Fabricating AC/DC nanogenerators based on single ZnO nanowires by using a nanomanipulator in a scanning electron microscope

Single zinc oxide nanowires(ZnO NWs)are promising for nanogenerators because of their excellent semiconducting and piezoelectric properties,but characterizing the latter efficiently is challenging.As reported here,an electrical breakdown strategy was used to construct single ZnO NWs with a specific length.With the high operability of a nanomanipulator in a scanning electron microscope,ZnO-NW-based twoprobe and three-probe structures were constructed for fabricating AC/DC nanogenerators,respectively.For a ZnO NW,an AC output of between−15.31 mV and 5.82 mV was achieved,while for a DC nanogenerator,an output of24.3 mV was realized.Also,the three-probe structure’s output method was changed to verify the distribution of piezoelectric charges when a single ZnO NW is bent by a probe,and DC outputs of different amplitudes were achieved.This study provides a low-cost,highly convenient,and operational method for studying the AC/DC output characteristics of single NWs,which is beneficial for the further development of nanogenerators.

Dielectric and piezoelectric properties of(Li,Ce) modified NaBi_5Ti_5O_(18) composite ceramics

Nominal （Li0.5Ce0.5）x（Na0.5Bi0.5）（1-x）Na0.5Bi4.5Ti5O18 composite ceramics were fabricated using conventional solid-state reaction method. The coexistence of bismuth layer-structured phase and perovskite phase was determined in these ceramics using XRD technique. At room temperature, the x=0.11 sample showed the largest piezoelectric constant, d33, of about 26.5 pC/N and the largest electromechanical coupling factor, kt, of about 30%. Even after annealing at 500 ℃, the value of d33 was still about 19 pC/N, in x=0.08-0.11 samples. Moreover these composite ceramics showed low temperature coefficients of dielectric constant and high electrical resistivity in the temperature region of 450-550 ℃. These results indicated that （Li, Ce） modified NaBi5Ti5O18 composite ceramics were promising piezoelectric materials for high-temperature applications.

Effects of Cr_2O_3 doping on the electrical properties and the temperature stabilities of PZT binary piezoelectric ceramics

The ceramics with Pb1.04Zr0.52Ti0.48O3 ＋ z wt.% Cr2O3 were prepared using the traditional technique. The effects of Cr2O3 doping on the phase structure, the microstructure, and the electrical properties of ceramics were investigated. Meanwhile, the temperature stabilities of the resonant frequency （fx） were studied. The results showed that the △fr/fr,25℃ decreased with the addition of 0.2 wt.% - 0.8 wt.% Cr2O3 as compared with the undoped samples. The minimum value （-0.182%） of △fr/fr,25℃ was obtained for z = 0.6 wt.% Cr2O3 samples that sintered at 1260℃. The values of ε^τ33/ε0 = 1650, tanδ = 0.006, d33 = 328 pC/N, Kp = 0.63, Qm = 2300 were obtained when Cr2O3 was 0.6 wt.%, which exhibited more excellent piezoelectric properties than other compositions such as those with z = 0.2 wt.%, 0.4 wt.%, and 0.8 wt.%, but had a similar value as compared with the tmdoped samples. When the Cr2O3 additive increased, the Curie temperature moved toward low temperature and the changes of resonant frequency changed from positive to negative with increasing temperature.

Preparation and Piezoelectric Properties of CuO-added(Ag_(0.75)Li_(0.1)Na_(0.1)K_(0.05_)NbO_3 Lead-free Ceramics

CuO-doped（Ag0.75Li0.1Na0.1K0.05）NbO3（ALNKN-xCuO, x = 0.2mol%） lead-free piezoelectric ceramics were prepared by the solid-state reaction method in air atmosphere. The effects of CuO addition on the phase structure, microstructure, and piezoelectric properties of the ceramics were investigated. The experimental results show that the ALNKN ceramics without doping CuO possess rhombohedral phase along with K2NbrO16- type phase and metallic silver phase. For all of the CuO-doped ALNKN ceramics, a pure perovskite structure with the orthorhombic phase was obtained by enclosing the samples in a corundum tube. A homogeneous microstructure with＇the grain size of about 1 ~tm was formed for the ceramics with 0.5mo1% CuO. The grain size increases with increasing amount of CuO. The temperature dependence of dielectric properties indicates that the ferroelectric phase of the ALNKN-xCuO ceramics becomes less stable with the addition of CuO. The ceramics with x = lm01% exhibit relatively good electrical properties along with a high Curie temperature. These results will provide a helpful guidance to preparing other AN-based ceramics by solid-state reaction method in air atmosphere.

