properties, with P r = 34.7 μC/cm2, d 33 = 294 pC/N, and T C = 337 °C were determined for x = 0.30 mol%. This study provides a specific explanation and reference for the various electrical properties of lead-free piezoelectric ceramics. [ABSTRACT FROM AUTHOR]

Polycrystalline solid solutions of (1-x)PbTiO 3 -(x)Bi(Zn 0.5 Zr 0.5)O 3 [x = 0.10, 0.20, 0.30] have been synthesized by using solid state reaction method and followed by air annealing (AA)/ vacuum annealing (VA). All the samples show single phase perovskite structure with tetragonal symmetry (P4mm). Structural parameters are calculated using the Rietveld refinement technique. With the help of Scanning Electron Microscope (SEM), the surface morphology of all the samples is recorded at room temperature. The influence of VA on dielectric parameters such as dielectric constant and tangent loss of the synthesized samples are studied and compared with that of AA samples. These results unfold superior dielectric properties of VA samples as compared to AA samples. Intriguingly, the VA samples exhibit exotic ferromagnetism in non-magnetic PbTiO 3 –Bi(Zn 0.5 Zr 0.5)O 3 samples, transforming these into room temperature magneto-electric multiferroics. Besides, both the ferroelectric and ferromagnetic order parameters were found to increase with the increase in Bi(Zn 0.5 Zr 0.5)O 3 doping in PbTiO 3. The enhanced physical properties witnessed in VA PbTiO 3 –Bi(Zn 0.5 Zr 0.5)O 3 samples localized hopping of charge carriers confined to the grain. [ABSTRACT FROM AUTHOR]

BNT-6BT-based lead-free ceramics have gained significant attention due to their relatively large piezoelectric coefficients and tunable morphotropic phase boundary conditions. In this investigation, SrTiO 3 (ST) was added to BNT-6BT ceramics to fabricate the BNT-6BT- x ST (BNBT- x ST) composition. The impact of ST content on the phase structure and dielectric permittivity of the BNBT- x ST ceramics was studied. The XRD refinement data show that with increasing ST content, the crystal structure of BNBT- x ST ceramics was transformed from the morphotropic phase structure (coexisting tetragonal (P4/mmm) and pseudo-cubic (Pmm) phase) to the pseudo-cubic phase. The dielectric permittivity data of the BNBT-80ST showed that the T m (the maximum permittivity temperature) moved to −61.9 °C, which caused the room temperature to fall within the range of T m < T < T B (the Burns temperature). This makes the BNBT-80ST a superparaelectric state in relaxor ferroelectrics (RFE). Furthermore, the maximum energy density and the charge-discharge efficiency of the BNBT-80ST achieved 5.48 J/cm3 and 87% at 495 kV/cm, respectively. The energy density of the BNBT-80ST was improved by 2.97-fold and 49% compared with that of the BNBT-30ST and BNBT-70ST. This is mostly attributed to weakened ferroelectricity and improved paraelectricity in the BNBT-80ST. This investigation demonstrates that BNBT- x ST ceramics can be adjusted to a superparaelectric state with an ST content of 80%. This makes the material to possess both a large polarization and a high breakdown field. This material holds great promise for high energy density capacitor applications. [ABSTRACT FROM AUTHOR]

Improper ferroelectrics are a class of materials with the potential to design multiferroic properties. In this paper, we report on the effect of defect dipoles on the ferromagnetic and ferroelectric properties of Ca 3 Mn 2 O 7 improper ferroelectric thin films. Two kinds of defects dipoles, Mn3+-oxygen vacancy (Mn3+- V O ∙ ∙ ) and Li+-Al3+ doping, were studied. The experimental results show that both Mn3+- V O ∙ ∙ and Li+-Al3+ defect dipoles can introduce ferromagnetism in the films, and Li+-Al3+ defect dipole can also improve ferroelectricity with self-polarization. The first-principle calculations based on local density approximation demonstrate the local lattice distortion, including title MnO 6 octahedron and off-center displacement of Mn ion, plays crucial role in multiferroic properties of the film. This work gives an effective method to design the ferroelectricity and ferromagnetic properties in improper ferroelectric oxides with layered structure through constructing defect dipoles. [ABSTRACT FROM AUTHOR]

