A double-mode piezoelectric single-crystal ultrasonic micro-actuator

Ternary Pb(In(1/2)Nb(1/2))O(3)-Pb(Mg(1/3)Nb(2/3))O(3)-PbTiO(3) (PIN-PMN-PT) single crystals with higher coercive field (E(C) ~9 kV/cm) and higher ferroelectric-transition temperature (T(R-T) = 108°C) were grown, and correspondingly, a double-mode piezoelectric ultrasonic micro-actuator made of PIN-PMN-PT crystal brick (5 x 1.5 x 1.32 mm) and operated in the first longitudinal and the second bending modes was developed. The ferroelectric, dielectric, electromechanical, and resonance displacement properties of the micro-actuator were characterized for miniature linear piezo-motor applications. The longitudinal displacement of the actuator is ~0.11 μm (with an applied voltage of 5 V), which is comparable to that of a multilayer piezoelectric-ceramic actuator of the same size. This crystal micro-actuator was successfully used to drive a slider moving linearly.     

Electromechanical properties of Pb(In(1∕2)Nb(1∕2))O(3)-Pb(Mg(1∕3)Nb(2∕3))O(3)-PbTiO(3) single crystals

The Pb(In(1∕2)Nb(1∕2))O(3)-Pb(Mg(1∕3)Nb(2∕3))O(3)-PbTiO(3) (PIN-PMN-PT) crystals were studied as function of phase and orientation. The properties, including the Curie temperature T(C), ferroelectric-ferroelectric phase transition temperature T(R∕O-T), coercive field, and piezoelectric∕dielectric responses, were systematically investigated with respect to the composition of PIN-PMN-PT crystals. The Curie temperature T(C) was found to increase from 160 to 220 °C with ferroelectric-ferroelectric phase transition temperature T(R-T) and T(O-T) being in the range of 120-105 °C and105-50 °C, respectively. The piezoelectric activity of PIN-PMN-PT crystals was analyzed by Rayleigh approach. The ultrahigh piezoelectric response for domain engineered [001] (1600-2200 pC∕N) and [011] (830-1550 pC∕N) crystals was believed to be mainly from the intrinsic contribution, whereas the enhanced level of piezoelectric and dielectric losses at the compositions around morphotropic phase boundaries (MPBs) was attributed to the phase boundaries motion.     

Relaxor-PT single crystals: observations and developments

Relaxor-PT based ferroelectric single crystals Pb(Zn?/?)Nb(?/?)O?-PbTiO? (PZNT) and Pb(Mg?/?)Nb(?/?)O?-PbTiO? (PMNT) offer high performance with ultra-high electromechanical coupling factors k?? > 0.9 and piezoelectric coefficients d??s > 1500 pC/N. However, the usage temperature range of these perovskite single crystals is limited by T(RT)-the rhombohedral to tetragonal phase transition temperature, which occurs at significantly lower temperatures than the Curie temperature T(C), a consequence of curved morphotropic phase boundaries (MPBs). Furthermore, these <001>-oriented crystals exhibit low mechanical quality Q and coercive fields, restricting their usage in high-power applications. In this survey, recent developments on binary and ternary perovskite relaxor-PT crystal systems are reviewed with respect to their temperature usage range. General trends of dielectric and piezoelectric properties of relaxor-PT crystal systems are discussed in relation to their respective T(C)/T(RT). In addition, two approaches have been implemented to improve mechanical Q, including acceptor dopants, analogous to hard polycrystalline ceramics, and anisotropic domain engineering, enabling low-loss crystals with high coupling for high-power applications.     

Electric-field and stress effects on depoling and overpoling phenomena in [001]-poled transverse mode Pb(Zn1/3Nb2/3)O3-(6-7)%PbTiO3 single crystal of [110] length cut

Solid-solution Pb(Zn(1/3)Nb(2/3))O(3)-PbTiO(3) (PZN-PT) single crystals, touted as next-generation piezoelectric materials, have been studied extensively in the past decade. This work addresses the advantages and limitations of transducers made of transverse mode PZN-(6-7)%PT single crystals of [110](L) X [001](T)(P) cut. This cut exhibits superior electromechanical properties, with k(31) ≈ 0.85 and d(31) ≈-1450 pC/N, and an extremely high d(31)/S(E)(11) value of >35 C/m(2). It also has relatively high overpoling, i.e., rhombohedralto- tetragonal phase transformation, field of ≈2 kV/mm. This overpoling field further decreases with increase in axial compressive stress. Despite these good attributes, this crystal cut has a low depoling field of ≤ 0.3 kV/mm, a result of low coercive fields of [001]-poled relaxor-based single crystals, which decreases further with increasing axial compressive stress, limiting its bipolar drive capability. The axial compressive stress required to cause overpoling via rhombohedral-to-tetragonal phase transformation of relevant domain variants in the crystal is found to be >90 MPa. In contrast, this crystal cut depolarizes at comparatively low axial tensile stress of ≈15 MPa, the magnitude of which is not significantly affected by the moderate forward field applied.     