Effect of Li content on the microstructure and properties of lead-free piezoelectric(K_(0.5)Na_(0.5))_(1-x)Li_xNbO_3 ceramics prepared by SPS

Lead-free piezoelectric （K0.5sNa0.5）1-xLixNbO3 （x = 0at%-20at%） ceramics were synthesized by spark plasma sintering （SPS） at low temperature and the effects of LiNbO3 addition on its crystal structure and properties were also studied. When the Li content was less than 6at%, a single proveskite phase with the similar structure of （K0.5Na0.5）NbO3 was formed; and a secondary phase with K3Li2Nb5O15 structure was observed in the 6at% 〈 x 〈 20at% compositional range. Furthermore, LiNbO3 existed as the third phase when the Li content was higher than 8at%. The grain sizes increased from 200-500 nm to 5-8 μm when the K3Li2Nb5O15 and LiNbO3 like phases were formed. With increasing Li content, the relative density of the ceramics first decreased from 97% to 93% and then kept constant. The piezoelectric coefficient d33, dielectric constant, and planner electromechanical coupling factor exhibited a decreasing tendency with increasing Li content because of the decrease in density and the formation of the secondary phase such as K3Li2Nb5O15 and LiNbO3. The formation of dense microstructure with a single phase is necessary in improving the properties of the （K0.5Na0.5）1-xLixNbO3 ceramics.

Dielectric and Piezoelectric Properties of 0-3 PZT/PVDF Composite Doped with Polyaniline

Lead zirconate titanate （ PZT ） / polyvinylidene fluoride （PVDF） 0-3 piezoelectric composites doped with polyaniline （PANI） were obtained by hot-press method. The polarization properties of the composites were characterized by XRD and P- E hysteresis loops at room temperature. And the dielectric and piezoelectric properties were also measured. The results show that the poling of PZT could be effectively carried oat and the dielectric constant e, and dissipation tanδ increase monatonously by increasing the volume fraction of PANI in the composite. The piezoelectric constant d33, and the planar electromechanical coupling factor kp increase while the mechanical quality factor Qm decreases with the increase in the content of PANI. The d33, kp and Qm show the extremum values at 8 vol%-10 vol% PANI.

Piezoelectric properties of low loss and high Curie temperature (Bi, La)FeO_3-Pb(Ti, Mn)O_3 ceramics with Mn doping

Piezoelectric ceramics of 0.6(Bi0.9La0.1)FeO3-0.4Pb(Ti1-xMnx)O3 (BLF-PTM) for x=0, 0.01, 0.02, and 0.03 were prepared by sol-gel process combined with a solid-state reaction method. The tan? for BLF-PTM of x=0.01 is just 0.006 at 1 kHz, drastically decreasing by using Mn dopants. The TC increases to 490 ℃ for BLF-PTM of x=0.02. Furthermore, Mn modification effectively enhances the poling state and the piezoelectric properties of BLF-PTM. The kp, Qm, d33, and g33 of 0.34, 403, and 124 pC1·N-1 and 37×10-3 Vm·N-1 are achieved for BLF-PTM of x=0.01. The results indicate that Mn modified BLF-PTM is a competitive high power and high temperature piezoelectric material with excellent piezoelectric properties.

Effects of CeO_2 doping on the structure and properties of PSN-PZN-PMS-PZT piezoelectric ceramics

Quinary system piezoelectric ceramics PSN-PZN-PMS-PZT were prepared by using a two-step method. The effects of CeO2 doping on piezoelectric and dielectric properties of the system were investigated at morphotropic phase boundary （MPB）. The results reveal that the relative dielectric constant ε33^T｜ε0, the Curie temperature To, the piezoelectric constant d33, the mechanical quality factor Qm, and the electromechanical coupling coefficient Kp are changed with the increase of CeO2 content. On the other hand, the effects of CeO2 doping on the dielectric properties of PSN-PZN-PMS-PZT piezoelectric ceramics at high electric field are consistent with the change at weak electric field. The values of dielectric constant and dielectric loss are enhanced with the increasing of electric field.

