Enhanced piezoelectric properties and depolarization temperature in textured(Bi_(0.5)Na_(0.5))TiO_(3)-based ceramics via homoepitaxial templated grain growth

Enhanced piezoelectric response was usually achieved in(Bi_(0.5) Na_(0.5))TiO_(3)(BNT)-based ceramics with sacrifice of depolarization temperature T_(d),seriously limiting their usage range in electromechanical applications.In this work,we propose to explore piezoelectric anisotropy and domain engineering in composition&microstructure-controlled textured ceramics to resolve this issue.[001]c-textured 0.94(Bi_(0.5) Na_(0.5))TiO_(3)–0.06BaTiO_(3)(0.94BNT-0.06BT)ceramics with Lotgering factor F_(001)-91%were fabricated through homoepitaxial templated grain growth(TGG)via using 0.94BNT-0.06BT microplatelet templates.The textured samples exhibited more ordered domains with facilitated domain switching behavior,being consistent with saturated high polarization achieved at lower electric fields.Increasing F_(001) to above 60%enables rapid enhancement of piezoelectric response.Notably,compared to non-textured counterpart,the maximally textured ceramics exhibited-236%enhanced piezoelectric coefficient(d_(33)-302 pC/N)and-280%enhanced piezoelectric voltage coefficient(g_(33)-49.8×10^(−3)Vm/N),together with slightly increased depolarization temperature(T_(d)-106℃).Moreover,those values are approaching or even higher than the single-crystal values.This work not only provides important guidelines for design and synthesis of novel textured ceramics with improved comprehensive electrical properties,but also can expand application fields of BNT-based ceramics.

Physics-embedded machine learning search for Sm-doped PMN-PT piezoelectric ceramics with high performance

Pb(Mg_(1/3)Nb_(2/3))O_(3)–PbTiO_(3)(PMN-PT)piezoelectric ceramics have excellent piezoelectric properties and are used in a wide range of applications.Adjusting the solid solution ratios of PMN/PT and different concentrations of elemental doping are the main methods to modulate their piezoelectric coefficients.The combination of these controllable conditions leads to an exponential increase of possible compositions in ceramics,which makes it not easy to extend the sample data by additional experimental or theoretical calculations.In this paper,a physics-embedded machine learning method is proposed to overcome the difficulties in obtaining piezoelectric coefficients and Curie temperatures of Sm-doped PMN-PT ceramics with different components.In contrast to all-data-driven model,physics-embedded machine learning is able to learn nonlinear variation rules based on small datasets through potential correlation between ferroelectric properties.Based on the model outputs,the positions of morphotropic phase boundary(MPB)with different Sm doping amounts are explored.We also find the components with the best piezoelectric property and comprehensive performance.Moreover,we set up a database according to the obtained results,through which we can quickly find the optimal components of Sm-doped PMN-PT ceramics according to our specific needs.

A Hybrid Compensation Scheme for the Input Rate-Dependent Hysteresis of the Piezoelectric Ceramic Actuators

A hybrid compensation scheme for piezoelectric ceramic actuators(PEAs)is proposed.In the hybrid compensation scheme,the input rate-dependent hysteresis characteristics of the PEAs are compensated.The feedforward controller is a novel input rate-dependent neural network hysteresis inverse model,while the feedback controller is a proportion integration differentiation(PID)controller.In the proposed inverse model,an input ratedependent auxiliary inverse operator(RAIO)and output of the hysteresis construct the expanded input space(EIS)of the inverse model which transforms the hysteresis inverse with multi-valued mapping into single-valued mapping,and the wiping-out,rate-dependent and continuous properties of the RAIO are analyzed in theories.Based on the EIS method,a hysteresis neural network inverse model,namely the dynamic back propagation neural network(DBPNN)model,is established.Moreover,a hybrid compensation scheme for the PEAs is designed to compensate for the hysteresis.Finally,the proposed method,the conventional PID controller and the hybrid controller with the modified input rate-dependent Prandtl-Ishlinskii(MRPI)model are all applied in the experimental platform.Experimental results show that the proposed method has obvious superiorities in the performance of the system.

Research of Lead-free Na_(0.5)Bi_(0.5)TiO_(3)-BaTiO_(3)System Piezoelectric Ceramics

To reduce the coercive field of Na_(0.5)Bi_(0.5)TiO_(3),Ba TiO_(3)were added as dopant materials.Then the(1-x)Na_(0.5)Bi_(0.5)TiO_(3)-xBaTiO_(3)ceramic samples were produced in solid synthetic way.The optimum preparation condition and piezoelectric properties of the samples were investigated.The XRD results show that the fabric transites from rhombohedral to tetragonal gradually with the substitution of the Ba^(2+).The morphotropic phase boundaries(MPB)exists in the composition range of 0.06.

