Search

A series of Bi 0.5- x Er x Na 0.4 K 0.1 TiO 3 (BNKT- x Er) ceramics were designed and fabricated, the dopant effects on dielectric, piezoelectric and photoluminescence properties were studied. The results show that the piezoelectric property of BNKT can be enhanced by a trace amount of Er dopant, which is also reflected in the large linear electrostrain (S uni = 0.29%, under 55 kV/cm) achieved in BNKT-0.0025 Er. On the other hand, higher Er content can produce excellent dielectric temperature stability, with △ ԑ / ԑ 150 °C < ±15% over temperature range of 90∼510 °C. Meanwhile, all BNKT- x Er ceramics exhibit good photoluminescence properties, which may open new applications of these multifunctional ceramics. [ABSTRACT FROM AUTHOR]

Micrometre-sized pure BiFeO 3 (BF) and Ce-doped Bi 0.9 Ce 0.1 FeO 3 (BCF) powders were synthesized by using conventional hydrothermal (H) and microwave assisted hydrothermal (MH) methods. The BF-H and BCF-H show obviously enhanced weak ferromagnetic characteristic, in which the BCF-H exhibits excellent magnetic performance, with significantly increased maximum magnetization of ∼3.6 emu/g (under 50 kOe magnetic field) and remanent magnetization of ∼0.268 emu/g at room temperature. The superior magnetic property of BCF-H could be attributed to the suppression of spiral structure and the modulation of canting angle of spins in antiferromagnetic sublattices. [ABSTRACT FROM AUTHOR]

In this study, (1- x)(0.66Bi 0.5 Na 0.5 TiO 3 –0.34Bi 0.2 Sr 0.7 TiO 3)– x K 0.5 Nd 0.5 TiO 3 (BNBST– x KNT) ceramics were designed and synthesized, and they present significantly enhanced dielectric temperature stability and energy storage properties. The BNBST–0.06KNT composition exhibits a remarkable dielectric stability, as reflected in its stable dielectric constant (△ ԑ / ԑ 150 °C < ±15%) over a broad temperature range (25–401 °C). BNBST–0.02KNT achieves a high energy storage density W rec = 1.2 J/cm3 under 110 kV/cm with an energy storage efficiency η of 76.9%, and the improved energy storage property originates from the improved breakdown field strength and decreased hysteresis behavior. The electrical conductivity and relaxation behaviors of BNBST– x KNT were also analyzed via impedance spectroscopy. [ABSTRACT FROM AUTHOR]

A ternary solid solution of Bi 0.5 Na 0. 5 TiO 3 –Bi 0.5 K 0. 5 TiO 3 –Bi(Mg 2/3 Ta 1/3)O 3 (BNKT- x BMT) lead-free electroceramics was synthesized by a solid-state reactive sintering technique. The electrostrain, dielectric, and ferroelectric properties as well as the impedance characteristics and the microstructure were systematically assessed. With the increase of BMT, the BNKT- x BMT ceramics gradually transformed from non-ergodic relaxor phase to ergodic relaxor phase, manifested as the ferroelectric-to-relaxor temperature (T F-R) shifts towards below room temperature. Additionally, the ferroelectric hysteresis curves became pinched, and the strain curve changed from butterfly-shaped into sprout-shaped. At the ergodic relaxor composition of x = 0.04, a large electrostrain value (S = 0.4%; under an electric field of 60 kV/cm, d 33 * = 632 pm/V) was achieved, which is mainly attributed to the electric-field-induced transition from the ergodic relaxor phase to the ferroelectric phase. [ABSTRACT FROM AUTHOR]

Abstract A novel sandwich-like g-C 3 N 4 /PPy nanocomposite based on the integration of polypyrrole (PPy) onto the surfaces of layered g-C 3 N 4 nanosheets has been successfully fabricated through a chemical oxidation method. The obtained g-C 3 N 4 /PPy nanocomposite exhibits large specific surface area and high specific capacitance, cyclic reliability and rate capability characteristics. The specific capacitance reaches 471 F g−1 at current density of 1A·g−1, remaining >80% of its original value with cycling up to 1000 times or at the current density of 20 A g−1, while still remaining >71% with cycling up to 5000 times. As a potential electrode material for supercapacitor, the unique sandwich-like g-C 3 N 4 /PPy nanostructure not only benefits the diffusions of ions and electrons during the electrochemical reaction, but also releases the stress generated by the PPy's volume changes during charge and discharge, leading to the improved cyclic reliability. [ABSTRACT FROM AUTHOR]