Microstructure and electrical properties of Ti-modified (Na_(0.5)K_(0.5))(Ti_xNb_(1-x))O_3 lead-free piezoelectric ceramics

Ti-Modified (Na0.5K0.5)(TixNb1-x)O3 (NKNT) piezoelectric ceramics were fabricated by double-layer buried powder process at 1020°C for 2 h. The microstructures,and piezoelectric and dielectric properties of the lead-free NKNT ceramics were investigated. X-ray diffraction re-sults indicated that Ti4+ had diffused into the (Na0.5K0.5)NbO3 lattices to form a solid solution with a perovskite structure. The introducing of Ti into the (Na0.5K0.5)NbO3 solid solution effectively reduced the sintering temperature and...

Piezoelectric and dielectric properties of Cr-doped PSN-PZN-PZT qua-ternary piezoelectric ceramics

PSN-PZN-PZT + x wt. %Cr2O3, X = 0.0-0-9, were prepared by conventional mixed oxide techniques at sintering temperatures of 1220 degrees C-1300 degrees C for 2 h. The effect of sintering temperature on the microstructure and the piezoelectric properties was investigated by XRD, SEM, and other conventional measurement. The result indicated that with temperature increasing, the valence of Cr ion from Cr5+ or Cr6+ changes into C3+, and the piezoelectric properties turn hard. With increasing Cr2O3 content, the amount of rhombohedral phases increases and the morphotropic boundary phase is correspondingly shifts to rhombohedral phase. A uniform microstructure and excellent comprehensive properties were obtained at 1240 degrees C as the amount of Cr2O3 is 0.5 wt.%.

Electronic,Elastic and Piezoelectric Properties of Two-Dimensional Group-Ⅳ Buckled Monolayers

Electronic, elastic and piezoelectric properties of two-dimensional （2D） group-IV buckled monolayers （GeSi, SnSi and SnGe） are studied by first principle calculations. According to our calculations, SnSi and SnGe are good 2D piezoelectric materials with large piezoelectric coefficients. The values of d11d11 of SnSi and SnGe are 5.04pm/V and 5.42pm/V, respectively, which are much larger than 2D MoS2 （3.6pm/V） and are comparable with some frequently used bulk materials （e.g., wurtzite AlN 5.1pm/V）. Charge transfer is calculated by the L wdin analysis and we find that the piezoelectric coefficients （d11d11 and d31） are highly dependent on the polarizabilities of the anions and cations in group-IV monolayers.

Effects of Excess Barium on the Structure and Electrical Properties of(Ba,Ca)TiO_3 Piezoelectric Ceramics with High Mechanical Quality Factors

Manganese-doped Ba（0.925）Ca（0.075）TiO3 lead-free piezoelectric ceramics（abbreviated as BCT）with high mechanical quality factor were synthesized by conventional solid-state reaction method.The effects of excess Ba on the crystal structure,microstructure,and electrical properties of the ceramics were systematically investigated.X-ray diffraction and Raman spectra revealed that Ca^2＋ions were pushed from Ba sites to Ti sites of BCT when 1.5 mol%extra Ba^2＋ions were added after sintering.The grain size of the ceramics was decreased by adding extra Ba^2＋ions.The mechanical quality factor and resistivity of the ceramics decreased dramatically when the excess Ba was more than 1.5 mol%.High piezoelectric coefficients（d（33）=150-190 pC/N）and high mechanical quality factors（Qm=1 000-1 200）were obtained in the ceramics when the excess of Ba was between 0.5 mol%and 1 mol%.These results indicated that the properties of BCT ceramics could be tailored by adjusting the content of Ba.