A New Capillary Electrophoresis Apparatus with Piezoelectric Ceramics High Voltage Source and Amperometric Detector

A new capillary electrophoresis apparatus was designed. Piezoelectric ceramics transformer technology was first applied in capillary electrophoresis, a high voltage and stable source was made. Amperometric detector was used in which the working electrode was closely opposite to the end of capillary. The apparatus was characterized in good reproducibility, safety and very low cost.

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.

Influence of Sb_2O_3 doping on the properties of KBT-NBT-BT lead-free piezoelectric ceramics

0.144（K0.5Bi0.5）TiO3-0.85（Na0.5Bi0.5）TiO3-0.006BaTiO3（KBT-NBT-BT） lead-free piezoelectric ceramics were prepared using a conventional solid state method.The influence of Sb2O3 doping on the crystal phase,surface microstructure and properties of the KBT-NBT-BT lead-free piezoelectric ceramics were investigated using X-ray diffraction（XRD）,scanning electron microscope（SEM） and other analytical methods.The results show that all compositions are of pure perovskite structure solid states.Sb2O3 doping does not influence the microstructure of KBT-NBT-BT lead-free piezoelectric ceramics obviously in the Sb2O3 doping range of 0.1-0.5 wt.%.Sb2O3 functions as a donor when doped small amount,while functions as a acceptor when doped large amount.The piezoelectric strain constant（d33） increases first and then decreases;the dielectric constant（ε33^T/ε0） and the dielectric loss（tanδ） decrease continuously when the amount of Sb2O3 dopant increases.When the doping amount of Sb2O3 is 0.1 wt.%,the KBT-NBT-BT piezoelectric ceramics with good comprehensive properties are obtained,whose d33,ε33^T/ε0 and tanδ are 147 pC/N,1510 and 4.2%,respectively.

Effect of Sintering Time on Structure and Properties in CuO-doping KNN-LS-BF Piezoelectric Ceramics

The 0.6 mol% CuO-doping 0.996(0.95 Na_(0.5)K_(0.5)NbO_3-0.05 LiSbO_3)-0.004 FeBiO_3(KNN-LSBF-CuO) piezoelectric ceramics were synthesized by a solid-state reaction technique, and the structure and piezoelectric properties dependence of sintering time in KNN-LS-BF-CuO ceramics were studied. It is found that all the samples sintered for various time are perovskite structure mixed with orthorhombic symmetry phase and tetragonal phase, but the sintering time has significant influences on the crystalline and properties. When the sintering time increases from 2 hours to 6 hours, the grain of KNN-LS-BF-CuO ceramics becomes more homogeneous and more tight-arrangement. The experimental results reveal that the longer sintering time than 4 hours is beneficial for improving partial properties, such as d_(33), tgδ, and Q_m, but is adverse to ε_r and k_p, the KNNLS-BF-CuO ceramics with optimum properties can be synthesized for 6 hours at 1 060 ℃.

ANALYSIS OF ELECTRIC BOUNDARY CONDITION EFFECTS ON CRACK PROPAGATION IN PIEZOELECTRIC CERAMICS

There are three types of cracks: impermeable crack, permeable crack and conducting crack, with different electric boundary conditions on faces of cracks in piezoelectric ceramics, which poses difficulties in the analysis of piezoelectric fracture problems. In this paper, in contrast to our previous FEM formulation, the numerical analysis is based on the use of exact electric boundary conditions at the crack faces, thus the common assumption of electric impermeability in the FEM analysis is avoided. The crack behavior and elasto-electric fields near a crack tip in a PZT-5 piezoelectric ceramic under mechanical, electrical and coupled mechanical- electrical loads with different electric boundary conditions on crack faces are investigated. It is found that the dielectric medium between the crack faces will reduce the singularity of stress and electric displacement. Furthermore, when the permittivity of the dielectric medium in the crack gap is of the same order as that of the piezoelectric ceramic, the crack becomes a conducting crack, the applied electric field has no effect on the crack propagation.

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.

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.

COMBINED DAMAGE FRACTURE CRITERIA FOR PIEZOELECTRIC CERAMICS

Mechanical and electrical damages are introduced to study the fracture mechanics of piezoelectric ceramics in this paper. Two kinds of piezoelectric fracture criteria are established using the method of least squares combined with a damage analysis of the well-known piezoelectric fracture experiments of Park and Sun’s. One is based on a linear combination of the mechanical and electrical damages and the other on their nonlinear combination. When the combined damage D is up to its critical value Dc, piezoelectric fracture occurs. It is found from the qualitative comparison of the numerical results with the experimental data that the nonlinearly combined damage fracture criterion can give a better prediction of piezoelectric fracture. And it is concluded from the nonlinearly combined damage fracture criterion that a negative electric feld impedes fracture whereas the efect of a positive electric feld on fracture depends on its magnitude.