The broadband spectrum detection from ultraviolet to near-infrared is hankered in the photoelectric applications of imaging, sensing and communication. Here, a new self-powered photodetector based on ferroelectric LuMnO 3 thin film with a narrow bandgap of 1.46 eV exhibits high-sensitivity ultraviolet–visible–near infrared photodetection properties. The responsivity (R) and detectivity (D *) in sunlight are 0.4 A/W and 7.05 × 1011 Jones, which are much higher than that of other ferroelectric photodetectors. Moreover, under the monochromatic light (900 nm), the R and D * can reach 0.39 A/W and 6.89 × 1011 Jones. The outstanding photodetection performances owed to the large photocurrent output, where the short-circuit current density can reach 10.5 mA/cm2 under 1 sun illumination. The synergistic effect of ferroelectric photovoltaic effect and interface barrier effect demonstrates that the multi-driving forces can achieve high dissociation efficiency for photon-generated carriers. The excellent photodetection performances open up new application of ferroelectric materials in broadband self-powered photodetectors. [ABSTRACT FROM AUTHOR]

Ferroelectric oxide becomes the focus of memory industry again after the discovery of ferroelectricity in doped-HfO 2 polycrystalline films. Thermal stress is an important factor for the variation of ferroelectric phase content. In this paper, the effect of film stress induced by Y 2 O 3 interlayer in the ferroelectric properties of Y-doped HfO 2 (Y: HfO 2) ferroelectric films, which is deposited by chemical solution deposition (CSD), is investigated systematically by polarization-voltage measurement. Compared with Y-doped HfO 2 film without interlayer, 1 nm Y 2 O 3 interlayer enhances the remanent polarization of Y: HfO 2 film due to the effects of film stress and surface energy. And thick Y 2 O 3 interlayer benefits to reduce leakage current density. But polarization switching of HfO 2 film is restrained due to the capacitor voltage divider caused by thick Y 2 O 3 interlayer. The obvious enhance effect of Y 2 O 3 interlayer still exists in Y: HfO 2 film at high voltage due to the breakdown of Y 2 O 3 interlayer, realizing a huge remanent polarization (P r) of 22.8 μC/cm2 in Y: HfO 2 film (doping content: 4 at %). It is 3.6 times than that of ferroelectric doped-HfO 2 film without Y 2 O 3 interlayer. [ABSTRACT FROM AUTHOR]

We report on the enhancemenent of electrocaloric effect in solution cast polymer nanocomposites based on Poly(vinylidene fluoride- co -trifluoroethylene) [P(VDF-TrFE) 55-45] with Ca and Sn co-substituted BaTiO 3 ceramic fillers (Ba 0. 94 Ca 0.06 Ti 0.925 Sn 0.075 O 3 , BCST). Saturated hysteresis loops and normal ferroelectric behaviour of the copolymer-based nanocomposites -as opposed to the relaxor ferroelectric nature of the terpolymer-based ones-allow the utilization of the indirect method to estimate the electrocaloric properties. Both the dielectric constant and electrocaloric temperature change (ΔT) increases as the particle content increases. Maximum adiabatic temperature change was obtained as 6.96 K under 900 kV/cm for the 10 vol % BCST containing polymer composite around the Curie temperature of the copolymer (70 °C). This relatively large electrocaloric strength is slightly lower than those obtained for terpolymer-based nanocomposites. [ABSTRACT FROM AUTHOR]

This study sheds a light on the in-situ growth of nanoflakes structure in Bi 0. 9 La 0. 1 Fe 0. 5 Mn 0. 5 O 3 (BLFMO) thin film. The BLFMO thin films of various thicknesses were grown on LaNiO 3 (LNO) coated Si (100) substrates using pulsed laser deposition technique. A long-range crystal structure of the as prepared BLFMO thin films was studied by X-ray diffraction measurements, which shows that the LNO buffer layer allows growth for a specific orientation. The compact and densely packed nanoflake structures in BLFMO thin film samples were confirmed by surface morphological investigations. To measure the polarization versus electric field (p - E) loop of BLFMO chip samples, a standard bipolar sinusoidal waveform with its magnitude of 250 kV/cm was applied at the frequency of 1 kHz. The maximum saturation and remnant polarizations of 104.50 μC/cm2 and 86.24 μC/cm2 respectively were probed for a critical thickness (420 nm) of the BLFMO layer. The voltage polarity-dependent leakage current behavior of Ag/BLFMO/LNO thin-film capacitor is thoroughly explored in detail. The value of leakage current density was observed from 1.16 × 10−4 to 2.24 × 10−5 J/cm2 for BLFMO thin films at an external applied electric field of 300 kV/cm. The highest tunability ∼60.20% and minimum temperature capacitance coefficient ∼1.23 × 10−3 were also observed for the same critical thickness of proposed chip element. The present study may open up a new opportunity to fabricate thin film based ferroelectric memory devices. [Display omitted] [ABSTRACT FROM AUTHOR]

