Anisotropy in domain engineered 0.92Pb(Zn1/3 Nb2/3)O3-0.08PbTiO3 single crystal and analysis of its property fluctuations

The orientation dependence of slowness and electromechanical coupling coefficients of 0.92Pb(Zn/sub 1/3/Nb/sub 2/3/)O/sub 3/-0.08PbTiO/sub 3/ (PZN-8%PT) domain engineered single crystal was analyzed based on the measured complete set of elastic, piezoelectric, and dielectric constants. There exist one quasi-longitudinal, one quasi-shear, and one pure shear wave in each of the [100]-[010], [010]-[001], and [001]-[110] planes. The slowness of the quasi-shear wave exhibits strong anisotropy in all three planes, and the coupling coefficient k/sub 33/ and k/sub 31/ reach their maximum in [001] and [110] directions of cubic axis, respectively. Because the composition of the PMN-8%PT system is very close to the morphotropic phase boundary, the extraordinary large piezoelectric coefficients d/sub 31/ and d/sub 33/, and high coupling coefficient k/sub 33/ are very sensitive to compositional variation. We have performed error analysis and proposed an improved characterization scheme to derive a complete data set with best consistency.     

Full tensorial elastic, piezoelectric, and dielectric properties characterization of [011]-poled PZN-9%PT single crystal

Transverse piezoelectric property of 0.91Pb(Zn(1/3)Nb(2/3))O(3)-0.09PbTiO(3) (PZN-9%PT) single crystal poled along [011] direction under different fields have been investigated, the poling field giving the best property was between 350 and 650 V/mm at room temperature. Full tensorial elastic, dielectric, and piezoelectric properties of PZN-9%PT single crystal poled along the [011] direction under 500 V/mm have been determined by resonance and ultrasonic methods. It was found that the electromechanical coupling coefficients k(32) and k(33) can reach 0.90 and 0.89 and the piezoelectric coefficients d(32) and d(15) are -1705 and 2012 pC/N, respectively. This complete set of physical properties can provide convenience for piezoelectric device fabrication and domain engineering studies.     

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).     

Linear electro-optic properties of orthorhombic PZN-8%PT single crystal

The optical transmittance spectra of relaxor ferroelectric 0.92Pb(Zn(1/3)Nb(2/3))O(3)-0.08PbTiO(3) (PZN-8%PT) single crystals poled along different directions have been systematically studied at room temperature. After being poled along the [011] direction, the transmittance of induced orthorhombic PZN-8%PT single crystal is more than 50% from 0.5 to 5.7 μm, which is much higher than that poled along the [001] and [111] directions. The refractive indices and linear electro-optic properties of the orthorhombic PZN-8%PT single crystal were characterized at a wavelength of 632.8 nm. Large electro-optic responses were observed, (γ33) = 220 pm/V, (γ13) = 62 pm/V, and (γ23) = 23 pm/V. Thus, orthorhombic PZN-8%PT single crystal is a promising material for high-performance electro-optic devices.     

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.     

Single crystal PZN/PT-polymer composites for ultrasound transducer applications

Single crystal relaxor ferroelectrics of PZN-8%PT were investigated for potential application in ultrasound transducers. The full set of electromechanical properties was determined using combined resonance and laser interferometry techniques. Ultra-high length extensional coupling (k(33)) of 0.94 was observed, a 25% increase over Navy Type VI PZT ceramics. The thickness extensional coupling (k(t)) of 0.48 was comparable to PZT compositions, and the compliance S(33)(E) was a factor of six greater. To maximize height extensional coupling (k'(33)), while minimizing length extensional coupling k(31) in array elements, it was necessary to align the elements along the 100 crystallographic direction in the x-y plane. Mode coupling plots and test samples for array elements determined that width-to-height ratios of less than 0.5 were desired, similar to the requirement for polycrystalline PZT ceramics. Modeling of 1-3 composites and experimental results demonstrated that thickness coupling greater than 0.80 could be achieved with a 40% to 70% volume fraction of PZN-PT. Although this is a substantial increase over PZT 1-3 composites, with a thickness coupling coefficient of 0.66, it represents a smaller fraction of the length extensional coupling k(33). This reduction may be a consequence of the increased compliance of PZN-PT, which results in significant clamping by the polymer matrix. Ultrasonic transducers fabricated using PZN-8%PT 1-3 composites achieved experimental bandwidths as high as 141%. The pulse-echo responses displayed good agreement with modeled results using the Redwood equivalent circuit.     