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.

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.

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.

Phase Structure, Microstructure and Electrical Properties of K_xNa_((1-x))NbO_3 Piezoelectric Ceramics with Different K/Na Ratio

The K_xNa_((1-x))NbO_3(x=0.45, 0.46, 0.47, 0.48, 0.49, 0.50) lead-free piezoelectric ceramics was fabricated by conventional solid-state sintering method. It was found that the ratio of alkaline metal would affect the microstructure, bulk density, and optimum sintering temperatures of ceramics. Meanwhile, the electrical properties were also influenced by modulating the K/Na ratio, exhibiting corresponding composition-dependent properties. The optimum electrical properties of K_xNa_((1-x))NbO_3 such as piezoelectric constant d_(33) = 115 pC/N, mechanical quality factor Q_m = 20, Curie temperature Tc = 365 ~oC, ε_(33)~T/ε_0= 588.1, dielectric loss tan δ = 0.024, bulk density(ρ) = 3.08 g/cm^3, remnant polarization(P_r) = 8.87 μC/cm^2 and coercive field(Ec) = 13.79 kV/cm were obtained at x = 0.46.

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...

CuO added Pb_(0.92)Sr_(0.06)Ba_(0.02)(Mg_(1/3)Nb_(2/3))_(0.25)(Ti_(0.53)Zr_(0.47))_(0.75)O_3 ceramics sintered with Ag electrodes at 900℃ for multilayer piezoelectric actuator

CuO added Pb0.92Sr0.06Ba0.02（Mg1/3Nb2/3）0.25（Ti0.53Zr0.47）0.75O3 ceramics were studied to prepare high-quality multilayer piezoelectric actuators with pure Ag electrodes at 900 ℃. CuO addition not only reduced the sintering temperature significantly from 1260 ℃ to 900 ℃ but also improved the ceramic density to 7.742 g/cm3. The 0.7 wt.% CuO added ceramic sintered at 900 ℃ shows the remnant polarization （Pr） of 40 μC/cm2, 0.28% strain at 40 kV/cm, and the piezoelectric coefficient （d33） of 630 pC/N. This ceramic shows a strong relaxor characteristic with a Curie temperature of 200 ℃. Furthermore, the 0.7 wt.% CuO added ceramic and pure Ag electrodes were co-fired at 900 ℃ to prepare a high-quality multilayer piezoelectric actuator with a d33 of over 450 pC/N per ceramic layer.

Preparation and Structure of Rainbow Piezoelectric Ceramics

Rainbow piezoelectric ceramics are a new type of stress-biased,oxide-reduced composite ferroelectric ceramics,which have a special dome structure.The have shown excellent properties such as ultra-high displacement under an applied electric field and enhanced load-bearing capability.In this article,their manufacture,structures and properties were discussed in detail by combining experiments and theory analysis.The resuts show that the optimal conditions for producing Rainbow samples from PLZT ceramics were determined to be 900℃ for 1 to 1.5 hours.A number of different phases have been found in the reduced layer of Rainbow ceramics by XRD analyses.The phases found include metallic lead and other oxide phases,such as PbO,ZrO 2 and TiO 2.The original PLZT phase was not observed.The reduced layer was transgranularly fractured while the unreduced ceramic was intergranularly fractured.Two kinds of fracture types can be seen at the interface,which denotes the different degrees of reduction.It is shown that the Pb grains (about 0.2μm) constitute a continuous phase in the reduced layer,which accounts for the good electrical conductivity.

Achieving remarkable piezoelectric activity in Sb-Mn co-modified CaBi_(4)Ti_(4)O_(15) piezoelectric ceramics

CaBi_(4)Ti_(4)O_(15)(CBT)-based Aurivillius high-temperature piezoceramics with different Sb-Mn co-doping amounts were synthesized via the conventional sintering technique.The influences of doping amount on the product were studied via their crystal structure,microstructure,and piezoelectric performance.It is found that an appropriate Sb-Mn co-doping amount can effectively optimize the crystal structure and decrease the oxygen vacancy concentration in CBT ceramics,leading to enhanced electrical properties.Optimized electrical performance with a high Curie temperature(TC)of 792℃and a remarkable piezoelectric coefficient(d33)of 25 p C/N were achieved at a doping amount(x)of 0.05.Furthermore,this ceramic is found to exhibit an excellent thermal stability,with d33 retaining 88%of its original value after annealing at 600℃for 2 h.Moreover,this ceramic shows a high electrical resistivity(ρ)of 1.35×10^(8)Ω·cm with a small dielectric loss(tanδ)of 1.7%at 400℃.Because of such outstanding piezoelectric performance,it is believed that these Sb-Mn co-doped CBT ceramics could be potential candidates for high-temperature piezoelectric applications.