With its complicated composition architecture, (Bi 0.5 Na 0.5)TiO 3 (BNT)-based relaxor ferroelectrics exhibit distinctive dielectric relaxation phenomena and attractive characteristics. The structural, dielectric, and ferroelectric characteristics of (1– x)(Bi 0.5 Na 0.4 K 0.1)TiO 3 - x (Ba 0.5 Sr 0.5)TiO 3 (BNKT- x BST) solid solutions with x = 0–0.4 were thoroughly examined in this study. The x = 0.1 and 0.2 versions exhibited unexpected ferroelectricity enhancement, and the depolarization temperatures and ferroelectric-relaxor transition temperature were both increased compared to that of the BNKT undoped sample. This enhancement is due to the creation of a tetragonal ferroelectric phase after the introduction of a moderate BST member, according to room temperature and temperature-dependent x-ray diffraction data. The characterization of ferroelectric properties indicated that ferroelectricity was enhanced by increasing the rapidly declining temperatures for the remnant polarization and coercive field, compared to those of the BNKT undoped sample. This discovery contributes to a better understanding of the relationship between the structure and properties of complex relaxor ferroelectrics. A phase diagram of the BNKT- x BST solid solution is also provided, which can be used to guide the search for specific lead-free functional materials for the capacitors, actuators, and transducers based on this eco-friendly system. [ABSTRACT FROM AUTHOR]

Tuning single-crystalline transition metal oxide to possess multi functionalities, for instance, ferroelectricity and ferromagnetism through strain and defect engineering is crucial for facilitating related functionalities that have implications for device applications. To clarify the dependence relationship between strain and defect for emergent ferroics in complex oxide, in this study, we report the ferroelectric and magnetic properties of oxygen-deficient SrTiO 3-σ (STO 3-σ) thin films in rigid heterostructure and freestanding forms. By an appropriate introduction of oxygen vacancies, the STO 3-σ exhibits the coexistence of ferroelectricity and ferromagnetism in its rigid heterostructure, however, these features are eliminated if STO 3-σ turns to the freestanding thin films via a water-dissolution of Sr 3 Al 2 O 6 (SAO) sacrifice interlayer. Our experimental findings demonstrate that both ferroelectricity and ferromagnetism of STO 3-σ need the stabilization of the defects by strain which enlarges the activation energy of the anionic defect suggesting a promising multiferroic engineering method. Meanwhile, our study also provides valuable information on flexoelectric/flex magnet devices. [Display omitted] [ABSTRACT FROM AUTHOR]

Ca 3 (Ti 1- x Co x) 2 O 7 ceramics were prepared by a tartaric acid sol-gel method and sintered in an oxygen atmosphere. The introduction of Co2+/Co3+ as acceptor dopants leads to the formation of more oxygen vacancies and defect dipoles in Ca 3 (Ti 1- x Co x) 2 O 7 ceramics. Oxygen vacancy and defect dipoles lead to the transition of dielectric, leakage, and ferroelectric behaviors of Ca 3 (Ti 1- x Co x) 2 O 7 ceramics. The coexistence of hybrid improper ferroelectricity and ferromagnetism at room temperature in Ca 3 (Ti 1- x Co x) 2 O 7 ceramics has been successfully realized through the superexchange interaction of Co–O–Co. Ca 3 (Ti 1- x Co x) 2 O 7 ceramics exhibit superior ferroelectricity (the remnant polarization is 3.29 μC/cm2) and enhanced ferromagnetism (the remnant magnetization reaches 6.4×10−3 emu/g). This strategy based on the introduction of transition metal ions with unfilled 3d shells at B sites is an important approach to realize novel room-temperature single-phase multiferroic materials for Ca 3 Ti 2 O 7 -based materials. [ABSTRACT FROM AUTHOR]