Abstract: The (1−x)(0.8Bi1/2Na1/2TiO3–0.2Bi1/2K1/2TiO3)−xBiMg2/3Nb1/3O3 (100xBMN) ternary solid solutions were designed and prepared using a conventional solid‐state reaction. Temperature and compositional dependent ferroelectric, piezoelectric, dielectric features, and structural evolution were systematically studied. At the critical composition of 2BMN, a large bipolar strain of 0.43% was achieved at 55 kV/cm, and the normalized strain reaches to 862 pm/V at a low driving electric field of 40 kV/cm. It was found that the substitution of BiMg2/3Nb1/3O3 induces a transformation from ferroelectric to relaxor phase by disrupting the long range ferroelectric order. Therefore, as the external electric field was applied, a relaxor‐ferroelectric phase transition will be induced. This is contributed to the giant strain. The results above suggest that such a ternary composition is a promising candidate for application to actuator. [ABSTRACT FROM AUTHOR]

Ternary solid solutions of (1 − x)(0.8Bi0.5Na0.5TiO3-0.2Bi0.5K0.5TiO3)- xNaNbO3 (BNKT- xNN) lead-free piezoceramics were fabricated using a conventional solid-state reaction method. Pure BNKT composition exhibited an electric-field-induced irreversible structural transition from pseudocubic to ferroelectric rhombohedral phase at room temperature. Accompanied with the ferroelectric-to-relaxor temperature TF-R shifted down below room temperature as the substitution of NN, a compositionally induced nonergodic-to-ergodic relaxor transition was presented, which featured the pinched-shape polarization and sprout-shape strain hysteresis loops. A strain value of ~0.445% (under a driving field of 55 kV/cm) with large normalized strain of ~810 pm/V was obtained for the composition of BNKT-0.04 NN, and the large strain was attributed to the reversible electric-field-induced transition between ergodic relaxor and ferroelectric phase. [ABSTRACT FROM AUTHOR]

Polycrystalline Bi 1− x La x FeO 3 (BLF, x = 0.05–0.2) were prepared by solid state reaction and followed by annealing in O 2 , air and N 2 . The electrical properties of BLF ceramics were investigated by impedance spectroscopy and it is found that the conduction is dominated by p -type conduction. The conductivity of samples varies by several orders of magnitude, depending on the oxygen partial pressure during the annealing process. Activation energy ( E a ) increases from ∼0.5 eV for O 2 /air-annealed samples to ∼0.9 eV for the N 2 -annealed samples, and E a shows a slightly increase with the increment of La doping amount. Besides, all the samples exhibit nonlinear current ( I )–voltage ( V ) characteristics, and the threshold field voltage is much higher for the N 2 -annealed samples than for the O 2 -annealed samples. The nonlinear coefficient increases with the increase of oxygen partial pressure and temperature as well as the decrease of the La doping amount. The intrinsic electrostatic barrier at the domain walls rather than grain boundaries is responsible for the nonlinear behavior. [ABSTRACT FROM AUTHOR]

Ferroelectric ceramic with a large electrocaloric (EC) effect at a very low electric field is very attractive in the next solid state refrigeration technology. In this work, two Pb(Sc 0.25 In 0.25 Nb 0.25 Ta 0.25)O 3 (PSINT) medium-entropy ceramics were successfully synthesized by a spark plasma sintering (SPS) technology, including one-step-SPS processed and two-step-SPS processed samples. A large EC effect (△ T ∼ 0.85 K) with a high EC strength (△ T /△ E ∼ 0.021 K cm/kV) around room temperature are obtained at a very low electric field (∼40 kV/cm) in the two-step-SPS processed sample. Moreover, the working temperature range is very broad (∼120 K), which can be responsible for the high relaxation degree of the dielectric peak. It can be believed that the PSINT medium-entropy ceramics can be promising candidates for application in the next-generation EC cooling devices. [ABSTRACT FROM AUTHOR]

Lead-free relaxor ferroelectric (RFE) ceramics find application in a broad range of technological devices due to their large electrostrain. But few lead-free ceramics show electrostrain values of more than 1 %. Here, an extraordinary strategy to obtain giant electrostrain by manipulating defect dipoles in (Bi, Na)TiO 3 -BaTiO 3 -based RFE ceramics is developed, achieving a high electro-induced strain value of 1.68 %, with a corresponding effective piezoelectric coefficient (d * 33) of 1965 pm/V. Furthermore, the effect of defect dipoles on RFE ceramics is discussed. The defects are pinned after poling, forming defect dipoles polarization (P d) oriented along or close to the poling direction. P d significantly promotes the transformation of polar nano regions to ferroelectric domains during strain-electric field (S - E) cycles, resulting in ultra-high electrostrain. This work proposes a detailed mechanism considering defect dipoles coupling in RFE ceramics and provides a promising paradigm for achieving high electrostrain, which could be applied in designing a wide range of functional ceramics. [ABSTRACT FROM AUTHOR]