Face shear piezoelectric properties of relaxor-PbTiO(3) single crystals

Poling relaxor-PbTiO(3) single crystals along pseudocubic [011] results in a macroscopic symmetry of mm2, enabling a large face shear d(36) in Zt±45° cut crystals. In order to allow the determination of electrical properties by the resonance method, square samples are required. Using Pb(In(0.5)Nb(0.5))O(3)-Pb(Mg(1∕3)Nb(2∕3))O(3)-PbTiO(3) crystals, piezoelectric d(36) coefficients were determined to be in the range of 2000-2500 pC∕N, with electromechanical coupling factor k(36)～0.80-0.83. Mechanical quality factor Q～180 and ultralow frequency constant of ～500 Hz m were obtained. Together with the wide temperature usage range (up to ～110 °C) and high ac driving field stability (～5 kV∕cm), such face shear crystals have a promising potential for ultralow-frequency-transducer applications.     

Domain size engineering in tetragonal Pb(In(1∕2)Nb(1∕2))O(3)-Pb(Mg(1∕3)Nb(2∕3))O(3)-PbTiO(3) crystals

The effect of domain size on the dielectric and piezoelectric properties of [111]-oriented tetragonal Pb(In(1∕2)Nb(1∕2))O(3)-Pb(Mg(1∕3)Nb(2∕3))O(3)-PbTiO(3) crystals was investigated. The dielectric permittivity (?(33?) (T)∕?(0)) and piezoelectric coefficient (d(33)) were found to be on the order of 13 800 and 1630 pC∕N, respectively, for samples with domain size of ～500?nm, a 3-fold increase to crystals with domain size of ～50?μm. Rayleigh analysis revealed that the extrinsic contribution to the piezoelectric response increased from ～8% to 30% with decreasing domain size, due to the increased domain wall density and associated irreversible domain wall motion. The enhanced properties were thought to relate to the fine domain structures, however, showing a poor electric field and temperature stabilities with domain size of 500?nm. Of particular significance is that samples with domain size being on the order of 5?μm exhibit field and temperature stabilities, with yet high piezoelectric properties, make it potential for transducer applications.     

Recent developments in high curie temperature perovskite single crystals

The temperature behavior of various relaxor-PT piezoelectric single crystals was investigated. Owing to a strongly-curved morphotropic phase boundary, the usage temperature of these perovskite single crystals is limited by T/sub R-T/- the rhombohedral to tetragonal phase transformation temperature - which occurs at the significantly lower temperatures than the Curie temperature T/sub c/. Attempts to modify the temperature usage range of Pb(Zn/sub 1/3/Nb/sub 2/3/)O/sub 3/-PbTiO/sub 3/ (PZNT) and Pb(Mg/sub 1/3/Nb/sub 2/3/)O/sub 3/-PbTiO/sub 3/ (PMNT) rhombohedral crystals (T/sub c/ /spl sim/ 150-170/spl deg/C, T/sub R-T/ /spl sim/ 60-120/spl deg/C) using minor dopant modifications were limited, with little success. Of significant potential are crystals near the morphotropic phase boundary in the Pb(Yb/sub 1/2/Nb/sub 1/2/)O/sub 3/-PbTiO/sub 3/ (PYNT) system, with a T/sub c/ > 330/spl deg/C, even though T/sub R-T/ was found to be only half the value at /spl sim/160/spl deg/C. Single crystals in the novel BiScO/sub 3/-PbTiO/sub 3/ system offer significantly higher T/sub c/s > 400/spl deg/C, while exhibiting electromechanical coupling coefficients k/sub 33/ > 90% being nearly constant till the T/sub R-T/ temperature around 350/spl deg/C, which greatly increases the temperature range for transducer applications.     