In the current study, pristine and a series of La and Co-doped dysprosium chromite (Dy 1-y La y Cr 1-x Co x O 3) nanoparticles have been fabricated via a facile microemulsion technique. The influence of doping was evaluated based on structural, ferroelectric, dielectric, and photocatalytic properties. The prepared nanoparticles were characterized by XRD, SEM, Raman, and UV–Vis techniques. XRD patterns confirm the synthesis of a monophase orthorhombic structure with space group Pbnm with an average crystalline size in the 18–37 nm range. The saturation polarization (Ps), remanence (Pr), and coercivity (Hc) were determined using a hysteresis loop, and it was observed that by increasing the concentration of dopants, the value of Ps and Pr were improved. According to the PL spectra, highly substituted materials had a low recombination rate and higher charge separation (e− - h+), which was ultimately accountable for higher photocatalytic activity. The dielectric loss decreases with frequency and dopant concentration. The photocatalytic activity of Dy 1-y La y Cr 1-x Co x O 3 was investigated against Crystal Violet (CV) dye under sunlight irradiation. The Dy 1-y La y Cr 1-x Co x O 3 furnished a 70% dye degradation in 90 min, which is attributed to the tunned bandgap and efficient electron-hole pair separation and the photocatalytic activity under visible light making Dy 1-y La y Cr 1-x Co x O 3 a promising photocatalyst for dye removal from wastewater. [ABSTRACT FROM AUTHOR]

To analyze the effect of PFN content on the microstructure and electrical properties of x Pb(Fe 0.5 Nb 0.5)O 3 –(0.57− x)Pb(Ni 1/3 Nb 2/3)O 3 –0.43Pb(Zr 0.3 Ti 0.7)O 3 , the doping of x PFN–PNN–PZT) were systematically studied with 0.015 ≤ x ≤ 0.075. XRD patterns and Raman spectra analysis reveal that PFN diffuses into PNN–PZT perovskite lattice and forms new quaternary solid solution. With the increase of PFN content x , the proportion of rhombohedral (R) phase decreases gradually, whereas the proportion of tetragonal (T) phase displays a contrary trend. In particular, R – T coexistence near MPB was observed at x = 0.045. Meanwhile, optimized electrical properties of d 33 = 961 pC/N, k p = 0.716, ε r = 6298, and tan δ = 3.1% are achieved for the 0.045PFN–PNN–PZT ceramics. Moreover, the ceramics at MPB showed larger remnant polarization P r = 24.55 μC/cm2, smaller coercive field E c = 0.36 kV/mm, and lower dielectric relaxor degree γ = 1.813. All these results reveal that the enhanced electrical properties could be attributed to synergistic phase boundary motion, dielectric relaxor behavior and ferroelectric hysteresis effect. [ABSTRACT FROM AUTHOR]

The main reason ZnO is attractive for optoelectronic applications is its polarization behavior, which can modify its optical and electronic properties. Here, the polarization of ZnO is highly dependent on its structure and morphology. We study the polarization behavior of ZnO with different structures and morphology. A seedless ZnO nanocolumnars (ZnO NCs) array is fabricated using DC-unbalanced magnetron sputtering (DC-UBMS) with further thermal annealing treatment. Thermal annealing transforms the cone-like ZnO NCs to become rod-like ZnO NCs and significantly reduces the intensity of the crystal plane (002). Thermal annealing changes the polarization, where the annealed-ZnO 600°C exhibits the highest polarization that promotes the increase in lattice constant c and crystallite size. We found a football-like polarization response without saturation polarization, which indicates a presence of leakage current and defect on the samples. Interestingly, a ferroelectric characteristic is observed in annealed-ZnO 800°C with lower polarization than the annealed-ZnO 600°C. The origin of ferroelectricity is further investigated using a comprehensive study. This study provides a new understanding of polarization behavior on ZnO NCs, which is the essential key in designing switchable and non-volatile-based devices. [ABSTRACT FROM AUTHOR]