Lead-free ferroelectric ceramics have aroused widespread concerns, due to their properties of rapid charge/discharge and electric-induced strain without harming the environment. However, compared with thin-film capacitors, ceramics have a larger energy loss. In addition, the large time lag between electric field and strain also reduces its accuracy as an actuator. Therefore, the relaxor ternary solid solution (BaTiO 3 –Bi 0.48 Na 0.48 La 0.03 TiO 3 –NaNbO 3) was constructed in this work, aiming to obtain large energy storage efficiency and low time delay. The strategy and optimization aim to improve the relaxation degree and reduce the maximum permittivity temperature to room temperature, building a special crossover region where high and low dynamic polar nano regions co-existence. Thus a recoverable energy density of 1.24 J/cm3 under a low electric field (135 kV/cm) and a high energy storage efficiency (96%) are obtained and low hysteresis electrostriction with a large electrostriction coefficient (Q 33 = 0.0367 m4/C2) is also achieved in this system. This work suggests that this system can be considered promising materials as high-efficiency capacitors and high-precision actuators. It also attracts interest in the basic research on the dynamic changes of polar nano regions. [ABSTRACT FROM AUTHOR]

(B 1/3 /Nb 2/3 ) (B=Mg, Zn, Cu) co-substituting for Ti 4+ in B-site of Bi 4 Ti 3 O 12 -based Aurivillius ceramics were prepared to improve the piezoelectric properties. The electrical properties and conduction mechanisms of them were investigated. The activation energy related with the electrical relaxation determined from the electric modulus spectra was 0.71 eV and the electrical conductivity decreased dramatically by (Mg 1/3 /Nb 2/3 )-doping, due to the enhanced structural distortion and the decrease in oxygen vacancy concentration. The (Mg 1/3 /Nb 2/3 )-substituted specimen with a Curie point of 686 °C and a large field-induced strain of 0.061% as well as a higher remnant polarization of 12.9 μC/cm 2 could be a promising material for high-temperature lead-free piezoelectric applications. [ABSTRACT FROM AUTHOR]

In order to hunt for the promising materials in energy-storage field, we prepared a series of compositions Bi 0.487 Na 0.427 K 0.06 Ba 0.026 TiO 3 - x CeO 2 (BNTC1000 x , x = 1.8, 2.2, 2.6, 3.0 wt%) by the solid–state reaction method. CeO 2 addition degraded the ferroelectricity of initial components and all these samples exhibited antiferroelectricity at room temperature. The optimum energy-storage density of 0.94 J/cm 3 was obtained at BNTC22 with the external electric field of 75 kV/cm. In addition, the energy-storage property not only possessed good temperature stability but also maintained high values over 0.81 J/cm 3 around 20–120 °C. These characteristics indicated that Bi 0.487 Na 0.427 K 0.06 Ba 0.026 TiO 3 - x CeO 2 system could be the promising lead-free materials for energy-storage capacitor application. The investigation on dielectric properties suggested that the dielectric relaxation behavior was involved in BNTC1000 x system and concerned with oxygen vacancy migration. [ABSTRACT FROM AUTHOR]

Magnetic tunnel junctions have been widely used in various applications, such as magnetic sensors and magnetic random-access memories. In the practical application of MTJs, they are usually used in series toward high sensitivity and high stability, especially for sensor applications. In this paper, serial MTJs devices on 8 in. wafers were fabricated. The temperature dependence of the tunnel magnetoresistance ratio, resistances in parallel and antiparallel configurations, and dynamic conductance were systematically investigated. The results of serial MTJs devices are consistent with a single MTJ device. This research suggests that serial MTJs can be directly used to investigate the magnetic tunneling properties of MTJ stacks. [ABSTRACT FROM AUTHOR]

Abstract: A one-pot simple and cost-effective calcination method has been developed for preparing nanoroded zinc oxide (ZnO) with greatly enhanced photocatalytic activity. The nanocatalyst possessing smaller surface area synthesized by calcining zinc acetate dehydrate, however, acquired higher normalized rate constant than other reported ZnO nano/micromaterials. The samples characterized by XPS spectra denoted the photocatalytic activity enhancement might associate with oxygen vacancies. Notably, the ZnO nanorods were chemically stable and could be easily recycled for four times without obvious decrease in photocatalystic activity. This simple, cost-effective, high-yield method with excellent performance of resulting products could be extended to study oxygen vacancies and also provide new avenue for potential industrial applications. [Copyright &y& Elsevier]

