Effective property of piezoelectric composites containing coated nano-elliptical fibers with interfacial debonding

Based on both the spring layer interface model and the Gurtin-Murdoch surface/interface model,the anti-plane shear problem is studied for piezoelectric composites containing coated nano-elliptical fibers with imperfect interfaces.By using the complex function method and the technique of conformal mapping,the exact solutions of the electroelastic fields in fiber,coating,and matrix of piezoelectric nanocomposites are derived under far-field anti-plane mechanical and in-plane electrical loads.Furthermore,the generalized self-consistent method is used to accurately predict the effective electroelastic moduli of the piezoelectric nanocomposites containing coated nano-elliptical fibers with imperfect interfaces.Numerical examples are illustrated to show the effects of the material constants of the imperfect interface layers,the aspect ratio of the fiber section,and the fiber volume fraction on the effective electroelastic moduli of the piezoelectric nanocomposites.The results indicate that the effective electroelastic moduli of the piezoelectric nanocomposites can be significantly reduced by the interfacial debonding,but it can be improved by the surface/interface stresses at the small scale,which provides important theoretical reference for the design and optimization of piezoelectric nanodevices and nanostructures.

Effects of Sr^(2+) substitution on the structural, dielectric, and piezoelectric properties of PZT-PMN ceramics

This study described the structural, dielectric, and piezoelectric behavior of Pb1-xSrx[（Zr0.52Ti0.48）0.95（Mn1/3Nb2/3）0.05]O3 ceramics （PSZT-PMN, x=0, 0.025, 0.050, and 0.075）, prepared by a semi-wet route. X-ray diffraction, dielectric, and piezoelectric investigations were carried out to analyze the crystal structure. The relative dielectric constant and dielectric loss were both calculated as the functions of temperature. The room-temperature dielectric constant reaches a maximum for a Sr2＋-modified PZT-PMN ceramic with an x value of 0.050, which corresponds to the morphotropic phase boundary （MPB）. Raman spectroscopy studies also confirm the existence of this MPB for x=0.050. The piezoelectric strain coefficients （d33） value shows a maximum response for this composition. In addition, the phase transition temperature decreases significantly when the Sr2＋concentration increases in the PZT-PMN ceramics.

Theoretical study on dynamic effective electroelastic properties of random piezoelectric composites with aligned inhomogeneities

The closed-form solutions of the dynamic problem of heterogeneous piezoelectric materials are formulated by introducing polarizations into a reference medium and using the generalized reciprocity theorem.These solutions can be reduced to the ones of an elastodynamic problem.Based on the effective medium method,these closedform solutions can be used to establish the self-consistent equations about the frequencydependent effective parameters,which can be numerically solved by iteration.Theoretical predictions are compared with the experimental results,and good agreement can be found.Furthermore,the analyses on the effects of microstructure and wavelength on the effective properties,resonance frequencies,and attenuation are also presented,which may provide some guidance for the microstructure design and analysis of piezoelectric composites.

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.

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.

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.

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 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.

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.

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.

Piezoelectric and dielectric properties of Li_x(K_(0.46)Na_(0.54))_(1-x)Nb_(0.86)Ta_(0.1)Sb_(0.04)O_3 lead-free ceramics

Lead-free piezoelectric ceramics Lix(K0.46Na0.54)1-xNb0.86Ta0.1Sb0.04O3 (with x ranging from 0 to 0.1) were synthesized by conventional solid state sintering method. The effect of cationic substitution of Li for K and Na in the A sites of perovskite lattice on the structure, phase transition behavior and electrical properties were investigated. Morphotropic phase boundaries(MPB) between orthorhombic and tetragonal phase are found in the composition range of 0.06≤x≤0.08. Analogous to Pb(Zr,Ti)O3, the dielectric and piezoelectric properties are enhanced for the composition near the morphotropic phase boundary. The Li0.06(K0.46Na0.54)0.94- Nb0.86Ta0.1Sb0.04O3 ceramics show excellent electrical properties, that is, piezoelectric constant d33=215 pC/N, planar electromechanical coupling factor kp=41%, dielectric constant ε 3T3 /ε0=1 303, and dielectric loss tan δ=2.45%. The results indicate that Lix(K0.46Na0.54)1-x Nb0.86 Ta0.1Sb0.04O3 ceramic is a promising lead-free piezoelectric material.