Hf 1-x Zr x O 2 (HZO) thin films are one of the most attractive HfO 2 -based ferroelectric thin films, with potential applications in next-generation ferroelectric devices. Since HZO thin films can have various phases depending on the process conditions and composition, many studies have investigated the change of ferroelectricity according to the process conditions. In this study, we investigate the effect of the Zr content on the ferroelectricity of as-grown crystalline HZO thin films using thermally stable cyclopentadienyl-based precursors via atomic layer deposition. While most of the previously reported HZO thin films require a post-thermal process for crystallization, the transition behavior of paraelectric, ferroelectric, and antiferroelectric characters was clearly observed for the first time without post-annealing. Moreover, based on the boundary composition of the Zr-rich HZO thin film, the ferroelectricity can be changed to an antiferroelectric character by the post-thermal process. Finally, process conditions for securing stable endurance characteristics of ferroelectric and antiferroelectric properties were presented. Therefore, these results suggest a process strategy suitable for various device applications based on the ferroelectricity and antiferroelectricity of HZO thin films with low thermal budget. [Display omitted] • The Hf 1-x Zr x O 2 of various compositions deposited by ALD using Cp-based precursors. • As-deposited Hf 1-x Zr x O 2 exhibited stable crystallization. • As-deposited Hf 1-x Zr x O 2 exhibited ferroelectric transition behavior. • Ferroelectric transition behavior of as-deposited Hf 1-x Zr x O 2 changed by annealing. • Process conditions for securing stable endurance characteristics were presented. [ABSTRACT FROM AUTHOR]

A 4 B 2 O 9 (A = Co, Fe, Mn, Ni, B = Nb, Ta) compounds with a corundum-type structure can host multiferroic phenomena and present magnetoelectric coupling to achieve manipulations of their ground states by external fields. High quality Ni-doped Co 4 Nb 2 O 9 single crystals of Co 3 NiNb 2 O 9 have been synthesized for the first time using optical floating zone technique. Co 3 NiNb 2 O 9 exhibits an antiferromagnetic order at 32 K with an easy magnetization axis in the ab plane. Field-dependent magnetizations at 20 K along [100] and [120] directions have a slope change at 6 and 9 kOe, respectively, indicating a spin-flop transition or spin rotation in the ab plane. Temperature dependence of dielectric constants along [100] and [120] directions show a magnetic-field-induced peak near the antiferromagnetic transition, proving a sizable magnetodielectric effect. Pyroelectric currents along [100] and [120] directions also have a divergent behavior near the transition under magnetic fields, manifesting a magnetoelectric coupling effect. The electric polarization along [120] direction reaches 128 μ C / m 2 under a magnetic field of 40 kOe, larger than that in most phases of the A 4 B 2 O 9 system. [ABSTRACT FROM AUTHOR]

A complete understanding of magnetoelectric (ME) coupling in polar magnet Fe 2 Mo 3 O 8 (FMO) remains elusive. Here, we report the magnetodielectric (MD) and ME effects of (Fe 1- x Zn x) 2 Mo 3 O 8 (x = 0, 0.05) single crystals. The observation of MD effect in FMO shows a sharp peak once T is below T N due to the metamagnetic transition, which is converted into an obvious step upon cooling. Meanwhile, the change of magnetization M modulated by electric field E is striking at the dielectric constant peak/step. In (Fe 0.95 Zn 0.05) 2 Mo 3 O 8 , however, the sharp peak at just below T N is intact, while the step at much lower T N is highly damaged. The ME response to 5% Zn2+ dopants at the two T -ranges shows different behavior. Combining with spin wave theory, it is possible to speculate that the inverse Dzyaloshinskii-Moriya interaction might play a dominant role in the ME nature at just below T N , which is different from that at much lower T N. [ABSTRACT FROM AUTHOR]

In this study, Tm-doped 0.7Bi 1− x Tm x FeO 3 –0.3BaTiO 3 (x = 0–0.05) ceramics have been fabricated using traditional solid-phase reactions and their structural, morphological, and dielectric as well as multiferroic properties are investigated. X-ray diffraction and Rietveld refinement indicated the formation of a Tm-modulated morphotropic phase boundary (MPB) from the rhombohedral (R 3c) and tetragonal (P 4mm) phases to a single P 4mm phase for Tm content of x = 0.02–0.03. Tm occupation of lattice sites is strongly suggested at both the A and B sites in the ABO 3 -type perovskite structure, which is supported by the obtained Raman spectra, the calculated tolerance factor, and dielectric relaxation characteristics. With the Tm-induced aforementioned–structural modification, the dielectric constant, remnant polarization (P r), and remnant magnetization (M r) values indicate that the dielectric and multiferroic properties are greatly improved. The obtained maximum remnant polarization (2 P r = 35.28 μC/cm2) and remnant magnetization (2 M r = 0.56 emu/g) are approximately two and seven times larger, respectively, than those of the sample without Tm substitution (x = 0). With increasing the Tm content, the remnant polarization, and the remnant magnetization exhibit almost the same trends in variation, indicating the possible existence of a relatively strong magnetoelectric coupling effect. Our study may provide a substitution strategy (structural modification by substituting the same element into two different lattice sites) to efficiently enhance the dielectric and multiferroic properties of BiFeO 3 –BaTiO 3 -based ceramics. [ABSTRACT FROM AUTHOR]