Na 0.5 Bi 0.5 TiO 3 -based solid solutions are one of the most promising lead-free piezoelectric candidates since they can be easily tailored to exhibit large electrostrain. However, the large hysteresis and temperature-dependence of the electrostrain response are longstanding obstacles for their practical applications. In the present study, 0–3 type composites were developed with 0.97(0.94Na 0.5 Bi 0.5 TiO 3 -0.06BaTiO 3)-0.03AgNbO 3 (NBT-6BT-3AN) matrix phase and ZnO inclusions. The optimum addition of 5 wt.% ZnO in the composites leads to reduction in hysteresis of electrostrain by 35% in comparison with pure NBT-6BT-3AN at room temperature. Meanwhile, electrostrain of the composites maintains superior temperature stability, with a variance of less than ±10% in the temperature range between 25 and 125 °C. The reason for the improvement of electrostrain is proposed to be attributed to the ergodic/nonergodic mixture phases induced by residual stress between the inclusion and matrix, as well as the phase evolution caused by the incorporation of Zn2+ into the matrix. Therefore, this work provides a new strategy to improve the electromechanical properties of Na 0.5 Bi 0.5 TiO 3 -based ceramics. [ABSTRACT FROM AUTHOR]

(1- x)[0.94(Bi 0.5 Na 0.5)TiO 3 -0.06BaTiO 3 ]- x Ba(Sn 0.70 Nb 0.24)O 3 (abbreviated as BNTBT-100 x BSN) lead-free ceramics were fabricated with a relative density greater than 96 %, and the structure as well as performance were tested. BNTBT-100 x BSN ceramics are pseudo-cubic perovskite structure, with dense surface morphology. Doping BSN can effectively reduce the dielectric loss of ceramics and increase the relaxation properties to a certain extent. The randomly distributed ferroelectric phase was replaced by polar nano regions, thereby improving the electro-strain and energy storage performance of the system. The largest electro-strain and the corresponding normalized strain (d 33 *) reach ~ 0.43 % and 633 pm/V respectively in the BNTBT-1BSN ceramic. The largest effective energy storage density reaching ~ 1.28 J/cm3 was tested in BNTBT-2BSN. BNTBT-100 x BSN ceramics provide a feasible idea for the systematic research of lead-free ferroelectrics and improvements in electro-strain and energy storage applications. [ABSTRACT FROM AUTHOR]

A series of novel Bi 0.38 Na 0.38 Sr 0.24 Ti (1- x) (Mn 1/3 Nb 2/3) x O 3 lead-free ceramics (BNST-100 x MN) were designed and fabricated. The dielectric, ferroelectric, energy-storage, electrostrain properties, and impedance performance of these materials were systematically investigated. A large strain response under low driving electric field was obtained that benefits from the enhanced relaxor-to-ferroelectric phase transition. The optimum piezoelectric stain coefficient d 33 * of 930 pm/V (under 40 kV/cm) was achieved in BNST-1MN composition. The substitution by MN dopant gave rise to a homogeneous micro-morphology with small grains that gave rise to an enhanced high breakdown strength (BDS). Slim and slanted ferroelectric hysteresis was obtained by introducing a larger amount of MN, and hence the BNST-2MN ceramic exhibits a high energy-storage density of 1.30 J/cm3 at 110 kV/cm, accompanied with an excellent fatigue-free behavior. The dielectric response exhibited a stable high temperature dielectric property with low dielectric loss. These results indicate that BNST-100 x MN ceramics are promising candidates for the actuator and energy storage applications. [ABSTRACT FROM AUTHOR]

Graphite carbon nitride (g-C 3 N 4) is an appealing metal-free photocatalyst for hydrogen evolution, but the potential has been limited by its poor visible-light absorption and unsatisfactory separation of photo-induced carriers. Herein, a facile one-pot strategy to fabricate carbon self-doped g-C 3 N 4 composite through the calcination of dicyanamide and trace amounts of dimethylformamide is presented. The as-obtained carbon self-doped catalyst is investigated by X-ray photoelectron spectroscopy (XPS), confirming the substitution of carbon atoms in original sites of bridging nitrogen. We demonstrate that the as-prepared materials display remarkably improved visible-light absorption and optimized electronic structure under the premise of principally maintaining the tri- s -triazine based crystal framework and surface properties. Furthermore, the carbon doped g-C 3 N 4 composite simultaneously weakens the transportation barrier of charge carriers, suppresses charge recombination and raises the separated efficiency of photoinduced holes and electrons on account of the extension of pi conjugated system. As a result, carbon self-doped g-C 3 N 4 exhibits 4.3 times greater photocurrent density and 5.2 times higher hydrogen evolution rate compared with its bulk counterpart under visible light irradiation. [ABSTRACT FROM AUTHOR]