Dielectric and piezoelectric properties of perovskite materials at cryogenic temperatures

Dielectric and piezoelectric properties of perovskite materials including La modified Pb(Zr, Ti)O3 (PZT's), (Ba, Sr)TiO3 (BST) polycrystalline ceramics and Pb(Zn1/3 Nb2/3)O3-PbTiO3 (PZN-PT) single crystals were investigated for capacitor and actuator applications at cryogenic temperatures. PZTs were compositionally engineered to have decreased Curie temperatures (Tc) by La and Sn doping in order to compensate for the loss of extrinsic contributions to piezoelectricity at cryogenic temperatures. Enhanced extrinsic contributions resulted in piezoelectric coefficients (d33) as high as 250 pC/N at 30 K, superior to that of conventional DOD Type PZT's (d33~100 pC/N). This property enhancement was associated with retuning to the MPB at cryogenic temperatures. 5/95 BST with a dielectric maximum at 57 K was investigated to obtain high electrostrictive properties or E-field induced piezoelectricity. Coupling coefficients (k31) 25% comparable to those of the cryogenic PLZT piezoelectrics were observed at d.c. bias of 1.5 kV/cm and 50 K. Though significantly lower than the room temperature values, PZN-PT rhombohedral single crystals exhibited d33> 500 pC/N at 30 K.     

Highly polarized single-c-domain single-crystal Pb(Mn,Nb)O(3)-PZT thin films

In-plane unstrained single-c-domain/single-crystal thin films of PZT-based ternary ferroelectric perovskite, ξPb(Mn,Nb)O3-(1 - ξ)PZT, were grown on SrRuO(3)/Pt/MgO substrates using magnetron sputtering followed by quenching. The sputtered unstrained thin films exhibit unique ferroelectric properties: high coercive field, Ec > 180 kV/cm, large remanent polarization, P(r) = 100 μC/cm(2), small relative dielectric constants, ε* = 100 to 150, high Curie temperature, Tc = ~600 °C, and bulk-like large transverse piezoelectric constants, e31,f = -12.0 C/m(2) for PZT(48/52) at ξ = 0.06. The unstrained thin films are an ideal structure to extract the bulk ferroelectric properties. Their micro-structures and ferroelectric properties are discussed in relation to the potential applications for piezoelectric MEMS.     

Investigation of single and multidomain Pb(In(0.5)Nb(0.5))O(3)-Pb(Mg(1∕3)Nb(2∕3))O(3)-PbTiO(3) crystals with mm2 symmetry

The piezoelectric properties of Pb(In(0.5)Nb(0.5))O(3)-Pb(Mg(1∕3)Nb(2∕3))O(3)-PbTiO(3) crystals with various engineered domain configurations were investigated. Rhombohedral and monoclinic∕orthorhombic crystals poled along their crystallographic [011] directions were found to possess macroscopic mm2 symmetry, with "2R" and "1O" domain, respectively. Crystals with the "2R" domain configuration were found to exhibit high extensional piezoelectric coefficients d(33) (～1300 pC∕N) and d(32) (～-1680 pC∕N), while crystals with the "1O" configuration possessed high shear coefficients d(15) (～3500 pC∕N) and d(24) (～2070 pC∕N), with relatively low extensional piezoelectric coefficients d(33) (～340 pC∕N) and d(32) (～-260 pC∕N). The observed results were explained by "polarization rotation" model, as related to their respective domain configurations.     

Characterization of flux-grown PZN-PT single crystals for high-performance piezo devices

Relaxor ferroelectric Pb(Zn(1/3)Nb(2/3))O(3-x)PbTiO(3) (PZN-PT) and Pb(Mg(1/3)Nb(2/3))O(3)-PbTiO(3)(PMN-PT) single crystals are the potential candidates for future high-performance piezoelectric devices due to their exceptionally high dielectric and piezoelectric properties. Characterization on flux-grown PZN-PT single crystals of different orientations revealed that PZN-(6-7)%PT single crystals show good homogeneity in dielectric and electromechanical properties and composition. When poled in [001] direction, these crystals exhibit high longitudinal-mode properties with dielectric constant (K(T)) approximately equal to 7000, piezoelectric coefficients (d(33)) approximately equal to 2800 pC/N, and electromechanical coupling factors (k(33)) > or = 0.92. For [011]-cut crystals, optimally poled PZN-7%PT single crystal exhibits very high transverse-mode dielectric and piezoelectric properties with K(T) > or = 5000, d(32) approximately equal to -3800 pC/N and k(32) > or = 0.90. [011]- poled PZN 6%PT has d(32) approximately equal to -3000 pC/N and comparable k(32) and K(T) values. In comparison with melt-grown PMNPT single crystals, flux-grown PZN-PT single crystals show good compositional homogeneity, superior and consistent dielectric and electromechanical properties, and higher depolarization temperatures (TDP).     

