New Sm-PMN-PT Ceramic-Based 2-D Array for Low-Intensity Ultrasound Therapy Application.

A two-dimensional (2-D) array with a small pitch (approximately 0.5λ in medium) can achieve complete 3-D control of ultrasound beams without grating lobes and enable the generation of multiple focal spots simultaneously, which is a desired tool for noninvasive therapy. However, the large electrical impedance of 2-D array elements owing to their small size results in a low energy transfer efficiency between a 2-D array and an electrical system, thereby limiting their practical applications.

Transparent ferroelectric crystals with ultrahigh piezoelectricity.

Transparent piezoelectrics are highly desirable for numerous hybrid ultrasound-optical devices ranging from photoacoustic imaging transducers to transparent actuators for haptic applications. However, it is challenging to achieve high piezoelectricity and perfect transparency simultaneously because most high-performance piezoelectrics are ferroelectrics that contain high-density light-scattering domain walls. Here, through a combination of phase-field simulations and experiments, we demonstrate a relatively simple method of using an alternating-current electric field to engineer the domain structures of originally opaque rhombohedral Pb(MgNb)O-PbTiO (PMN-PT) crystals to simultaneously generate near-perfect transparency, an ultrahigh piezoelectric coefficient d (greater than 2,100 picocoulombs per newton), an excellent electromechanical coupling factor k (about 94 per cent) and a large electro-optical coefficient γ (approximately 220 picometres per volt), which is far beyond the performance of the commonly used transparent ferroelectric crystal LiNbO.

Giant piezoelectricity of Sm-doped Pb(MgNb)O-PbTiO single crystals.

High-performance piezoelectrics benefit transducers and sensors in a variety of electromechanical applications. The materials with the highest piezoelectric charge coefficients ( ) are relaxor-PbTiO crystals, which were discovered two decades ago. We successfully grew Sm-doped Pb(MgNb)O-PbTiO (Sm-PMN-PT) single crystals with even higher values ranging from 3400 to 4100 picocoulombs per newton, with variation below 20% over the as-grown crystal boule, exhibiting good property uniformity.

Ultrahigh piezoelectricity in ferroelectric ceramics by design.

Piezoelectric materials, which respond mechanically to applied electric field and vice versa, are essential for electromechanical transducers. Previous theoretical analyses have shown that high piezoelectricity in perovskite oxides is associated with a flat thermodynamic energy landscape connecting two or more ferroelectric phases. Here, guided by phenomenological theories and phase-field simulations, we propose an alternative design strategy to commonly used morphotropic phase boundaries to further flatten the energy landscape, by judiciously introducing local structural heterogeneity to manipulate interfacial energies (that is, extra interaction energies, such as electrostatic and elastic energies associated with the interfaces).

High-Performance Ultrasound Needle Transducer Based on Modified PMN-PT Ceramic With Ultrahigh Clamped Dielectric Permittivity.

A modified Pb(MgNb)O-PbTiO (PMN-PT) polycrystalline ceramic with ultrahigh relative clamped dielectric permittivity ( ) and high piezoelectric properties ( pC/N, ) was used to fabricate high-frequency miniature ultrasound transducers. A 39-MHz high-frequency ultrasound needle transducer with a miniature aperture of 0.4 mm mm was designed and successfully characterized.

The origin of ultrahigh piezoelectricity in relaxor-ferroelectric solid solution crystals.

The discovery of ultrahigh piezoelectricity in relaxor-ferroelectric solid solution single crystals is a breakthrough in ferroelectric materials. A key signature of relaxor-ferroelectric solid solutions is the existence of polar nanoregions, a nanoscale inhomogeneity, that coexist with normal ferroelectric domains. Despite two decades of extensive studies, the contribution of polar nanoregions to the underlying piezoelectric properties of relaxor ferroelectrics has yet to be established.

New Pb(Mg1/3Nb2/3)O3-Pb(In1/2Nb1/2)O3-PbZrO3-PbTiO3 Quaternary Ceramics: Morphotropic Phase Boundary Design and Electrical Properties.