Dielectric, piezoelectric, and ferroelectric properties of lanthanum-modified PZTFN ceramics

Specimens of Pb1-1.5xLax（Zr0.53 Ti0.47）1-y-zFeyNb2O3 （x = 0, 0.004, 0.008, 0.012, and 0.016, y = z = 0.01） （PZTFN） ceramics were synthesized by a semi-wet route. In the present study, the effect of La doping was investigated on the structural, microstructural, dielectric, piezoelectric, and ferroelectric properties of the ceramics. The results show that, the tetragonal （space group P4mm） and rhombohedral （space group R3c） phases are observed to coexist in the sample at x = 0.012. Microstructural investigations of all the samples reveal that La doping inhibits grain growth. Doping of La into PZTFN improves the dielectric, ferroelectric, and piezoelectric properties of the ceramics. The hys- teresis loops of all specimens exhibit nonlinear behavior. The dielectric, piezoelectric and ferroelectric properties show a maximum response atx 〉 0.012, which corresponds to the morphotropic phase boundary （MPB）.

Dielectric behaviors at microwave frequencies and Mossbauer effects of chalcedony, agate, and zultanite

In this study, dielectric properties within 8-12 GHz microwave frequencies, inductively coupled plasma-atomic emis- sion spectrometry, Fourier transform infrared spectrometry, synchronized two thermal analyses, and 57Fe Mossbauer spectroscopy analysis of chalcedony, agate, and zultanite samples from Turkey are presented. Agate and chalcedony show the same nine vibrational absorption peaks obtained unlike zultanite from FTIR spectra in the 350 cm-1 to 4000 cm-1 range, ε＇ values of chalcedony, agate and zultanite derived at 10.5 GHz were 4.67, 4.41, and 7.34, respectively, eI and e~ values of the studied samples at the microwave frequencies are related to the percentage weight of their constituent parts in their chemical compositions. 57Fe Mossbauer spectroscopy results confirm the existence of iron-containing islands in the crystal structure of zultanite, agate, and chalcedony samples, equipped them with magnetic features typical for magnetic nanoparticles including superparamagnetism. The presence of iron-containing islands significantly affects the magnetic, dielectric, and optical properties of studied samples that are not observed for pure minerals without any foreign inclusions.

Effect of Nano Silver Modification on the Dielectric Properties of Ag@TiO_(2)/PVDF Composites

To get a dielectric material with a high dielectric permittivity and suppressed dielectric loss,nano-Ag with a particle size of 20 nm and Ag@TiO_(2)core-shell particles with diameters of approximately 70-120 nm were embedded in polyvinylidene fluoride(PVDF)to fabricate nano-Ag/Ag@TiO_(2)/PVDF composites.After being modified by nano-Ag with 3 vol%optimal amount,the relative permittivity(ε_r)at 100 Hz of 50 vol%Ag@TiO_(2)/PVDF composites was 61,and the dielectric loss can be suppressed to 0.04,almost 96.4%lower than that of unmodified composites,and a higher frequency stability of bothε_r and loss has also been found.The underlying mechanism of the reduced loss was attributed to Maxwell-Wagner polarization and the Coulomb blockade effect caused by the introduction of a small amount of nano-Ag,which will block the movement of electrons between metal nanoparticles and composites.The space charge polarization and conductance loss are weakened at lower and higher Ag@TiO_(2)filling ratios,respectively,thus leading to a very low loss of the composites.

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.

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...

