Among the lead-free piezoceramics, (1−x)BiFeO3−xBaTiO3 (BF-BT) is considered a promising candidate for high-temperature piezoelectric materials owing to its high Curie temperature (TC>400∘C) and good electromechanical properties. In this work, the hydrothermal synthesis method was used to prepare the precursor powders of BiFeO3 and BaTiO3, and then the mixed powder compacts with the chemical composition of 0.7BF–0.3BT were sintered under pressureless conditions. The influence of the hydrothermal reaction times (12–24h) of BiFeO3 on the structures and electric properties of the sintered ceramics was instigated. First, all the samples synthesized with the tetragonal BaTiO3 and BiFeO3 powders were identified with relatively stable dielectric properties. As the hydrothermal reaction time to synthesize BiFeO3 increased, the dielectric properties as well as the temperature stability of the 0.7BiFeO3–0.3BaTiO3 ceramics also improved. At the condition of a hydrothermal reaction time of 24h, the sample obtained possesses both the lowest temperature coefficient of dielectric constant (Tkε=1.53×10−2/∘C between RT and 300∘C) and the highest Curie temperature (TC=471∘C at 100kHz). Moreover, at high temperatures, it exhibits a higher AC impedance than others. The calculating result based on the resistive constant-phase-element model (R-CPE) circuit model showed that the grain boundary of the 0.7BF–0.3BT ceramics contributes more resistance to the conductivity at high temperatures. In summary, the hydrothermal reaction proved to be a useful way that achieves the preparation of single-phase 0.7BF–0.3BT ceramics with improved electrical properties.

Two-dimensional α-In2Se3 exhibits simultaneous intercorrelated in-plane and out-of-plane polarization, making it a highly promising material for use in memories, synapses, sensors, detectors, and optoelectronic devices. With its narrow bandgap, α-In2Se3 is particularly attractive for applications in photodetection. However, relatively little research has been conducted on the out-of-plane photoconductive and bulk photovoltaic effects in α-In2Se3. This limits the potential of α-In2Se3 in the device innovation and performance modification. Herein, we have developed an α-In2Se3-based heterojunction with a transparent electrode of two-dimensional Ta2NiS5. The out-of-plane electric field can effectively separate the photo-generated electron–hole pairs in the heterojunction, resulting in an out-of-plane responsivity (R), external quantum efficiency (EQE), and specific detectivity (D*) of 0.78mA/W, 10−3% and 1.14×108 Jones, respectively. The out-of-plane bulk photovoltaic effect has been demonstrated by changes in the short circuit current (SCC) and open circuit voltage (Voc) with different optical power intensity and temperature, which indicates that α-In2Se3-based heterojunctions has application potential in mid-far infrared light detection based on its out-of-plane photoconductive and bulk photovoltaic effects. Although the out-of-plane photoconductive and bulk photovoltaic effects are relatively lower than that of traditional materials, the findings pave the way for a better understanding of the out-of-plane characteristics of two-dimensional α-In2Se3 and related heterojunctions. Furthermore, the results highlight the application potential of α-In2Se3 in low-power device innovation and performance modification.

High-density ferroelectric BiFeO3 (BFO) nanodot arrays were developed through template-assisted tailoring of epitaxial thin films. By combining piezoresponse force microscopy (PFM) and Kelvin probe force microscopy (KPFM) imaging techniques, we found that oxygen vacancies in nanodot arrays can be transported in the presence of an electric field. Besides triple-center domains, quadruple-center domains with different vertical polarizations were also identified. This was confirmed by combining the measurements of the domain switching and polarization vector distribution. The competition between the accumulation of mobile charges, such as oxygen vacancies, on the interface and the geometric constraints of nanodots led to the formation of these topological domain states. These abnormal multi-center topological defect states pave the way for improving the storage density of ferroelectric memory devices.

Ferroelectric nanocapacitors have attracted intensive research interest due to their novel functionalities and potential application in nanodevices. However, due to the lack of knowledge of domain evolution in isolated nanocapacitors, precise manipulation of topological domain switching in the nanocapacitor is still a challenge. Here, we report unique bubble and cylindrical domains in the well-ordered BiFeO3 nanocapacitor array. The transformation of bubble, cylindrical and mono domains in isolated ferroelectric nanocapacitor has been demonstrated via scanning probe microscopy (SPM). The bubble domain can be erased to mono domain or written to cylindrical domain and mono domain by positive and negative voltage, respectively. Additionally, the domain evolution rules, which are mainly affected by the depolarization field, have been observed in the nanocapacitors with different domain structures. This work will be helpful in understanding the domain evolution in ferroelectric nanocapacitors and providing guidance on the manipulation of nanoscale topological domains.