Four series of Pb(Mg1/3Nb2/3)O3-Pb(In1/2Nb1/2)O3-PbZrO3-PbTiO3 (PMN-PIN-PZ-PT) quaternary ceramics with compositions located at the morphotropic phase boundary (MPB) regions were prepared. The MPBs of the multicomponent system were predicted using a linear combination rule and experimentally confirmed by X-ray powder diffraction and electrical measurement. The positions of MPBs in multicomponent systems were found in linear correlation with the tolerance factor and ionic radii of non-PT end-members.

Variation of Piezoelectric properties and mechanisms across the relaxor-like/Ferroelectric continuum in BiFeO3- (K0.5Bi0.5)TiO3-PbTiO3 ceramics.

1- x - y)BiFeO3-x(K0.5Bi0.5)TiO3-yPbTiO3 (BFKBT- PT) piezoelectric ceramics were investigated across the compositional space and contrasted against the xBiFeO3- (1-x)(K0.

Growth and properties of Li, Ta modified (K,Na)NbO lead-free piezoelectric single crystals.

Li, Ta modified (K,Na)NbO single crystals with the size of 18 mm × 18 mm × 10 mm were successfully grown by top-seeded solution growth method, with orthorhombic-tetragonal phase transition temperature ~79 °C and Curie temperature ~276 °C. The electromechanical coupling factors and were found to be ~88% and ~65%, respectively. The piezoelectric coefficient for the [001] poled crystals reached 255 pC/N.

Relaxor-PbTiO3 single crystals for various applications.

Piezoelectric materials lie at the heart of electromechanical devices. Applications include actuators, ultrasonic imaging, high intensity focused ultrasound, underwater ultrasound, nondestructive evaluation transducer, pressure sensors, and accelerometers, to name a few. In this work, the advantages and disadvantages of relaxor-PbTiO(3)-based single crystals are discussed, based on the requirements (figure of merit) of various applications, with emphasis on recent developments of the shear properties of single crystals as a function of temperature and applied fields.

Hydrostatic piezoelectric properties of [011] poled Pb(MgNb)O-PbTiO single crystals and 2-2 lamellar composites.

The hydrostatic piezoelectric properties of [011] poled Pb(MgNb)O-PbTiO (PMN-PT) crystals and corresponding 2-2 crystal/epoxy composites were investigated. The crystal volume ratio and compositional dependencies of the hydrostatic charge and voltage coefficients ( and ) and hydrostatic figure of merit (FOM)    were determined, where large FOM value of 3.2 pm/N with high stability as a function of hydrostatic pressure was achieved for rhombohedral crystal composites.

1-3 piezoelectric composites for high temperature transducer applications.

High temperature Pb(Zr,Ti)O /epoxy 1-3 composites were fabricated using the dice and fill method. The epoxy filler was modified with glass spheres in order to improve the thermal reliability of the composites at elevated temperatures. Temperature dependent dielectric and electromechanical properties of the composites were measured after aging at 250°C with different dwelling times.

Complete set of elastic, dielectric, and piezoelectric constants of [011] poled rhombohedral Pb(InNb)O-Pb(MgNb)O-PbTiO:Mn single crystals.

Mn modified rhombohedral Pb(InNb)O-Pb(MgNb)O-PbTiO (PIN-PMN-PT:Mn) single crystals poled along [011] crystallographic direction exhibit a "2R" engineered domain configuration, with macroscopic symmetry. The complete sets of material constants were determined using combined resonance and ultrasonic methods, and compared to [001] poled PIN-PMN-PT:Mn crystals. The thickness shear piezoelectric coefficient and electromechanical coupling factor were found to be on the order of ∼3000 pC/N and 0.

Elastic, dielectric and piezoelectric characterization of single domain PIN-PMN-PT: Mn crystals.

Mn modified 0.26Pb(In(1/2)Nb(1/2))O(3)-0.42Pb(Mg(1/3)Nb(2/3))O(3)-0.

Electroacoustic response of 1-3 piezocomposite transducers for high power applications.

The electroacoustic performance of 1-3 piezoelectric composite transducers with low loss polymer filler was studied and compared to monolithic Pb(Zr,Ti)O(3) (PZT) piezoelectric transducers. The 1-3 composite transducers exhibited significantly high electromechanical coupling factor (k(t) ∼ 0.64) when compared to monolithic counterparts (k(t) ∼ 0.