Complete set of material properties of [011](c) poled 0.24Pb(In(1/2)Nb(1/2))O(3)-0.46Pb(Mg(1/3)Nb(2/3))O(3)-0.30PbTiO(3) single crystal

A complete set of elastic, piezoelectric, and dielectric constants of [011](c) poled multidomain 0.24Pb(In(1/2)Nb(1/2))O(3)-0.46Pb(Mg(1/3)Nb(2/3))O(3)-0.30PbTiO(3) ternary single crystal has been determined using resonance and ultrasonic methods and the temperature dependence of the dielectric permittivity has been measured at 3 different frequencies. The experimental results revealed that this [011](c) poled ternary single crystal has very large transverse piezoelectric coefficient d(32) = -1693 pC/N, transverse dielectric constant ε(11)/ε(0) ~ 7400 and a high electromechanical coupling factor k(32) ~ 90%. In addition, its coercive field is 2 times of that of the corresponding binary 0.7Pb(Mg(1/3)Nb(2/3))O(3)-0.30PbTiO(3) single system with much better temperature stability. Therefore, the crystal is an excellent candidate for transverse mode electromechanical devices.     

A 3.7 MHz phased array probe using 0.91Pb(Zn(1/3)Nb(2/3))O(3)-0.09PbTiO(3 )

A novel 128-channel phased array probe for echocardiography with a center frequency of 3.7 MHz using 0.91Pb(Zn(1/3)Nb(2/3))O(3)-0.09PbTiO(3 ) (PZN-9%PT) single crystal has been fabricated to realize greater sensitivity and broader bandwidth properties. The echo amplitude of the PZN-9%PT single-crystal probe is about 5 dB higher than that of the conventional lead airconate titanate (PZT) ceramic probe, and the fractional bandwidth is about 25 percentage points broader. The quality of B mode images obtained by the PZN-9%PT probe satisfies the performance of the two types of conventional PZT ceramic probes that have center frequencies of 2.5 and 3.75 MHz. At the reference frequency of 3 MHz, the Doppler sensitivity of the PZN-9%PT probe is about 5 dB higher than that of the 3.75 MHz PZT probe; the blood flow of a pulmonary vein in a hard-to-image patient is much more clearly imaged than in the case of using the PZT probe. These superior images are attributable to the use of sufficiently large PZN-9%PT single crystals obtained by the self-flux method.     

Nondestructive evaluation of large-area PZN-8%PT single crystal wafers for medical ultrasound imaging probe applications

A nondestructive quality evaluation and control procedure for large-area, (001)-cut PZN-8%PT wafers is described. The crystals were grown by the flux technique engineered to promote (001) layer growth of the crystals. The wafers were sliced parallel to the (001) layer growth plane. Curie temperature (Tc) variations, measured with matching arrays of dot electrodes (of 5.0 mm in center-to-center spacing), were found to be better than +/- 4.0 degrees C both within wafers and from wafer to wafer. After selective dicing to give final wafers of narrower Tc distributions (e.g., +/- 3.0 degrees C or better), the wafers were coated with complete electrodes and poled at room temperature at 0.7-0.9 kV/mm. Typical overall properties of the poled wafers were: K3T = 5,200 (+/- 10% from wafer to wafer), tan delta < 0.01 (all wafers), and kt = 0.55 (+/- 5%) (all percentage variations are in relative percentages). Then, the distributions of K3S, tan delta, and kt were measured by the array dot electrode technique. The variations in K3S (hence K3T) and kt within individual wafers were found to be within +/- 10% and +/- 5%, respectively. The dielectric loss values, measured at 1 kHz, were consistently low, being < 0.01 throughout the wafers. The kt values determined by the dot electrodes were found to be about 5% smaller than those obtained with the complete electrodes, which can be attributed to an increase in capacitance ratio due to the partial electroding. The k33 values, deduced using the relation K3S approximately (1 - k33(2))K3T, from the mean K3S and overall K3T values, average 0.94 (+/- 2%). The present work shows that the distribution of Tc within wafers can be used as a convenient check for the uniformity in composition and electromechanical properties of PZN-8%PT single crystal wafers. Our results show that, to control deltaK3T and deltakt within individual wafer to < or = 10% and 5%, respectively, the variation in Tc within the wafer should be kept within +/- 3.0 degrees C or better.     

Pure low-frequency flexural mode of [011](c) poled relaxor-PbTiO(3) single crystals excited by k(32) mode

Rhombohedral phase relaxor-PbTiO(3) solid solution single crystals poled along [011](c) exhibits superior lateral extensional piezoelectric response, which enables the excitation of a pure low frequency flexural mode with a bridge-type electrode configuration. For the ternary 0.24Pb(In(1/2)Nb(1/2)) O(3)-0.46Pb(Mg(1/3)Nb(2/3))O(3)-0.30PbTiO(3) single crystal poled along [011](c), the electromechanical coupling factor of the flexural mode reached as high as 0.66, and the resonance frequency of this mode can be easily made in kHz range, making it possible to fabricate very small size low frequency sensors and actuators. We have delineated theoretically the coupling between flexural mode and other modes and realized a strong pure flexure mode.     