SrCO3掺杂对PMN-PMnN-PZT-Ce压电陶瓷储能及介电弛豫性能的影响

通过铌铁矿先驱法制备了Pb(Mg_(1/3)Nb_(2/3))O_3-Pb(Mn_(1/3)Nb_(2/3))O_3-PbZrO_3-PbTiO_3+0.3%CeO_2(质量分数)+xSrCO_3(PMN-PMnN-PZT-Ce-xSr,x=0.00,0.03,0.05,0.07)四元系压电陶瓷,研究了SrCO_3含量的变化对Pb(Mg_(1/3)Nb_(2/3))O_3-Pb(Mn_(1/3)-Nb_(2/3))O_3-PbZrO_3-PbTiO_3+0.3%CeO_2(质量分数)(PMN-PMnN-PZT-Ce)压电陶瓷相结构、储能密度以及弛豫行为的影响。通过XRD表明,样品为单一稳定的钙钛矿结构,并且存在准同晶界(MPB);当x=0.07时,在外加电场60kV/cm下取得较好的储能性能:储能密度W1=0.31J/cm~3,储能效率η=0.47;通过修正Curie-Weise定律,较好地描述了陶瓷弥散相变的特征,弥散相变系数γ随着Sr~(2+)掺杂量的增加而增加。当x=0.07时,γ取得最大值1.972 8,此时弛豫现象最明显。     

铌镁酸铋-钛酸铅压电陶瓷准同型相界附近的性能和相变温度研究

利用传统固相烧结法制备了Bi(Mg_2/3Nb_1/3)O₃-PbTiO₃(BMN-PT)压电陶瓷, 分析了不同PbTiO₃含量对BMN-PT压电陶瓷的晶体结构、介电、压电及铁电性能的影响. XRD结果表明: 合成的BMN-PT陶瓷具有纯钙钛矿结构, 并且在PbTiO₃含量为x=0.60时, 其组分的XRD图谱在衍射角2θ=45°出现明显的分峰, 说明该组分相结构中存在三方和四方相的共存. 压电铁电性能显示, BMN-0.60PT有最大的压电常数d₃₃(~170pC/N)和平面机电耦合系数k_p(0.35), 最小的矫顽场E_c(29.4 kV/cm)及最大的剩余极化P_r(31.4 μC/cm²). 确定了BMN-PT压电陶瓷的准同型相界(MPB)为PbTiO₃含量x=0.60的组分. 介电系数温谱表明介电系数峰值温度(Tm)随着PbTiO₃含量的增大而升高, MPB组分的Tm约为276℃.     

Quadratic electro-optic properties of Pb(Mg1/3Nb2/3)O3-PbTiO3 transparent ceramics under both DC and AC bias

The basic quadratic electro-optic properties of Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) transparent ceramics have been studied under both DC and AC electric field bias. The contribution of piezoelectric resonance to electro-optic effect for this quadratic electro-optic ceramics material has been experimentally demonstrated and theoretically analyzed. It is found that, at the piezoelectric resonance frequencies, the piezoelectric induced electro-optic effect dominates and leads to a dramatically high sensitivity for weak electric signal detection. About 20 dB signal-to-noise ratio is attained when detecting AC electric field strength of 1 V/m with optimized DC bias. Besides, the effects of AC frequency and amplitude on halfwave voltage V(π) of PMN-PT are investigated.     

弛豫铁电单晶及织构陶瓷的研究进展

综述了近年来弛豫铁电单晶和织构陶瓷的制备及其介电、压电性能的研究进展。弛豫铁电单晶的制备方法主要有高温溶液法、布里奇曼法和固态再结晶法，尺寸可达40mm以上，(001)切片压电常数d33最大可达3000pC／N，k3达到0.93，但是成分不均匀仍是影响晶体压电性能的一个主要因素。织构陶瓷的制备方法主要为固态再结晶法(TGG法和RTGG法)，其耗时短、成本低，压电性能可达到单晶的60％～80％，介电常数甚至可以超过部分单晶，是一个新的发展方向。     

铌酸钠钾基压电陶瓷的结构与性能研究

采用传统的固相反应合成法制备了结构较为致密的0.9(K0.5Na0.5)NbO3-0.1LiSbO3(KNN-LS)无铅压电陶瓷,研究了其相结构、压电、介电、损耗以及铁电性质.常温下的压电陶瓷具备四方钙钛矿结构,具有较高的压电系数d33=131pC/N和低的介电损耗tanδ=0.09(10kHz)等优点.另外,常温下的KNN-LS陶瓷存在着较为饱满的电滞回线,其剩余极化率Pr为16.1μC/cm2,矫顽场为EC=14.8kV/cm.性能较KNN压电陶瓷有了较大的提高.     