Characterization of piezoelectric ceramics and 1-3 composites for high power transducers.

The high power characteristics of various piezoelectric ceramics and 1-3 composites were investigated. In contrast to "hard" Pb(Zr,Ti)O(3), modified (Bi(0.5)Na(0.

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 (ɛ(33 ) (T)∕ɛ(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.

Critical Property in Relaxor-PbTiO(3) Single Crystals --- Shear Piezoelectric Response.

The shear piezoelectric behavior in relaxor-PbTiO(3) (PT) single crystals is investigated in regard to crystal phase. High levels of shear piezoelectric activity, d(15) or d(24) >2000 pC N(-1), has been observed for single domain rhombohedral (R), orthorhombic (O) and tetragonal (T) relaxor-PT crystals. The high piezoelectric response is attributed to a flattening of the Gibbs free energy at compositions proximate to the morphotropic phase boundaries, where the polarization rotation is easy with applying perpendicular electric field.

Thickness Dependent Properties of Relaxor-PbTiO(3) Ferroelectrics for Ultrasonic Transducers.

The electrical properties of Pb(Mg(1/3)Nb(2/3))O(3)-PbTiO(3) (PMN-PT) based polycrystalline ceramics and single crystals were investigated as a function of scale ranging from 500 microns to 30 microns. Fine-grained PMN-PT ceramics exhibited comparable dielectric and piezoelectric properties to their coarse-grained counterpart in the low frequency range (<10 MHz), but offered greater mechanical strength and improved property stability with decreasing thickness, corresponding to higher operating frequencies (>40 MHz). For PMN-PT single crystals, however, the dielectric and electromechanical properties degraded with decreasing thickness, while ternary Pb(In(1/2)Nb(1/2))O(3)-Pb(Mg(1/3)Nb(2/3))O(3)-PbTiO(3) (PIN-PMN-PT) exhibited minimal size dependent behavior.

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.

Influence of Domain Size on the Scaling Effects in Pb(Mg1/3Nb2/3)O3-PbTiO3 Ferroelectric Crystals.

The property degradation observed in thin Pb(Mg(1/3)Nb(2/3))O(3)-PbTiO(3) (PMN-PT) crystals is believed to relate to large domains and subsequent clamping induced by surface-boundary. In this work, the properties were investigated as function of domain size, using controlled poling. The degraded piezoelectric and dielectric properties of thin PMN-PT were found to increase significantly, by decreasing domain size.

Recent Developments on High Curie Temperature PIN-PMN-PT Ferroelectric Crystals.

Pb(In(0.5)Nb(0.5))O(3)-Pb(Mg(1/3)Nb(2/3))O(3)-PbTiO(3) (PIN-PMN-PT) ferroelectric crystals attracted extensive attentions in last couple years, due to their higher usage temperatures range (> 30°C) and coercive fields (~5kV/cm), meanwhile maintaining similar electromechanical couplings (k(33)> 90%) and piezoelectric coefficients (d(33)~1500pC/N), when compared to their binary counterpart Pb(Mg(1/3)Nb(2/3))O(3)-PbTiO(3).

Dielectric and electromechanical properties of rare earth calcium oxyborate piezoelectric crystals at high temperatures.

The electrical resistivity, dielectric, and electromechanical properties of ReCa(4)O(BO(3))(3) (ReCOB; Re = Er, Y, Gd, Sm, Nd, Pr, and La) piezoelectric crystals were investigated as a function of temperature up to 1000 °C. Of the studied crystals, ErCOB and YCOB were found to possess extremely high resistivity (p): p > 3 × 10(7) ω.cm at 1000 °C.

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.

Temperature independent shear piezoelectric response in relaxor-PbTiO(3) based crystals.

The temperature dependence of the shear piezoelectric responses in relaxor-PbTiO(3) based perovskite crystals with rhombohedral, orthorhombic, and tetragonal phases were investigated. Based on thermodynamic analysis, high shear piezoelectric coefficients (d(24)) and good thermal stability were predicted in orthorhombic crystals, owing to the "vertical" orthorhombic-rhombohedral phase boundary. By resonance measurements, shear piezoelectric coefficient d(24) was found to be on the order of ∼2100 pC∕N at room temperature, maintaining same value over the temperature range of -50-100 °C.