Polycrystalline (1- x)[(Na 0.5 Bi 0.5) 0.95 Ba 0.05 ] 0.98 La 0.02 TiO 3 - x K 0.5 Na 0.5 NbO 3 systems were prepared using the solid-state reaction technique. Modification of (Na 0.5 Bi 0.5) 0.95 Ba 0.05 ] 0.98 La 0.02 TiO 3 ceramic with a proper amount of K 0.5 Na 0.5 NbO 3 can effectively improve the temperature-stable of dielectric properties. A variation in dielectric constant is maintained smaller than ±5% from 80 to 300 °C accompanied with a low dielectric loss (≤0.04). The relaxor properties of the doped samples are significantly enhanced. A high energy storage density of 1.1 J/cm3 and efficiency ~80% at 90 kV/cm are achieved in the x = 0.05 composition. Hence, the as-prepared ceramics might be practical in dielectric constant which can work stably at a high temperature range and pulsed capacitors. [ABSTRACT FROM AUTHOR]

Abstract Nanoscale transition metal oxides and polyoxometalates attract great attention due to their short diffusion channel distance and reversible redox reaction. However, the inevitable agglomeration, shrinkage and volumetric expansion/shrinkage of nanomaterials seriously affect their electrochemical properties. Here, the 3D heterostructure CoWO 4 /Co 3 O 4 nanocone arrays are synthesized via a facile and efficient microwave hydrothermal method. The obtained CoWO 4 /Co 3 O 4 NCAs overcome these shortcomings and achieve high electrochemical performance. The electrochemical behaviors of as-prepared composites are investigated systematically, during which four pairs of redox peaks in cyclic voltammetry curve are observed and discussed in detail. The kinetic analysis of redox reaction is employed to confirm the redox pseudocapacitance mechanism (surface capacitance-dominated process) and intercalation pseudocapacitance mechanism (diffusion-controlled process) of charge storage, suggesting faradaic intercalation process of 3D heterostructure CoWO 4 /Co 3 O 4 NCAs (22% diffusion contribution at 0.8 mV s−1). The assembled solid-state hybrid supercapacitors further exhibit high energy density (45.6 Wh kg−1) and power density (7500 W kg−1 at 32.8 Wh kg−1) even at a super-high total loading mass of 23.1 mg of active materials. This work provides some meaningful and significant basis and foundation for the study of supercapacitors. Graphical abstract Image 1 Highlights • Four pairs of redox peaks were observed in CV curve and analyzed systematically. • The contribution of pseudocapacitive were quantified. • Solid-state supercapacitors exhibited a superior energy density at high loading mass. [ABSTRACT FROM AUTHOR]

A series of (1- x )(0.7Bi 0.5 Na 0.5 TiO 3 -0.3Bi 0.2 Sr 0.7 TiO 3 )- x NaNbO 3 (BNT-BST-100 x NN) lead-free ceramics were fabricated using conventional solid-state reaction technique. The phase behavior, microstructure, dielectric, ac impedance and energy-storage properties of the sintered ceramics were systematically investigated. XRD patterns and surface SEM micrographs revealed the introduction of NaNbO 3 didn't change the perovskite structure of BNT-BST at low doping level. The NaNbO 3 doping gave rise to slimmer P - E loops and thus gained enhanced energy storage properties. Therefore, a maximum energy storage density of 1.03 J/cm 3 was achieved at 85 kV/cm at x = 0.01 via increasing the dielectric breakdown strength (DBS). Temperature-dependent dielectric permittivity illustrated the enhanced relaxor characteristics, implying the long-rang ferroelectric order was further damaged due to the introduction of NaNbO 3 . The results above indicate the sintered ternary ceramics can be a promising lead-free candidate for energy storage capacitors. [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride (g-C 3 N 4 )/ZnO nanosheets were coated on the surface of fluorine-doped tin oxide (FTO) glass as a noble metal-free g-C 3 N 4 /ZnO/FTO electrode, which was used for the determination of hydrogen peroxide (H 2 O 2 ). The exfoliated g-C 3 N 4 nanosheets were firstly prepared and then ZnO nanosheets were grown on g-C 3 N 4 nanosheets by a microwave-assisted hydrothermal synthesis. The g-C 3 N 4 nanosheets combined with ZnO nanosheets can greatly improve the adsorption of hydrogen peroxide and increase the conductivity of materials as well. The g-C 3 N 4 /ZnO nanosheets were characterized by powder X-ray diffraction (XRD), scanning electron microscopic (SEM), transmission electron microscopic (TEM), and X-ray photoelectron spectroscopy (XPS) analysis. Meanwhile, electrochemical measurements of the g-C 3 N 4 /ZnO/FTO electrode were utilized to investigate the amperometric sensing of hydrogen peroxide. The prepared g-C 3 N 4 /ZnO/FTO electrode revealed the sensitivity of 540.8 μA mM −1 cm −2 at −0.5 V with the linear response range from 0.05 to 14.15 mM, which even was superior to some noble metal-decorated H 2 O 2 sensors. Additionally, the g-C 3 N 4 /ZnO/FTO electrode also showed the reliable operational and environmental stability for electrochemical reduction of H 2 O 2 . [ABSTRACT FROM AUTHOR]

