Unconventional piezoelectric coefficients in perovskite piezoelectric ceramics

Piezoelectric ceramics exhibit three conventional piezoelectric coefficients,i.e.,d33,d31,d15,due to their∞mm crystal symmetry.Unconventional piezoelectric coefficients,such as d11,d12,d13,d14,d16,etc.,can only be extracted from piezoelectric single crystals of special symmetry with specific cut direction.Here we demonstrate a rotated poling method to realize unconventional piezoelectric coefficients in perovskite piezoelectric ceramics.This method is elaborated in theory and experimentally proven to be effective.Full nonzero piezoelectric coefficients in the 36 piezoelectric coefficients matrix can be obtained by combining these“quasi(effective)piezoelectric coefficients”with the conventional piezoelectric coefficients,which would expand applications in a wide variety of piezoelectric devices.

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.

Thermal and piezoelectric properties of Bi_(3.15)Nd_(0.85)Ti_3O_(12) thin film prepared by metal organic decomposition

Bi3.15Nd0.85Ti3O12 （BNT） powder and thin film were prepared by metal organic decomposition （MOD） method. The heat flow curve of BNT powder was measured with a modulated temperature differential scanning calorimeter, and thermal physical parameters such as thermal conductivity coefficient and thermal diffusion coefficient were obtained from the heat flow curve. The phase identification, ferroelectric, and piezoelectric properties of BNT thin film annealed at 700℃ were investigated with X-ray diffractometer, ferroelectric analyzer, and scanning probe microscope. The results show that the thin films consisting of a single phase of bismuth-layered perovskite are polycrystalline, without a preferred orientation. Remnant polarization 2Pr is 63.2 μC/cm2 under 530 kV/cm applied field, and the effective piezoelectric coefficient d33 is 30 pm/V.

Preparation and characterization of Sr0.5Ba0.5Nb2O6 glass-ceramic on piezoelectric properties

We studied the influence of heat treatment time on the optical, thermal, electrical, and mechanical properties of stron- tium barium niobate （Srl-xBaxNb206; hereafter SBN） piezoelectric glass-ceramics with tungsten bronze-type structure, which have good piezoelectric properties and are important lead-free piezoelectric materials. We found that the best heat treatment time is 4 h. The properties of the prepared materials are better than that of SBN ceramics and the glass-ceramic growth is faster than the SBN crystal when the heat treatment time of the SBN piezoelectric glass-ceramic is controlled, reducing the preparation costs greatly.

Evaluations of dielectric property and drug release profile of 5-FU patches based on plasma charged electrets

In the present study,the electret 5-fluorouracil patch was developed,the effective surface potential,piezoelectric coefficient d33,open-circuit thermally stimulated discharge（TSD） current spectra and shear adhesion of the patch were measured.The drug release profile of the patch was determined by using high performance liquid chromatography method.A stable potential difference which was positively dependent on the surface potential of the electret was generated on two sides of the patch.The measurements of d33 coefficient,TSD current spectra and adhesion performance showed that the electrostatic field of the electret could cause polarization and cohesive strength decreasing of the matrix molecules,change the distribution and interaction of the drug molecules in patch,therefore to increase the release of drug from the transdermal patch.

Ca^2+ doping effects in(K,Na,Li)(Nb0.8Ta0.2)O3 lead-free piezoelectric ceramics

Lead-free(K0.5-x/2Na0.5-x/2Lix)(Nb0.8Ta0.2)O3(KNLNT)and(K0.49-x/2Na0.49-x/2-LixCa0.01)(Nb0.8Ta0.2)O3(KNLNT-Ca)ceramics were prepared by a conventional ceramic processing.Structural analysis shows that the Ca^2+ doping takes the A site of ABO3 perovskite and decreases the phase transition temperature.Property measurements reveal that as a donor dopant,the Ca^2+ doping results in higher room-temperature dielectric constant,lower dielectric loss,and lower mechanical quality factor.In addition,the Ca^2+ doping does not change the positive piezoelectric coefficient d33,but increases the converse piezoelectric coefficient d 33*significantly.This is likely due to the increase in the relaxation,as well as the appearance of(CaNa/K·-VNa/K’)defect dipoles.

Outstanding electromechanical performance in piezoelectric ceramics via synergistic effects of defect engineering and domain miniaturization

Piezoelectric ceramics with high mechanical quality factor Q_(m) and large piezoelectric coefficient d_(33) are urgently required for advanced piezoelectric applications.However,obtaining both of these prop-erties simultaneously remains a difficult challenge due to their mutually restrictive relationship.Here 0.5Pb(Ni_(1/3)Nb_(2/3))O_(3)-0.5Pb(Zr_(0.3)Ti_(0.7))O_(3) piezoceramic with tetragonal(T)-rich MPB is designed as a matrix to construct the defect engineering by doping low-valent Mn ions.The strong coupling of defect dipole and T-rich phase can effectively hinder the rotation of P_(s),restrict domain wall motion and improve Q_(m).At the same time,the substituted Mn ions will introduce local random field,destroying the long-range or-dering of ferroelectric domain and reducing domain size.The miniaturized domain structure can increase poling efficiency and inhibit the reduction of d_(33).Guided by this strategy,Q_(m) has increased by more than 10 times and d_(33) has only decreased by about 25%.The optimized electromechanical performance with Q_(m)=822,d_(33)=502 pC/N,k_(p)=0.55 and tanδ=0.0069 can be obtained in the present study.

