Search

Electrochemical conversion of CO2 to highly valuable ethanol has been considered a intriguring strategy for carbon neutruality. However, the slow kinetics of coupling carbon‐carbon (C−C) bonds, especially the low selectivity ethanol than ethylene in neutral conditions, is a significant challenge. Herein, the asymmetrical refinement structure with enhanced charge polarization is built in the vertically oriented bimetallic organic frameworks (NiCu‐MOF) nanorod array with encapsulated Cu2O (Cu2O@MOF/CF), which can induce an intensive internal electric field to increase the C−C coupling for producing ethanol in neutral electrolyte. Particularly, when directly employed Cu2O@MOF/CF as the self‐supporting electrode, the ethanol faradaic efficiency (FEethanol) could reach maximum 44.3 % with an energy efficiency of 27 % at a low working‐potential of −0.615 V versus the reversible hydrogen electrode (vs. RHE) using CO2‐saturated 0.5 M KHCO3 as the electrolyte. Experimental and theoretical studies suggest that the polarization of atomically localized electric fields derived from the asymmetric electron distribution can tune the moderate adsorption of *CO to assist the C−C coupling and reduce the formation energy of H2CCHO*‐to‐*OCHCH3 for the generation of ethanol. Our research offers a reference for the design of highly active and selective electrocatalysts for reducing CO2 to multicarbon chemicals. [ABSTRACT FROM AUTHOR]

Currently semiconductor-based near ultraviolet and ultraviolet self-powered photodetectors usually display low detectivity and responsivity due to weak photogenerated electron and hole separation ability and not suitable electrode. BaTiO 3 possesses a high depolarization electric field throughout the bulk and wide band gap (> 3 eV), and hence is a good candidate for fabricating near-ultraviolet and ultraviolet self-powered photodetectors. Cu nanowires (NWs) have been regarded as promising transparent electrode for photodetectors because they have not only equivalent optical transparency and electrical conductivity relative to Ag NWs currently in use, but also far lower cost. But, weak resistance to oxidation in the environment of light and electricity prevents large-scale use of Cu NWs in photodetectors. Herein, an organic corrosion inhibitor, benzotriazole (BTA), is used to passivate Cu NWs, and interestingly, the passivated NW networks exhibit significantly increased resistance to oxidation. At zero field, the BaTiO 3 photodetector coated with Cu@BTA NWs exhibits stable photocurrent, high responsibility of 6.45 × 10−7A/W, large detectivity of 1.97 × 108 Jones, and fast response rate (rise and decay time being 28.8 ms and 37.2 ms, respectively) at the wavelength of 405 nm, which is far better than indium-tin-oxide electrode-coated BaTiO 3 photodetector. This work provides a strong guideline for large-scale fabrication of low-cost and high-stability transparent electrodes applicable in near-ultraviolet and ultraviolet photoelectric devices. [ABSTRACT FROM AUTHOR]

Recently, the progress of electronic devices toward miniaturization has strongly promoted development of multifunctional materials possessing multiple desirable properties. In this study, we develop and fabricate 0.93Bi 0.5 Na 0.5 TiO 3 -0.07BaTiO 3 - x Er multifunctional ceramics which show simultaneously considerable electric-field-induced strain and bright green light emission properties. With the introduction of Er3+, the ceramics gradually transform from non-ergodic relaxor phase to ergodic relaxor phase which could reversibly transform to ferroelectric phase under the electric field. As a result, with improving Er3+ content, the shape of the polarization-electric field loops of the ceramics become pinched, and it is obvious that the negative strain disappears while the positive strain gradually increases and reaches a maximum value 0.46% at x = 1.2 mol%. Besides, After the ceramics are poled, the light emission peak are greatly enhanced attributed to the decreased crystal symmetry and increased domain size, and is the strongest at x = 1.2 mol%. These results indicate that 0.93Bi 0.5 Na 0.5 TiO 3 -0.07BaTiO 3 - x Er ceramics are good candidates for developing multifunctional optoelectronic devices. [ABSTRACT FROM AUTHOR]

The effect of Sm addition on the crystal structures and electrical properties of Pb1-3x/2Smx(Zr0.63Sn0.26Ti0.11)O3 ceramics were investigated in this work. X-ray diffraction analysis showed that with increasing Sm content from 0.005 to 0.03, the phase structure of the specimens underwent transition from ferroelectric (FE) to antiferroelectric (AFE) state due to the substitution of Sm3+ with smaller ion radius for Pb2+ decreasing the tolerance factor of the ceramics. In addition, it was observed that with the improvement of Sm3+ content, the strain of the specimens first increased and then decreased, and the largest value of 0.735% was obtained in the sample with x = 0.015 near AFE/FE phase boundary at the measuring frequency 1 Hz. This is because the reversal of the domains, which produces the strain, is more consummate in this composition. Further, the strain at different frequencies was nearly the same at high electric field, which was attributed to that the electric field applied to the sample was so large that the reorientation of the domains could finish in all measuring frequencies. Both a high strain level and a relatively good frequency stability in the specimen with x = 0.015 make a potential candidate for actuators applications over a wide-frequency working range. [ABSTRACT FROM AUTHOR]