We report a giant strain (0.72%) with a low degree of hysteresis ( ca . 36.2%) and a giant S max / E max ratio (916 pm V −1 , S max and E max denote the maximum strain and the corresponding electric field, respectively) for lead-free (1− x )(0.8Bi 0.5 Na 0.5 TiO 3 -0.2Bi 0.5 K 0.5 TiO 3 )- x Sr 0.8 Bi 0.1 □ 0.1 Ti 0.8 Zr 0.2 O 2.95 piezoceramics with x = 0.06. The giant strain originates from a reversible transition between the ergodic relaxor and ferroelectric states under applied electric fields. A-site vacancies (V A ) and oxygen vacancies (V O ), deliberately introduced to the system, induce a randomly distributed local polarization field. The local field induces embryonic polarization domains that have a broad distribution of maturity and thus smears the transition between the ferroelectric and relaxor states. This leads to a narrow hysteresis loop. The poling field required for the relaxor-to-ferroelectric transition is reduced significantly, due to the remanent ferroelectric phase at zero field acting as the seed, and the point defects synergistically facilitating the nucleation and growth of the ferroelectric phase. Our work provides a novel route for designing piezoelectric materials with both a giant strain and a narrow hysteresis for practical actuator applications. [ABSTRACT FROM AUTHOR]

Two-dimension layered polymeric carbon nitride possessing unique electronic structure and high specific surface area exhibits immense potentials for visible light driven photocatalytic activity for hydrogen production by the decomposition of water molecules. Herein, porous polymeric carbon nitride nanosheets were obtained by lithium chloride ions in situ intercalating bulk materials in thermal polycondensation process and followed by liquid exfoliation in water. The porous nanosheets show two-dimension layered structure with the thickness of 2–3 nm, a high density in-plane pores with 2–3 nm diameter, a higher surface area (186.3 m 2 g −1 ), enlarged bandgap (by 0.16 eV), prolonged charge carrier lifetime, enhanced electronic transport ability, increased charge carrier density and improved photocurrent responses, which could significantly give rise to photocatalytic activity. The results highlight the crucial role of 2D porous structure, high specific surface area and unique electronic structure on the photocatalytic performance of polymeric carbon nitride materials. [ABSTRACT FROM AUTHOR]

The 0.94Bi 0.5 Na 0.5 TiO 3 –0.06BaTiO 3 (BNBT6) introduced by CaZrO 3 (CZ) lead-free ferroelectric ceramics are successfully fabricated by conventional solid state reaction. The influence of CZ substitution on the phase transition, microstructure, dielectric, ferroelectric, and energy storage properties of (1 − x)BNBT6-xCZ ceramics are systematically investigated. The energy-storage density 0.7 J/cm 3 under the electric field 70 kV/cm is obtained in the 0.97BNBT6-0.03CZ. In addition, its energy-storage property exhibits thermal stability at the temperature range of 30–130 °C. [ABSTRACT FROM AUTHOR]

Large energy-storage density is observed in BaZrO (BZ)-modified 0.80BiNaTiO-0.20BiKTiO (BNBK) lead-free ferroelectric (FE) ceramics synthesized by conventional solid-state reaction. The energy-storage property of (1 − x)BNBK- xBZ has been investigated. Certain content of BZ can enhance the energy-storage property of BNBK by enhancing the breakdown strength. The largest energy-storage density W = 0.73 J/cm and efficiency of energy storage η = 0.75 at E = 70 kV/cm are achieved in the 0.96BNBK-0.04BZ, which is significantly higher than that of BNT-based and lead-containing FE materials reported. Its energy-storage density exhibits the superior thermal stability with temperature range of 30-100 °C. Those properties promise that the environmental friendly (1 − x)BNBK- xBZ ceramics are candidate for applications of energy-storage devices. [ABSTRACT FROM AUTHOR]