The built-in electric field existing in heterojunction of hybrid photocatalyst is favorable to separate the photogenerated carriers in photocatalytic reaction. Besides, the electric field existing in the whole ferroelectric bulk can also effectively separate the photogenerated carriers. Here the catalytic reaction is enhanced through the enlarged electric field contributed by both p-n junction and the ferroelectric polarization. A new composite is prepared with the n-type single-crystal PbTiO 3 nanoplate coated with the p-type NiO particles, and its photocatalytic degradation rate of RhB (0.253 min−1) is 4.71 times of pure PbTiO 3 (0.0537 min−1) due to the contribution of p-n junction. In addition, the piezo-phototronic effect is applied to further enhance the photocatalytic performance. Under light and ultrasonic excitation, the screening effect of ferroelectric polarization can be broken by the alternating piezoelectric potential due to the periodic mechanical stress, and thus the reaction rate of piezo-photocatalytic degradation of RhB (0.461 min−1) is 1.82 times of photocatalytic reaction rate (0.253 min−1) for NiO@PbTiO 3 composite and 3.34 times of the piezo-photocatalytic reaction rate for pure PbTiO 3 (0.138 min−1). This work is helpful to clarify the piezo-photocatalytic mechanism and develop efficient photocatalysts. [ABSTRACT FROM AUTHOR]

Although the nonstoichiometric influence on the small-signal dielectric and piezoelectric properties of (Bi 0.5 Na 0.5)TiO 3 (BNT)-based ferroelectrics has been studied extensively over the past decade, the features of large-signal electric field-induced strain (electrostrain), which are of particular importance to actuator devices, have not been thoroughly investigated. In this study, we used the solid-state reaction method to manufacture nonstoichiometric 0.94(Bi 0.5+ x Na 0.5− x)TiO 3 -0.06BT (BNT x -6BT) ceramics, where x = 0.0–0.05, and investigated the nonstoichiometric effect on the dielectric and large-signal electromechanical properties, with special emphasis on the electrostrain properties. Our results suggest that the room-temperature phase structures of BNT x -6BT ceramics changed from a regular ferroelectric phase to a relaxor ferroelectric phase as the Bi/Na ratio increased from stoichiometric 50/50 to nonstoichiometric 55/45 owing to the nonstoichiometric effect on the long-range ferroelectric order. In the x = 0.02 nonstoichiometric composition, an ultrahigh and electrostrictive-type electrostrain of 0.53% was identified. Compared to their stoichiometric counterparts, nonstoichiometric compositions have stronger temperature stability during polarization, resulting in good temperature stability of the electrostrain. Our findings not only reveal the nonstoichiometric effect on the phase evolution and its impact on the dielectric and large-signal electromechanical properties of BNT x -6BT ceramics but also provide a new method for tailoring the large-signal electrostrain properties of BNT-based ceramics. [ABSTRACT FROM AUTHOR]

Ferroelectric field-effect transistors (FeFETs) hold great promises for application in modern semiconducting industry as memory or logic devices. Intensive studies have been done on improving the performance of FeFET, which mostly rely on the electrical polarization properties of ferroelectric gate. However, the influence of the piezoelectric effect of ferroelectric gate on the semiconducting channel has not been explored to a large extent. In this work, we use gate voltage-dependent photoluminescence (PL) spectroscopy to study the piezoelectric effect of P(VDF-TrFE) gate on monolayer WSe 2 channel in FeFETs. The PL peak of monolayer WSe 2 undergoes a blue shift or red shift when gate voltage is applied through the ferroelectric layer, while no peak shift is observed when gate voltage is applied through the SiO 2 layer. Raman spectroscopy measurements confirm the presence of in-plane strain in monolayer WSe 2. Qualitative theoretical analysis and discussion suggest that the piezoelectricity of monolayer WSe 2 and the P(VDF-TrFE) deformation caused by inverse piezoelectric effect are the main factors that cause strain in monolayer WSe 2. These results demonstrate that the band structure of two-dimensional channel, especially monolayer two-dimensional materials, can be modulated in FeFETs, which should not be neglected under large gate voltage in FeFETs. [ABSTRACT FROM AUTHOR]