0.75(Na0.5Bi0.5)TiO3–0.25SrTiO3 lead‐free incipient piezoceramic is a promising candidate for actuator applications due to their large reversible electromechanical strains at the relatively low driving field of 40 kV/cm. In order to further reduce the driving field of 0.75(Na0.5Bi0.5)TiO–0.25SrTiO3 relaxor ceramic to meet the requirements for real actuators application, the relaxor/ferroelectric (RE/FE) 0‐3 composite ceramics method was employed. The polarization and strain behaviors were examined as a function of the weight ratio of the relaxor/ferroelectric phases. It was found that 90 wt% 0.75(Na0.5Bi0.5)TiO3–0.25SrTiO3/10 wt% 0.96(Na0.84K0.16)1/2Bi1/2TiO3–0.04SrTiO3RE/FE 0‐3 type composite samples provided a high unipolar strain of 0.25% and the corresponding large‐signal piezoelectric coefficient, d*33 of 833 pm/V at 30 kV/cm, which are 32% higher than the values of the pure 0.75(Na0.5Bi0.5)TiO3–0.25SrTiO3. The enhanced electric‐field‐induced strain at relatively lower field was attributed primarily to the reduction in the RE‐FE phase transition electric field. It was also found that the RE/FE composite ceramics exhibited significantly reduced frequency dependence in the unipolar strain behavior at room temperature. [ABSTRACT FROM AUTHOR]

Bi 0.5 Na 0.5 TiO 3 -based lead-free piezoceramics with large strain output are of great importance in the application of piezoelectric actuators. AgNbO 3 -modified 0.76Bi 0.5 Na 0.5 TiO 3 -0.24SrTiO 3 (BNT-24ST) lead-free piezoceramics were synthesized by conventional solid-state reaction method. The effects of AgNbO 3 on the structures, dielectric, ferroelectric and piezoelectric properties were carefully investigated. A large electrostrain and normalized strain ( d 33 * = S max / E max ) of 0.27% and 700 pm/V, were obtained respectively at low electric field (40 kV/cm) for 1 mol.% AgNbO 3 -doped BNT-24ST. AgNbO 3 doping modified the phase composition which contained moderate amounts of tetragonal and rhombohedral phase by shifting its T F-R to below room temperature. Moreover, the reversible field-induced phase transition between relaxor and ferroelectric made contributions to its large strain related properties. This work has confirmed that the actuating performance of BNT-ST-based piezoceramics can be further improved by an easy and cost-effective composition engineering method and showed it a promising candidate for lead-free actuator material. [ABSTRACT FROM AUTHOR]

In order to obtain a new system of (Bi 1/2 Na 1/2 )TiO 3 (BNT) based lead-free incipient piezoceramics with large strain for practical applications of actuators, we investigated the effect of B-site complex-ion (Fe 0.5 Nb 0.5 ) 4+ (FN)-doped Bi 1/2 (Na 0.82 K 0.12 ) 1/2 TiO 3 ceramics on the phase structure, dielectric, ferroelectric, piezoelectric and electric-field-induced strain properties. All samples exhibited single perovskite phase with pseudocubic symmetry. The room temperature electric-field-induced polarization ( P - E ) and strain ( S - E ) hysteresis loops indirectly illustrated ferroelectric-to-relaxor (FE-RE) phase transition. The increasing content of FN doping decreased the FE-RE phase transition temperature, T F-R to below room temperature and induced the reversible FE-RE phase transition, giving rise to a large strain of 0.462% with a normalized strain, d * 33 of 660 pm/V at a critical composition of x = 5. A fluctuation of the dielectric curve for BNKT-5 mol% FN ceramics in the spectra around 80 °C before and after polarization suggested that the large strain response can be induced via delicate mixing of the FE and RE phase. [ABSTRACT FROM AUTHOR]

<001> oriented 0.91BiNaTiO-0.06BaTiO-0.03(Na,K)NbO (BNT-BT-KNN) lead-free piezoceramics were fabricated by templated grain growth method. A high grain orientation degree (Lotgering factor F is 83 %) was achieved with 5 wt% BiNaTiO (BNT) template content and a maximum strain value of 0.226 % was observed, which was 48.7 % higher than that of randomly oriented samples. However, too much BNT template will result in composition deviation from morphotropic phase boundary of BNT-BT-KNN system and disruption of the non-polar phase at zero electric field. All textured samples with 1-10 wt% template addition showed enhanced strain and large signal piezoelectric coefficient $$d_{33}^{*}$$ without disrupting the non-polar phase at zero electric field. The enhanced electric-field-induced strain of the textured sample was primarily attributed to the facilitated phase-transition, which formed a long-range ferroelectric order along the <001> direction. [ABSTRACT FROM AUTHOR]