真空热压烧结铌酸锂压电陶瓷研究

采用真空热压烧结法对铌酸锂粉体进行烧结制备铌酸锂压电陶瓷,通过改变烧结温度、保温时间来确定最佳烧结方案;对烧结样品的密度、显微结构、物相组成、压电和介电等性能进行了测试。研究表明:在烧结温度900℃、保温时间120 min、压力35 MPa条件下制备的铌酸锂压电陶瓷致密度最高(4.62 g/cm^(3)),同时其压电常数d_(33)达最大(8.7 pC/N),相较于传统固相烧结法及CO_(2)激光烧结法,其压电常数分别提高7.9 pC/N和2.7 pC/N。当测试频率介于1 kHz~1 MHz时,不同制备条件下铌酸锂压电陶瓷的介电常数均呈现迅速下降后趋于稳定的趋势。

不同纤维增强对PZT/PVA复合材料性能影响的研究

压电陶瓷复合材料较低的力学性能限制其应用。为进一度探究纤维种类及掺量对锆钛酸铅(PZT)/聚乙烯醇(PVA)复合材料性能影响规律,对不同纤维掺量下碳纤维/PZT/PVA、芳纶纤维/PZT/PVA复合材料开展电学及力学性能测试,分析纤维种类、掺量及PZT/PVA体积比对试件介电、压电性能及弯曲、拉伸性能的影响规律,并结合电镜扫描(SEM)分析纤维掺量对试件性能的影响。结果表明,少量的纤维掺量能够提高复合材料的电学性能,过量的纤维使得复合材料结构孔隙结构增加,介质常数和压电常数均减小,介质损耗增大。7%芳纶纤维/0.5PZT/0.5PVA、5%芳纶纤维/0.6PZT/0.4PVA、3%芳纶纤维/0.7PZT/0.3PVA复合材料的介电性能和压电性能较高。芳纶纤维掺量为9%时,芳纶纤维/0.5PZT/0.5PVA、芳纶纤维/0.6PZT/0.4PVA、芳纶纤维/0.7PZT/0.3PVA、芳纶纤维/0.8PZT/0.2PVA复合材料的弯曲强度分别提高了10.72%、14.49%、13.85%及16.78%,拉伸强度分别提高了24.04%、23.94%、27.00%和28.52%。纤维在试件内部形成网状结构从而提升试件力学性能,且由于芳纶纤维不导电,因此可以在复合材料中加入芳纶纤维的数量比碳纤维多,其力学性能也会大大提高。

光固化3D打印制备高性能BaTiO_(3)压电陶瓷

光固化3D打印技术在制备异形压电陶瓷方面具有广阔的应用前景。本文采用数字光处理技术制备了钛酸钡(BaTiO3)压电陶瓷,研究了坯体形貌、烧结温度对钛酸钡微观结构的影响。结果表明,曲拉通X-100的引入使陶瓷料浆的黏度小于3 Pa·s,同时陶瓷粉体的引入未改变树脂的性质。陶瓷坯体层间结合良好,且无明显缺陷。烧成后的BaTiO_(3)陶瓷内部含有四方与正交两种晶相,剩余极化强度为27.6μC/cm^(2),矫顽场为4.6 kV/cm,相对介电常数为2512,介电损耗为0.0091,居里温度为167℃,介电常数为182 pC/N。

BF-PT-BZT三元系高温压电陶瓷的介电压电温度稳定性

采用传统固相反应法制备0.54BiFeO_(3)-0.33PbTiO_(3)-0.13Ba(Zr_(x)Ti_(1-x))O_(3)(BF-0.33PT-0.13Ba(Zr_(x)Ti_(1-x)),0.4≤x≤0.8)三元系压电陶瓷,研究了Zr含量(x)对陶瓷的微观结构以及介电、铁电和压电性能的影响。X线衍射(XRD)结果表明,BF-0.33PT-0.13Ba(Zr_(x)Ti_(1-x))三元系陶瓷为单一钙钛矿结构,当0.4≤x≤0.7时,陶瓷相结构为三方-四方相共存;当x=0.8时,陶瓷为三方相结构。扫描电子显微镜(SEM)结果表明,随着Zr含量的增加,陶瓷晶粒尺寸逐渐增加。在25~400℃时,陶瓷的压电常数d 33的波动小于±6%。当x=0.7时,BF-0.33PT-0.13Ba(Zr_(x)Ti_(1-x))具有最优异的综合性能,其介电常数εr、居里温度T_(C)、压电常数d_(33)分别为1194(1 kHz)、438℃和330 pC/N,在25~300℃时,陶瓷的电容温度系数和压电常数变化率分别为16%和8%。结果表明,BF-0.33PT-0.13Ba(Zr_(0.7)Ti_(0.3))陶瓷在高温压电器件中具有较广的应用前景。