In this report, the local structure geometry of BaTi 1-x Ni x O 3 (0.0 ≤ x ≤ 0.06) ceramics has been studied through synchrotron based x-ray-absorption spectroscopy, measured at the Ti K, Ba L 3 and Ni K-edges at room temperature. The x-ray absorption near edge spectroscopy (XANES) at Ti K-edge confirms the TiO 6 octahedron geometry of Ti atom due hybridization between Ti(3d)-O(2p) orbitals and signifies the non-centrosymmetric nature of BaTiO 3 samples. However, Ti–O off-center displacement (non-centrosymmetric) is disturbed under the effect of Ni doping as a result of oxygen vacancies formation. More interestingly, XANES studies at Ni K-edge ensure successful substitution of Ni in BaTiO 3 as Ni2+ ions. Extended x-ray absorption fine structure (EXAFS) data at Ni K-edge have been fitted to estimate pertinent local structural parameters of the Ni–O, Ni–Ba, Ni–Ti and Ni–Ni shells (viz. bond lengths and disorder parameters) and it also reveal that the structural disorders around the Ti sites in the doped BaTiO 3 expand with Ni doping. The mixed-valence states of titanium ion, i.e., Ti4+ and Ti3+ in the doped samples were established with the x-ray photoelectron spectroscopy (XPS). Moreover, XPS divulges the creation of oxygen vacancies due to Ni doping in BaTiO 3 matrix. The complementary information about the lattice vibration is analyzed through Raman studies that approve the softening of the transverse optical (TO) mode present at 515 cm−1. The temperature dependent ferroelectric studies affirm that the ferroelectricity vanishes in the doped samples due to the decrement in the off-center displacement between the Ti4+ and O2− ions in the TiO 6 octahedral geometry. Differential thermal analysis (DTA) exhibits a ferroelectric tetragonal to para-electric cubic phase transition in the pristine as well as Ni doped BaTiO 3 samples. [ABSTRACT FROM AUTHOR]

Ba (1- x) (Na 0.5 Ce 0.5) x Bi 8 Ti 7 O 27 (BBIT: x (NC)) intergrowth bismuth layer-structured piezoelectric ceramics with enhanced piezoelectric and ferroelectric properties were synthesized by the traditional solid-state reaction process. Our systematic investigations show that the BBIT: x (NC) ceramics have a single intergrowth structure with an orthogonal phase. The reason of the internal bias field in BBIT: x (NC) ceramics was analyzed by atmosphere sintering, which was related to the defects of Na/Ce doped BBIT ceramics. Moreover, the electrical properties of Na/Ce co-doped BBIT ceramics were significantly improved. The sample with doping content x = 0.3 exhibits the most excellent piezoelectric constant d 33 of 21.8 pC/N and a high Curie temperature T c of 541 °C, which may be attributed to the enhancement of ferroelectric polarization and lattice mismatch, respectively. In addition, the remnant polarization (2 P r) was improved from 16.8 μC/cm2 to 20.2 μC/cm2, and the d 33 was 20.6 pC/N after annealing at 450 °C, indicating that the ceramic samples had good thermal stability. Our results suggest that BBIT: 0.3(NC) ceramics may be a promising candidate for high-temperature piezoelectric applications. [ABSTRACT FROM AUTHOR]

High-entropy perovskite oxides with ferroelectricity have not been reported so far because these oxides have highly symmetric cubic structures. In this study, we propose a strategy of introducing morphotropic phase boundaries to obtain ferroelectricity in high-entropy perovskite oxides. We demonstrate the feasibility of the concept using (1−x)Pb(Mg 0.2 Zn 0.2 Nb 0.2 Ta 0.2 W 0.2)O 3 –xPbTiO 3 as a model system. It is anticipated that this concept can be applied to design and prepare various high-entropy ferroelectric and piezoelectric perovskite oxides. [ABSTRACT FROM AUTHOR]