Monolayer molybdenum disulfide (MoS2) has weak light absorption due to its atomically-thin thickness, thus hindering the development of MoS2-based optoelectronic devices. CdSxSe1−x has excellent photoelectric performance in the visible light range, and its nanostructure shows great potential in new nanoscale electronic and optoelectronic devices. In this work, a composite photodetector device with the combination of monolayer MoS2 nanosheets and CdS0.42Se0.58 nanobelts has been successfully prepared, which can not only maintain the inherent excellent properties of the two blocks, but also play a synergistic role between them, thus improving the photoelectric performance of the device. The monolayer MoS2 nanosheet /CdS0.42Se0.58 nanobelt photodetector has a wide spectral response range (400–800nm), high responsivity (527.22A/W) and large external quantum efficiency (EQE) (1.06×105%). Compared with the isolated monolayer MoS2 nanosheet, both the responsivity and EQE of the hybrid photodetector are increased by 117.4 times under 620nm illumination. This study provides a way to prepare hybrid photodetectors with wide spectral response and high responsivity.

BiFeO3–BaTiO3 is a promising lead-free piezoelectric ceramic, exhibiting high Curie temperature and superior electrochemical characteristics. In this work, (1−x)BiFeO3–xBaTiO3 (BF–xBT, x=0.26, 0.28, 0.30, 0.32, 0.34, 0.36) ceramics were fabricated using the conventional solid-state reaction method through precise composition control. Multiple characterization techniques, including X-ray powder diffraction (XRD), scanning electron microscope (SEM), and electrical property testing systems, were applied to systematically examine the crystallographic structure, microstructure, as well as the dielectric, ferroelectric and piezoelectric properties of the BF–xBT ceramics. The XRD results confirm that all compositions exhibit a typical perovskite structure, transitioning from a single rhombohedral phase to a rhombohedral–cubic phase mixture as the BT content increases. SEM shows apparent core–shell microstructures in the ceramics. Notably, the results demonstrated that the BF–0.30BT ceramic exhibits the maximum piezoelectric constant (d33) ∼217pC/N, while the BF–0.34BT ceramic displays the maximum converse piezoelectric constant (d33∗)∼323pm/V, which highlights the suitability of BF–BT ceramics for high-performance piezoelectric applications.

(Pb0.8Ba0.2)[(Zn1/3Nb2/3)0.7Ti0.3]O3 relaxor-type ferroelectric ceramics was obtained via classical solid-state reaction. The hysteresis loop results were discussed in the frame of ergodicity criterium around the characteristic ferroelectric relaxor freezing temperature. Slimer hysteresis loops were observed below the freezing temperature reflecting an ergodic relaxor behavior. Above this temperature, estimated around 223K for the studied system, larger and unsaturated like ferroelectric hysteresis loops were observed. This temperature also coincides with the slope change on maximum polarization and inflection point of remnant polarization curves. Energy storage, energy loss and efficiency values were determined in a wide temperature range. While the recoverable energy density shows relatively low values (0.23J/cm3), there are interesting behaviors for this parameter and for the efficiency, since the two physical quantities increase versus temperature and the efficiency even reaches the value of 97%.

The paper presents the results of an experimental study of the local polarization reversal and creation of domains by a biased tip of scanning probe microscope (SPM) in lithium niobate single crystals of congruent composition with a surface layer modified by soft proton exchange (SPE). The depth dependence of H+ ions concentration in the SPE-modified layer measured by confocal Raman microscopy demonstrates a sufficient composition gradient. The creation of isolated domains and stripe domain structures has been done by two switching modes: (1) point switching by field application in separated points and (2) line scanning switching by motion of the biased tip being in contact with the sample surface. For point switching for pulse durations less than 10s, the logarithmic dependence of the domain diameter on the pulse duration was observed. The change of the dependence to a linear one for pulse duration above 10s has been attributed to the transition from the stochastic step generation at the domain wall to the deterministic one at the domain vertexes. The periodical structure of stripe domains was created in SPE CLN planar waveguides by scanning at elevated temperature. The revealed switching regime suppresses electrostatic interaction of neighboring domains and leads to a significant improvement of the domain structure regularity. The creation of the stable periodical domain structure with submicron periods in SPE CLN planar waveguides was demonstrated.