Dielectric and piezoelectric perfomance of lead-free ceramics of boron sodium gadolinate niobate at morphotropic phase boundary

New lead-free piezoceramic nanocomposites of Boron Sodium Gadolinium Niobate(BNGN),with general formula(1-x)B_(0.5)Na_(0.5)GdO3xB_(0.5)Na_(0.5)NbO_(3),exhibiting a Morphotropic Phase Boundary(MPB),have been synthesized following hydrothermal method followed by solid state sintering.The occurrence of MPB at the composition with x=0.55,at which rhombohedral and monoclinic phases are found to coexist,has been confirmed using powder XRD.This accounts for the occurrence of large remnant polarization when the sintered ceramic pellets are subjected to electric poling at 2KV/mm.Uniform microstructure of various compositions is confirmed by SEM imaging.Dielectric and piezoelectric properties of the samples are found to be comparable to those of commercial grade PZT.At the MPB,the d_(33)coefficient is found to be 556 pC/N,which is close to that of commercial grade PZT,which makes BNGN a promising material to substitute lead containing PZT in the near future.

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.

Temperature dependence of the mechanical and electrical properties of soft-doped lead zirconate titanate under compression and impact

Compared to a quasistatic environment,the electromechanical response of piezoelectric ceramics exhibits a considerably nonlinear behavior when subjected to impact.If the effect of ambient temperature is further considered,then the situation becomes more unpredictable.The thermal,mechanical,and electrical properties of soft-doped piezoelectric ceramics(PZT-5H)under compression and impact conditions were analyzed in the temperature range of-60℃to 200℃(below Curie temperature).The experimental results indicate that the fracture strength of PZT-5H has an extreme value near room temperature.The dynamic piezoelectric coefficient is strongly temperature dependent and has a maximum value near 100℃because of the“electric devil's staircase effect”between polarization and domain switching threshold.These temperature-dependent data will enable the accurate prediction of the dynamic performance of devices by computer simulation.

Mechanical properties of Ni_(0.83)Co_(0.15)Cu_(0.02)Fe_(1.9)O_(4-δ)+PbZr_(0.52)Ti_(0.48)O_(3)particulate composites by composite oscillator technique and the correlation with the results of magnetoelectric properties

The xNi_(0.83)Co_(0.15)Cu_(0.02)Fe_(1.9)O_(4-δ)+PbZr_(0.52)Ti_(0.48)O_(3)(PZT)particulate magneto ferroelectric composites with x=0,0.1,0.2,0.3,0.4,0.5 and 0.6 mole fraction were prepared by conventional ceramic double sintering method.The presence of two phases(perovskite structure of ferroelectric phase and spinal structure of ferromagnetic phase)was confirmed by X-ray diffraction.The magnetoelectric(ME)property of the particulate composites was determined at room temperature as a function of intensity of magnetic field.The temperature variation of the longitudinal modulus(L)and the internal friction(Q−1)of these particulate composites at 104.3 kHz was studied in the wide temperature range 30-420℃.The temperature variation of the longitudinal modulus in each composition of these particulate composites showed two abrupt minima.One minimum coincided with the ferroelectric-paraelectric Curie transition temperature(θE)and the other with the ferromagnetic-paramagnetic Curie transition temperature(θM).The internal friction measurement also showed two sharp peaks in each composition corresponding to those temperatures where the minima were noticed in the temperature variation of the longitudinal modulus behaviour.

Study on properties of tantalum-doped La_(2)Ti_(2)O_(7) ferroelectric ceramics

A series of ceramics with a general formula,La_(2)Ti_(2-x)Ta_(x)O_(7),in which x=0.05;0.1;0.2;and 0.3,were prepared by Spark Plasma Sintering(SPS).Effects of tantalum substitution for titanium on the structure,dielectric,and piezoelectric properties were studied.Results revealed that the structure changed gradually from 4-layer to 3-layer due to the higher valence of Ta.The solid solution limit of tantalum in La_(2)Ti_(2)O_(7)lattice was in the proximity of x=0.2.The ferroelectric Curie temperature(Tc)decreased with increasing tantalum doping content.dc resistivity reached a maximum value at x=0.2 with a value of~1.0×10^(8)Ωcm at 600℃.The influence of texture on the piezoelectric properties of La_(2)Ti_(2-x)Ta_(x)O_(7)ceramics was also investigated.A maximum d_(33)value~2:1 pC/N was obtained at x=0.2.