Electromechanical coupling properties of [001], [011] and [111] poled Pb(Mg1/3Nb2/3)O3-0.32PbTiO3 single crystals

The electric field induced “butterfly” curves and polarization loops, and the stress induced strain and polarization responses of [001], [011] and [111] oriented Pb(Mg_1/3Nb_2/3)O₃-0.32PbTiO₃ (PMN-0.32 PT) relaxor ferroelectric single crystals have been systematically investigated by experiment study. The focus is on the effect of constant compressive bias stress on the electromechanical coupling behavior along three crystallographic directions of PMN-0.32 PT single crystals. Dependence of the coercive field, remnant polarization, dielectric constant, and piezoelectric coefficient on the bias stress has been quantified for PMN-0.32 PT single crystals oriented in three different directions. Obtained results show that the large piezoelectric responses under zero compressive stress in [001] and [011] orientation are dominated by intrinsic crystal lattice while the engineered domain structure has a relatively minor effect. It is found that observed responses under stress cycle for [001] oriented crystals are due to polarization rotation and phase transformations. However, those for [011] and [111] oriented crystals are due to domain switching. The “butterfly” curves and polarization loops driven by electric field under different bias compression are described by two non-180° domain switching.     

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.     

High-frequency ultrasonic transducer fabricated with lead-free piezoelectric single crystal

High-frequency (25 MHz) ultrasonic transducers with Na(0.5)Bi(0.5)TiO(3)-BaTiO(3) (NBT-BT) lead-free piezoelectric single crystal as the active elements are fabricated and characterized. The impedance measurement reveals that the poled [001]-oriented NBT-BT single crystal exhibits a high thickness electromechanical coefficient k(t) of 0.52 and a low clamped dielectric constant of 80. The -6-dB bandwidth of the transducer is 46.16% and the insertion loss at the center frequency is -31.89 dB. The good performance of the transducer indicates that the NBT-BT single crystal would be a promising lead-free material for ultrasonic transducer applications.     

分凝对Pb(Mg1/3Nb2/3)O3-38%PbTiO3单晶的成分及介电、压电性能的影响

研究了用改进的Bridgman法生长的PMNT62/38单晶在其生长过程中的分凝现象,研究了分凝导致的成分不均匀及其对介电和压电性能的影响.XRFA分析表明,PMNT62/38单晶底部的PbTiO3(PT)含量为x=35.2mol％,而顶部的PT含量为43mol％.底部晶体(001),(110)和(111)三种切型的晶片加电场极化后,其介电和压电性能出现了异常的现象.(110)切型的压电模量最大,为1200pC/N;(111)次之,为789pC/N;(001)最低,为371pC/N.极化后的(110)和(111)晶片在室温、1kHz频率下的相对介电常数(两种切型的εr都在10000左右),约为(001)晶片(ε_r-5000)的1倍,并且介电常数在低温端有上升的趋势.     

Orientation dependence of electromechanical properties of relaxor based ferroelectric single crystals

The orientation dependence of electromechanical properties of relaxor based ferroelectric single crystals Pb(Zn_1/3Nb_2/3)O₃–(6–7)%PbTiO₃ and Pb(Mg_1/3Nb_2/3)O₃–33%PbTiO₃ has been calculated by coordinate transformation. Different from previous studies, the optimum cutting orientations have been predicted in terms of their piezoelectric responses in the corresponding crystal planes. The calculation results indicated that the anisotropic piezoelectric effects of [001] _c and [011] _c poled multi-domain crystals mainly come from the intrinsic contribution. However, the strong dielectric anisotropy of [001] _c poled multi-domain crystals mainly comes from extrinsic domain and domain wall contributions. For [011] _c poled multi-domain crystals, the intrinsic orientation effect enhances the dielectric anisotropy.     

Measurements along the growth direction of PMN-PT crystals: dielectric, piezoelectric, and elastic properties

Property measurements are reported for Pb(Mg1/3Nb2/3)03-PbTiO3 (PMN-PT) single crystals grown along (001) by a seeded-melt method. Chemical segregation occurs during crystal growth, leading to property changes along the growth direction. Variations in dielectric, piezoelectric, and elastic properties were evaluated for specimens selected from the crystals. Room-temperature data are correlated with Tc and composition that ranged from 27 to 32% PT, i.e., in the vicinity of the morphotropic phase boundary (MPB). While there was little change in the high electromechanical coupling factor k33 (0.87-0.92), both the piezoelectric charge coefficient d33 (1100-1800 pC/N) and the free dielectric constant K3 (4400-7000) were found to vary significantly with position. Increases in d33 and KT33 were relatively offsetting in that the ratio yielded a relatively stable piezoelectric voltage coefficient g33 (27-31 x 10(-3) Vm/N). Values are also reported for the elastic compliance (3.3-6.3 x 10(-11) m2/N) determined from resonance measurements. Enhancements in d33 and K(T)33 were associated with lattice softening (increasing sE33) as the composition approached the MPB. Details are reported for the piezoelectric, dielectric, and elastic properties as a function of growth direction, Tc, and composition. The results are useful for an understanding of properties in PMN-PT crystals and for the design of piezoelectric devices.     