Crystal structure and electrical properties of MnO2-doped Pb0.97La0.02(Zr0.63Sn0.26Ti0.11)O3 antiferroelectric ceramic were studied in detail in this article. X-ray diffraction analysis showed that all specimens took on single tetragonal antiferroelectric structure, and antiferroelectric phase stability enhanced with the increase of MnO2 addition, which was because that the substitution of Mn2+ or Mn3+ with large ion radius for B-site Ti4+ decreased the tolerance factor of the ceramic. In addition, it was observed that different from Mn doping reducing Tm of ferroelectric ceramics, Tm of antiferroelectric ceramics increased with the addition of MnO2, which is for the reason that MnO2 addition enlarged the zone of antiferroelectric phase. Furthermore, by increasing MnO2 content, the strain first increased and then decreased. Meanwhile, the value improved obviously as the measuring frequency decreased. The largest electric field–induced strain of 0.65% was obtained in the specimen with 0.2 mol% MnO2 doping at the frequency of 1 Hz, which lay a foundation for preparing actuator with high strain energy density. [ABSTRACT FROM PUBLISHER]

Abstract: (Pb0.97Ba0.02)Nb0.02(Zr0.55Sn0.45−x Ti x )0.98O3 (PBNZST, 0.03≤x≤0.06) ceramics were prepared by conventional solid state synthesis and their crystal structure, ferroelectric, dielectric, and electric field-induced strain properties were systemically investigated. A transformation from antiferroelectric (AFE) phase to ferroelectric (FE) phase was observed at 0.05

(PbLaBa)(ZrSnTi)O (PLBZST, 0.06≤ x≤0.09) antiferroelectric ceramics were fabricated by conventional solid state reaction process, and their ferroelectric, dielectric, and pyroelectric properties were systemically investigated. PLBZST with different Ti content were all confirmed to be in an antiferroelectric phase at T=50°C, which is close to the lowest phase transition temperature. Compared with conventional FE ceramics, PLBZST antiferroelectric ceramics exhibited higher electric field induced pyroelectric coefficient ( p). As the content of Ti increased from 0.06 to 0.09, the pyroelectric coefficient increased from 1000 to 6500 μC/mK under a 500 V/mm DC bias field. The maximum pyroelectric coefficient of 8400 μC/mK was obtained at x=0.09 when an 850 V/mm DC bias field was applied, which is far larger than that of conventional phase transition pyroelectric materials. Large pyroelectric response is beneficial for the development of infrared detectors and thermal imaging sensors. [ABSTRACT FROM AUTHOR]

Membrane structures, which are widely used in aerospace and civil engineering, are susceptible to large amplitude vibrations due to their low structural damping and high flexibility, leading to the degradation of their working performance. Strong electric fields are commonly needed for piezoelectric actuators to control larger amplitude vibration of membrane structures. However, the effect of piezoelectric nonlinearity due to strong electric fields on the control performance of membrane structures is still underexplored. Given the importance of piezoelectric nonlinearity due to strong electric fields, the present study aims to investigate the vibration control performance of piezoelectric actuators for membrane structures. First, based on the piezoelectric nonlinear constitutive equation, the actuation equation of the piezoelectric actuator is generated. Then, following D′Alembert's principle, a nonlinear dynamic control model of membrane structure containing actuation force is derived. Finally, active vibration control based on velocity feedback algorithms is realized. The results show that the predicted strain without considering the piezoelectric nonlinearity is 80 % smaller than the finite element structure at 500 V. Meanwhile, the errors of Root Mean Squared (RMS) control displacement without considering the piezoelectric nonlinearity are more than 24 % when vibration amplitudes achieve 10 % of the membrane thickness. The developed model provides theoretical implications for active vibration control of flexible structures with piezoelectric actuators in strong electric field environments. • Active vibration control of membrane structures is achieved by using piezoelectric actuators. • The actuation equation for strong electric field nonlinearity is derived by incorporating the piezoelectric nonlinear constitutive equation. • Considering piezoelectric nonlinearity under strong electric fields leads to improved control performance in controlling large amplitude vibrations. • Utilizing an axial force control strategy significantly enhances the control performance of flexible structures when dealing with large amplitude vibrations. [ABSTRACT FROM AUTHOR]

Highlights: [•] Nd doped can improve the antiferroelectric stability of PLZST ceramics. [•] With the increase of Nd content, the strain of the ceramics enhanced. [•] The largest electric field-induced strain of 0.63% was obtained. [•] Large strain is beneficial for the development of transducers/actuators. [ABSTRACT FROM AUTHOR]