Size-dependent electromechanical properties in piezoelectric superlattices due to flexoelectric effect

Piezoelectric superlattice is a potential component for nanoelectromechanical systems. Due to the strong nonlocal effect such as flexoelectric effect at interfaces, classical piezoelectric theory is unable to accurately describe the electromechanical response of piezoelectric superlattice at nanoscale scale. Based on the previous nonlocal thermodynamics theory with flexoelectric effect Liu et al. （2016）, the size- dependent electromechanical properties of piezoelectric superlattices made of BaTiO3 （BTO） and PbTiO3 （PRO） layers are investigated systematically in the present work. Giant strain gradient is found near the interface between BTO and PTO layers, which leads to the significant enhancement of polarization in the superlattice due to the flexoelectric effect. For the piezoelectric BTO-PTO superlattices with different unit- cell sizes, the thickness of interface with nontrivial strain gradient is almost constant. The influence of strain gradient at the interface becomes significant when the size of superlattice decreases, As a result, a strong size dependence of electromechanical properties is predicted for the piezoelectric BTO-PTO superlattices, In particular, for the superlattices with a specific thickness ratio of BTO and PTO layers, the piezoelectric response can be several times larger than that of bulk structure. The present work demonstrates a practical wast to design the piezoelectric superlattices with high piezoelectric coefficient by using the nonlocal effect at nanoscale.

Microstructures and Electrical Properties of Bi_(0.5)-(Na_(1-x-y)K_xLi_y)_(0.5)TiO_3 Lead-free Piezoelectric Ceramics

The microstructures and electrical properties of Bi0.5（Na1-x-yKxLiy）0.5TiO3 lead-free piezoelectric ceramics were studied.These ceramics were prepared by conventional ceramic technique.XRD analysis reveals that the ceramics possess almost pure perovskite phase when y≤0.2.The SEM results show that,with more amounts of Li＋,the crystalline grain growing speed is accelerated,and the sintering temperature can effectively be decreased.The measurements of piezoelectric properties indicate that the ceramics with relatively low amount of Li＋ and high amount of K＋ have comparatively large piezoelectricity.The dielectric measurements show that the ceramics have properties like relaxor ferroelectrics and diffuse phase transition（DPT） at Td and Tc,respectively.The results of ferroelectric measurements reveal the system has relatively higher remanent polarization Pr（27.6 μC/cm2） and lower coercive field Ec（37.5 kV/cm）.

Dielectric and piezoelectric properties of(110) oriented Pb(Zr_(1-x)Ti_x)O_3 thin films

A phenomenological Landau–Devonshire theory is developed to investigate the ferroelectric, dielectric, and piezoelectric properties of（110） oriented Pb（Zr_（1-x）Ti_x）O_3（x = 0.4, 0.5, 0.6, and 0.7） thin films. At room temperature, the tetragonal a_1 phase, the orthorhombic a_2c phase, the triclinic γ_1 phase, and the triclinic γ_2 phase are stable. The appearance of the negative polarization component P_2 in the a_2c phase and the γ_1 phase is attributed to the nonlinear coupling terms in the thermodynamic potential. The γ phase of the Pb（Zr_（1-x）Ti_x）O_3 thin films has better dielectric and piezoelectric properties than the a_2c phase and the a_1 phase. The largest dielectric and piezoelectric coefficients are obtained in the Pb（Zr_（0.5）Ti_（0.5））O_3 thin film. The piezoelectric coefficient of 110–150 pm/V is obtained in the（110） oriented Pb（Zr_（0.5）Ti_（0.5））O_3 thin film, and the Pb（Zr_（0.3）Ti_（0.7））O_3 thin film has the remnant polarization and relative dielectric constant of 50 μC/cm^2 and 100, respectively,which are in agreement with the experimental measurements reported in the literature.

Piezoelectric and electro optic properties of tetragonal(1-x)Pb(Mg_(1/3)Nb_(2/3))O_3-xPbTiO_3 single crystals by phenomenological theory