分凝对Pb(Mg1/3Nb2/3)O3-38%PbTiO3单晶的成分及介电、压电性能的影响

研究了用改进的Bridgman法生长的PMNT62／38单晶在其生长过程中的分凝现象，研究了分凝导致的成分不均匀及其对介电和压电性能的影响。XRFA分析表明，PMNT62／38单晶底部的PbTiO3(PT)含量为x=35.2mol%，而顶部的PT含量为43mol%。底部晶体（001），（110）和（111）三种切型的晶片加电场极化后，其介电和压电性能出现了异常的现象。（110）切型的压电模量最大，为1200pC/N；（111）次之，为789pC/N；（001）最低，为371pC/N。极化后的（110）和（111）晶片在室温、1kHz频率下的相对介电常数（两种切型的εr都在10000左右），约为（001）晶片（εr-5000)的1倍，并且介电常数在低温端有上升的趋势。     

Influence of spinel substrate and over-layer for enhanced SAW and AO properties with KNbO3 thin film

Surface acoustic wave (SAW) propagation characteristics have been studied using modeling calculations for a potassium niobate (KNbO/sub 3/) thin film-layered structure with [001] and [110] orientation on a single crystal spinel (MgAl/sub 2/O/sub 4/) substrate, and a spinel buffer layer on silicon. Variation in the electromechanical coupling and acoustic attenuation has been compared. A significantly high value of coupling factor (k/sub max//sup 2/=23%) is obtained for the [001]KNbO/sub 3//spinel structure by introducing an optimum thickness of spinel over-layer for potential wide bandwidth SAW device applications. The dispersion characteristics with the [110] KNbO/sub 3/ orientation indicate an initial peak in the coupling coefficient value (k/sub max//sup 2/=8.8%) at a relatively low KNbO/sub 3/ film thickness that appears attractive for fabricating devices with thinner films. The KNbO/sub 3/ film with [001] orientation is found attractive for efficient acousto-optic (AO) device application with the formation of a symmetric waveguide structure (spinel(0.5 /spl mu/m)/KNbO/sub 3/(1.0 /spl mu/m)/spinel). A high value of k/sup 2/=23.5% with 50% diffraction efficiency has been obtained for the spinel(0.5 /spl mu/m)/KNbO/sub 3/(1.0 /spl mu/m)/spinel structure at 1 GHz SAW frequency and 633 nm optical wavelength at a very low input drive power of 15.4 mW.     

Phase-transition temperatures and piezoelectric properties of (Bi1/2Na1/2)TiO3-(Bi1/2Li1/2)TiO3-(Bi1/2K1/2)TiO3 lead-free ferroelectric ceramics.

The phase-transition temperatures and piezoelectric properties of x(Bi(1/2)Na(1/2))TiO3-y(Bi(1/2)Li(1/2))TiO3-z(Bi(1/2)K(1/2))TiO3 [x + y + z = 1] (abbreviated as BNLKT100(y)-100(z)) ceramics were investigated. These ceramics were prepared using a conventional ceramic fabrication process. The phase-transition temperatures such as depolarization temperatures T(d), rhombohedraltetragonal phase transition temperature T(R-T), and dielectric-maximum temperature T(m) were determined using electrical measurements such as dielectric and piezoelectric properties. The X-ray powder diffraction patterns of BNLKT100(y)-100(z)) show the morphotropic phase boundary (MPB) between rhombohedral and tetragonal at approximately z = 0.20, and the piezoelectric properties show the maximum at the MPB. The electromechanical coupling factor k(33), piezoelectric constant d(33) and T(d) of BNLKT4-20 and BNLKT8-20 were 0.603, 176 pC/N, and 171 degrees C, and 0.590, 190 pC/N, and 115 degrees C, respectively. In addition, the relationship between d33 and Td of tetragonal side and rhombohedral side for BNLKT4-100z and BNLKT8-100z were presented. Considering both high Td and high d(33), the tetragonal side of BNLKT4-100z is thought to be the superior composition. The d(33) and T(d) of BNLKT4-28 were 135 pC/N and 218 degrees C, respectively. Moreover, this study revealed that the variation of T(d) is related to the variation of lattice distortion such as rhombohedrality 90-alpha and tetragonality c/a.     

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℃.