Pure perovskite K0.5Na0.5NbO3- xSrTiO3 ( x = 0.16, 0.17, 0.18, and 0.19) ceramics were prepared by using a solid-state reaction process. The ceramics were optically transparent for visible and near-infrared wavelengths. Then, high tunability (24.1%) and low dielectric loss (0.016) for the x = 0.18 sample indicated the transparent ceramics could be used in tunable devices. The Lorentz-type relation fitting for the temperature dependence of dielectric permittivity showed that these ceramics had a typical relaxor behavior, and the polar nanoregions were related to the tunable dielectric properties. The nonlinear dielectric behavior was further explored by the Johnson model combined with Langevin terms, which revealed that the polar nanoregions contributed to the nonlinear ε( E) dependencies with contributions of 12.3%, 11.6%, 5.9%, and 3.6% for x = 0.16, 0.17, 0.18, and 0.19, respectively. [ABSTRACT FROM AUTHOR]

Dye-sensitized solar cells (DSSCs) were fabricated based on different ZnO nanostructures with controllable morphologies synthesized via capping agent-assisted hydrothermal method. The capping agent hindered the growth along (001) direction, so the morphology evolved from rods to nanosheets with increasing the amounts of capping agents. The kinetics of the photoelectrochemical properties in DSSCs were also evaluated via electrochemical impedance spectroscopy with focusing on exploring the electron lifetime, electron diffusion coefficient and effective diffusion length of the cells in a quantitative manner based on an equivalent circuit model. The physical properties, such as specific surface area, photoluminescence and ultraviolet–vis diffuse reflectance spectra (DRS), were also extensively characterized in detail. DSSCs fabricated with ZnO nanosheets/rod hierarchical structures as photoanodes showed significantly improved photovoltaic performance with open-circuit voltage increasing from 0.45 V to 0.73 V, as well as the overall conversion efficiency 5.69 times better than that of ZnO rod. It was attributed to higher surface area (21.96 m 2 ·g − 1 ) and more efficient light absorption, as well as more efficient electron transfer process. [ABSTRACT FROM AUTHOR]

Bismuth and niobium co-substitutions on lanthanum molybdate with the nominal formula La 2− x Bi x Mo 2− x Nb x O 9− δ ( x = 0–0.24) (LBMN) are synthesized via solid state reaction. Their structures and properties are studied by powder X -ray diffraction (XRD), thermal analysis, electron diffraction, and impedance spectroscopy. XRD experiments and thermal analysis demonstrate the stabilization of the high temperature cubic phase when x ≥ 0.04. Studies of the polar area in electron diffraction confirm the inhomogeneous nature of the composition. A modified Debye relaxation approach is employed to learn the ion dynamics, and it shows non-monotonic functions in relaxation parameters τ 0 and the activation energy E a , which is in agreement with the volume variation of the basic [O1La3Mo] tetrahedral as a new structural description. As a result, the LBMN system exhibits good performance in electrical conductivities at high temperature, and shows a decrease of the average thermal expansion coefficients (TECs) along the dopant content. [ABSTRACT FROM AUTHOR]

Highlights: [•] K0.5Na0.5Nb0.99Mg0.01O2.985 crystallized in the orthorhombic space group Bmm2. [•] P–E loops of K0.5Na0.5Nb0.99Mg0.01O2.985 were studied after annealing and aging. [•] Defect dipoles and polarization were elaborated in K0.5Na0.5Nb1−xMg x O3−3x/2. [ABSTRACT FROM AUTHOR]

The effect of Mg2+/Nb5+ co-substitution at the B-site on the structures and electrical properties of modified Aurivillius ceramics, Bi4Ti3− x (Mg1/3Nb2/3) x O12, was investigated. Rietveld refinement suggested that Bi4Ti3− x (Mg1/3Nb2/3) x O12 crystallized in the orthorhombic space group B2cb at room temperature. A high remnant polarization of 15.5μCcm−2, a large field-induced strain of 0.068% and a high piezoelectric activity of 30pCN−1 were observed in Bi4Ti2.95(Mg1/3Nb2/3)0.05O12, with a Curie point of 685°C, due to an enhancement in structural distortion and a reduction in leakage current. [ABSTRACT FROM AUTHOR]