An eighth-order Landau–Devonshire theory is constructed to investigate the piezoelectric and electro–optic properties of tetragonal（1- x）Pb（Mg1/3Nb2/3）O3–xPbTiO3 single crystals（x = 0.38 and x = 0.4）. The dielectric stiffness coefficients of the Landau potential are obtained by fitting to the dielectric properties and the phase transition temperature between cubic phase and tetragonal phase. It is indicated that tetragonal（1- x）Pb（Mg1/3Nb2/3）O3–xPbTiO3 single crystals have the firstorder cubic-tetragonal phase transitions. The dielectric constants are in great agreement with the experimental results.The piezoelectric coefficients d33 and d31at room temperature are about 145 p C/N and-62 p C/N respectively which are smaller than that of（1- x）Pb（Mg1/3Nb2/3）O3–xPbTiO3 single crystals around the morphotropic phase boundary.Moreover, tetragonal（1- x）Pb（Mg1/3Nb2/3）O3–xPbTiO3 single crystals have the linear electro–optic coefficients rc =33.7 pm/V and rc = 28.8 pm/V for x = 0.38 and x = 0.4, respectively which are in accordance with the measurements.

Intrinsic Orientation Effect on the Piezoelectric Response of Multi-domain 0.26Pb(In1/2Nb1/2)O3–0.46Pb(Mg1/3Nb2/3)O3–0.28PbTiO3 Crystals

The crystal intrinsic orientation effect on the piezoelectric response of multi-domain 0.26Pb（Inl/2Nbm）O3-0.46Pb（Mg1/3Nb2/3）O3-0.28PbTiO3 （PIN-PMN-0.28PT） crystals was investigated by coordinate transformation method. The results indicate that crystal intrinsic orientation effect plays a crucial role in determining the piezoelectric properties of multi-domain crystals. Almost 58% and 69% of the transverse piezoelectric coefficients d31 and d32, respectively, and 67% longitudinal piezoelectric coefficient d33 of multi- domain PIN-PMN-0.28PT crystals poled along [011 ]c originate from crystal intrinsic orientation effect. For [001 ]c poled multi-domain PIN-PMN-0.28PT crystals, intrinsic orientation effect contributes to the transverse and longitudinal piezoelectric coefficient at least 79% and 74%, respectively.

Pick-up strategies for and electrical characterization of ZnO nanowires with a SEM-based nanomanipulator

Because of their unique mechanical and electrical properties,zinc oxide(ZnO)nanowires are used widely in microscopic and nanoscopic devices and structures,but characterizing them remains challenging.In this paper,two pick-up strategies are proposed for characterizing the electrical properties of ZnO nanowires using SEM equipped with a nanomanipulator.To pick up nanowires efficiently,direct sampling is compared with electrification fusing,and experiments show that direct sampling is more stable while electrification fusing is more efficient.ZnO nanowires have cut-off properties,and good Schottky contact with the tungsten probes was established.In piezoelectric experiments,the maximum piezoelectric voltage generated by an individual ZnO nanowire was 0.07 V,and its impedance decreased with increasing input signal frequency until it became stable.This work offers a technical reference for the pick-up and construction of nanomaterials and nanogeneration technology.

Effects of Conductive Carbon Black on Thermal and Electrical Properties of Barium Titanate/Polyvinylidene Fluoride Composites for Road Application

In the field of roads,due to the effect of vehicle loads,piezoelectric materials under the road surface can convert mechanical vibration into electrical energy,which can be further used in road facilities such as traffic signals and street lamps.The barium titanate/polyvinylidene fluoride(BaTiO_(3)/PVDF)composite,the most common hybrid ceramic-polymer system,was widely used in various fields because the composite combines the good dielectric property of ceramic materials with the good flexibility of PVDF material.Previous studies have found that conductive particles can further improve the dielectric and piezoelectric properties of other composites.However,few studies have investigated the effect of conductive carbon black on the dielectric and piezoelectric properties of BaTiO_(3)/PVDF composites.In this study,BaTiO_(3)/PVDF/conductive carbon black composites were prepared with various conductive carbon black contents based on the optimum ratio of BaTiO_(3)to PVDF.The effects of conductive carbon black content on the morphologies,thermal performance,conductivities,dielectric properties,and piezoelectric properties of the BaTiO_(3)/PVDF/conductive carbon black composites were then investigated.The addition of conductive carbon black greatly enhances the conductivities,dielectric properties,and piezoelectric properties of the BaTiO_(3)/PVDF/conductive carbon black composites,especially when the carbon black content is 0.8%by weight of PVDF.Additionally,the conductive carbon black does not have an obvious effect on the morphologies and thermal stabilities of BaTiO_(3)/PVDF/conductive carbon black composites.