Large electric-field-induced strain in ferroelectric crystals by point-defect-mediated reversible domain switching

Ferroelectric crystals are characterized by their asymmetric or polar structures. In an electric field, ions undergo asymmetric displacement and result in a small change in crystal dimension, which is proportional to the applied field. Such electric-field-induced strain (or piezoelectricity) has found extensive applications in actuators and sensors. However, the effect is generally very small and thus limits its usefulness. Here I show that with a different mechanism, an aged BaTiO(3) single crystal can generate a large recoverable nonlinear strain of 0.75% at a low field of 200 V mm(-1). At the same field this value is about 40 times higher than piezoelectric Pb(Zr, Ti)O(3) (PZT) ceramics and more than 10 times higher than the high-strain Pb(Zn(1/3)Nb(2/3))O(3)-PbTiO(3) (PZN-PT) single crystals. This large electro-strain stems from an unusual reversible domain switching (most importantly the switching of non-180 degrees domains) in which the restoring force is provided by a general symmetry-conforming property of point defects. This mechanism provides a general method to achieve large electro-strain effect in a wide range of ferroelectric systems and the effect may lead to novel applications in ultra-large stroke and nonlinear actuators.     

Defect control for polarization switching in BiFeO₃ single crystals

BiFeO? (BFO) single crystals were grown and the effects of Zn and Mn co-doping on the polarization and leakage current properties were investigated at 25 °C for establishing materials design based on defect chemistry. Although Zn doping or Mn doping led to a deterioration in the properties, Zn-Mn co-doping led to a large remanent polarization (36 μC/ cm2), a low coercive field (19 kV/cm), and a relatively low leakage current density (~10?? A/cm2). It is proposed that defect dipoles composed of Zn2+ and Mn?+ act as effective nucleation sites for ferroelectric domains during polarization switching in BFO crystals.     

80-MHz intravascular ultrasound transducer using PMN-PT free-standing film

[Pb(Mg(1/3)Nb(2/3))O(3)](0.63)[PbTiO(3)](0.37) (PMN-PT) free-standing film of comparable piezoelectric properties to bulk material with thickness of 30 μm has been fabricated using a modified precursor coating approach. At 1 kHz, the dielectric permittivity and loss were 4364 and 0.033, respectively. The remnant polarization and coercive field were 28 μC/cm(2) and 18.43 kV/cm. The electromechanical coupling coefficient k(t) was measured to be 0.55, which was close to that of bulk PMN-PT single-crystal material. Based on this film, high-frequency (82 MHz) miniature ultrasonic transducers were fabricated with 65% bandwidth and 23 dB insertion loss. Axial and lateral resolutions were determined to be as high as 35 and 176 μm. In vitro intravascular imaging on healthy rabbit aorta was performed using the thin film transducers. In comparison with a 35-MHz IVUS transducer, the 80-MHz transducer showed superior resolution and contrast with satisfactory penetration depth. The imaging results suggest that PMN-PT free-standing thin film technology is a feasible and efficient way to fabricate very-high-frequency ultrasonic transducers.     

Piezoelectric, dielectric, optical and electrical characterization of solution grown flower-like ZnO nanocrystal

Flower-like ZnO nanocrystals were grown by low temperature solution technique after controlling Zn²⁺/OH⁻ ratio. The morphology and structural studies confirmed the formation of nano structure, revealing the [0001] oriented growth of the ZnO nanorods. The variation of dielectric constant, loss, ac conductivity and activation energy as a function of frequency was studied. In UV-Vis absorption spectra, a sharp absorption band-edge at 355 nm is observed from which direct optical band gap 3.40 eV was calculated. In P-E hysteresis piezoelectric characterization for unpoled ZnO, the value of remnant polarization and coercive field was found to be 16.31 µC/cm² and 6.11 kV/cm respectively which increased to 25.65 µC/cm² and 8.35 kV/cm, respectively after poling at 1 kV/cm. The piezoelectric charge coefficient (d₃₃) was found to be 1.7 pC/N.