0.3Pb(Mg 1/3 Nb 2/3)O 3 -0.7Pb(Zr 0.52 Ti 0.48)O 3 /Pb(Zr 0.52 Ti 0.48)O 3 (PMN-PZT/PZT) piezoelectric films have been deposited on Pt/Ti/SiO 2 /Si substrates via in-situ magnetron sputtering process. The purpose of this work was to investigate heterogeneous interfaces-dependent preferential orientation, micro-morphology, and piezoelectric behaviors of the PMN-PZT/PZT films. Uniform and dense columnar grains are observed by Scanning electron microscope (SEM) analysis as increasing the number of hetero-interfaces. For the film with five heterogeneous interfaces (H5), the superior ferroelectricity (2P r = 21.6 μC/cm2, 2 E c = 60 kV/cm) and dielectricity (ε r = 1012.1, tan δ = 0.022 at 1 kHz) are obtained, which arises from highly dense columnar grain and the influence of heterogeneous interface strain. Moreover, an excellent piezoelectric constant e 31 of 8.2C/m2 is achieved in H5 film, which is 3.5 times larger than that of PZT film. It is expected that this study will simulates the design and synthesis of new functional materials, and provides a guidance for actuators device fabrication and applications. [ABSTRACT FROM AUTHOR]

The green-phase compound Sm 2 BaCuO 5 has recently drawn significant attention due to the prominent linear magnetoelectric (ME) coupling effect. Herein, we report a successful chemical doping control of magnetic order and ME effect in Lu3+-doped multiferroic Sm 2 BaCuO 5. Upon a small amount of Lu3+ doping, it is suggested that the majority of Cu ions interact through Sm3+ and order at T N1 ∼ 23 K, whereas some Cu2+ interacting through Lu3+ can lead to another transition at T * ∼21 K–16 K upon doping Lu3+ ions from 5% to 20%. More interestingly, this emergent magnetic order is concomitant with a broad valley in the pyroelectric current and dielectric anomaly, providing clear evidence of intrinsic coupling between magnetic and ferroelectric orders. In contrast to the parent phase, significant enhancement of the linear ME coefficient is obtained. Our results unveil the importance of interplay of 4 f -3 d magnetic interactions in inducing ferroelectricity and offer an alternative route to achieve high performance in ME coupling. [ABSTRACT FROM AUTHOR]

(K,Na)NbO 3 (KNN)-based ceramics have been proven to be formidable candidates among lead-free piezoelectric materials, yet poor reproducibility always hinders their progress. In the present study, the effects of low lithium substitution on the electrical properties and microstructure of (K 0.5 Na 0.5) 1- x Li x NbO 3 (KNLN) ceramics were investigated. All samples were synthesized by the sol-gel method. The Curie temperature (T C) of the ceramics shifted to higher temperature and gradually decreased the monoclinic-tetragonal (T M-T) phase transition. Li+ substitution had a prominent effect on the ferroelectric properties and improved the piezoelectric coefficient (d 33) up to 181 pC/N. X-Ray Diffraction (XRD) studies and Field Emission Scanning Electron Microscopy (FESEM) images revealed an inevitable tetragonal tungsten bronze (TTB) secondary phase, which was formed during the preparation process. It was demonstrated that the volatilization of Li+ cations facilitated TTB growth. The coexistence of two different phase structures proved to enhance the KNN piezoelectric performance. • Higher Li substitution promotes a tetragonal tungsten bronze phase in KNLN ceramics. • Reduced PPT and greater domain wall stabilities are achieved simultaneously. • A high d 33 value (∼181 pC/N) is obtained by coexisting monoclinic and tetragonal phases. • Poling at one half of the T C plays an important role in the enhancement. [ABSTRACT FROM AUTHOR]

High quality BiFeO 3 film with enhanced remanent polarization and magnetization attracts much interest for its great application potential in information storage and photoelectric devices. Here we grew single-crystal epitaxial BiFeO 3 film on SrTiO 3 substrate through hydrothermal method at low temperature, the film has a quality higher than any reported BiFeO 3 films grown through hydrothermal method. Furthermore, BiFeO 3 film was grown through a 25 min rapid microwave-assisted hydrothermal process. The two BiFeO 3 films exhibited obvious light response to periodically switching on and off of a LED light, and the film grown through microwave-assisted hydrothermal method produced a 4.7V open-circuit voltage exceeding the band gap of BiFeO 3 originating from the ferroelectric photovoltaic effect. These results demonstrate that hydrothermal and microwave-assisted hydrothermal method are simple, inexpensive and rapid to grow high quality epitaxial BiFeO 3 film with potential application in photoelectric detection and photovoltaic. [ABSTRACT FROM AUTHOR]