• The doping of Li+ ion has an obvious influence on the strain and energy storage performance. • The TEM image and XPS spectra of O 1s for BNKTT-100xLi ceramics demonstrate the existence of PNRs and oxygen vacancies. • The maximum bipolar strain (S = 0.462%) and unipolar strain (S u = 0.443%) for x = 0.025 sample were obtained under 80 kV/cm, and its unipolar strain achieved 0.573% at 100 °C. • BNKTT-15Li ceramic exhibited outstanding energy storage performance with a recoverable energy density of 1.29 J/cm3 under applied 130 kV/cm field. The conventional solid reaction was used to synthesize (Na 0.8- x K 0.2 Li x) 0.5 Bi 0.5 Ti 0.985 Ta 0.015 O 3 (abbreviated as BNKTT-100 x Li) lead-free perovskite ceramics. The influences of Li+ ion doping for the relaxation mechanism and piezoelectric performances of all ceramics were systematically investigated. All ceramics exhibited a single perovskite structure, accompanied with a dense surface morphology and uniform element distributions. AC impedance spectroscopy showed the single grain conduction mechanism for all samples. The maximum bipolar strain (S = 0.462%) and unipolar strain (S u = 0.443%) for x = 0.025 sample were obtained under 80 kV/cm, and its unipolar strain achieved 0.573% at 100 °C. BNKTT-15Li ceramic exhibited outstanding energy storage performance with a recoverable energy density of 1.29 J/cm3 under applied 130 kV/cm field. It suggested that the excellent electro-strain and energy-storage properties for BNKTT-100 x Li ceramics could be widely applicable to electronic equipment. [ABSTRACT FROM AUTHOR]

[Display omitted] • The flexible substrate of polyethylene terephthalate fibers was modified by the ethylenediamine to expose amino group. • The positive amino group could effectively attract with carboxyl of multi-walled carbon nanotubes. • The PET-NH 2 -MCNTs/PANI sensor exhibited good ammonia sensing at room temperature. The flexible room-temperature gas sensors are highly desirable to apply in wearable and portable equipment owing to their wearability. The research mainly focuses on the gas-sensing materials and few studies paid attention to the conjunction between flexible substrates and sensing materials. In this work, the polyethylene terephthalate (PET) fibers substrate is modified by ethylenediamine (EDA) to expose the amino group on the surface (PET-NH 2). This method is simple, cost-efficient, and easy to operate. The positively charged amino group could interact with negatively charged carboxyl (−COOH) of multi-walled carbon nanotubes (MWCNTs) by electrostatic attraction. The EDA treatment on PET effectively strengthens the connection between the flexible PET substrate and gas sensing materials with carboxyl as evidenced by SEM images. After the in situ polymerization process, the polyaniline (PANI) is successfully decorated on the MWCNTs. The fabricated PET-NH 2 -MWCNTs/PANI sensor exhibits strongly enhanced ammonia (NH 3) sensing performance as compared to the PET-MWCNTs/PANI sensor without the EDA treatment. The results suggest that the EDA treatment is an effective method to conjunct between flexible substrates and sensing materials, which shows great potential in the field of flexible gas sensors. [ABSTRACT FROM AUTHOR]

Co 3 O 4 has been extensively studied for its ultra-high theoretical specific capacitance (3560 F g−1) and cost-effectiveness. However, its poor conductivity originating from the relatively wide band gap, results in a low specific capacitance, a low energy density and a poor rate performance. In order to improve the rate performance of Co 3 O 4 , an in situ formed Co@Co 3 O 4 structure was assembled with a post-heat treatment. Therein, Co nanosheet arrays (NSAs) were deposited on the activated carbon cloth (ACC) with a simple electrodeposition method. The Co@Co 3 O 4 core-shell structure was characterized with XRD, HRTEM and XPS after argon ion etching. In addition, the kinetic analysis of redox reaction was introduced to quantify the contribution of redox pseudocapacitance and intercalated pseudocapacitance ("battery-type" materials). The Co@Co 3 O 4 nanosheets show a high specific capacitance of 1520 F g−1 at 1 A g−1 and the specific capacitance retention at 10 A g−1 takes 80.3% of the value at 1 A g−1. The assembled hybrid supercapacitors (HSCs) show a superb energy density (60 Wh kg−1) as well as a long lifespan (82.6% of the initial value after 10000 cycles). The eminent performance stems from the synergistic effect of Co@Co 3 O 4 core-shell nanostructure, ensuring the structural stability and the rapid transmission of electrons. In situ synthesis of 3D Co@Co 3 O 4 nanosheet arrays possessed high specific capacitance of 1520 F g−1 at 1 A g−1 as well as outstanding rate performance Moreover, the contribution of various pseudocapacitive was quantified. Image 1 • A simple in-situ synthesis method of Co@Co 3 O 4 was proposed. • The framework of Co conductive array combined with Co 3 O 4 shell formed a collective network for ultrafast electron transport. • The contribution of different pseudocapacitive were quantified. • Hybrid supercapacitors exhibited a superior high-rate performance and energy density. [ABSTRACT FROM AUTHOR]