Lead Zinc Niobate-lead Titanate Research Articles

PZN-PT single crystal based high-frequency intravascular ultrasound transducers

Cardiovascular disease (CVD) is a kind of high life-threatening illness for humans. Intravascular ultrasound (IVUS) technology could highly help the physicians to know the condition of human's vessel wall. In this work, the novel lead zinc niobate-lead titanate (PZN-PT) single crystals-based IVUS transducers were prepared. The electrical properties of PZN-PT single crystals were investigated with high d33 of 2531 pC/N and dielectric constant. The high piezoelectric response could improve the transmission and receive properties of IVUS transducers. Moreover, the high dielectric constant (8050) could highly help the miniaturization of IVUS transducer. The IVUS transducers have a center frequency at 43.5 MHz and a -6dB bandwidth of 62.3%. It promising the PZN-PT based IVUS transducers are suitable for the clinical diagnosis field for CVD.

Development of Cardiac Phased Array With Large-Size PZN-5.5 %PT Single Crystals.

In recent years, the manufacturing process of lead zinc niobate-lead titanate [Pb(Zn1/3Nb2/3)O3-PbTiO3, also called PZN-PT], has been enhanced with improvements in size, consistency, and a suitable compromise between piezoelectric properties and phase transition temperature, which means that it is possible to obtain PZN-PT single crystals in sufficient size for performance characterization studies and batch manufacturing to produce high-performance medical ultrasonic transducers. This article mainly focuses on the development of the 64-element phased array ultrasonic transducer based on novel large-size PZN-PT piezoelectric single crystals. The composition of the single crystal was chosen as PZN-5.5 %PT. The designed center frequency of the phased array is 3.0 MHz, which is suitable for cardiac ultrasound imaging. The array elements were spaced at a 0.254-mm pitch, and interconnected through a custom-designed flexible circuit. Double matching layers with a light backing structure were applied in the transducer fabrication process to improve the performance of the array. The test results of the developed phased array showed a center frequency of 3.0 MHz, and an average -6 dB fractional bandwidth of 72%. In the vicinity of the center frequency, the two-way insertion loss (IL) was about -46 dB, while a crosstalk between the adjacent elements was less than -31 dB. The wire phantom can be distinctly imaged with the phased array, and the axial and lateral resolutions were measured to be 660 and [Formula: see text], respectively. The image of a standard phantom was acquired to present the imaging performance of the transducer. The final results indicate that the transducer arrays based on novel large-size PZN-PT single crystals are quite promising for use in medical ultrasound imaging applications.

Electric Field Tuning of Magnetism in Fe3O4/Pt/PZN-PT Heterostructures Prepared by Atomic Layer Deposition

Tuning of magnetic properties by electric field (E-field) has received extensive attentions because it is compact, fast, and energy efficient. Here, multiferroic heterostructures of Fe3O4/Pt/PZN-PT (011) (lead zinc niobate-lead titanate single piezoelectric substrate) were in situ fabricated by atomic layer deposition (ALD) using C10H10Fe and O2 as precursors at a low temperature (400 °C) without a subsequent annealing process in H2 atmosphere, which is beneficial in combining with traditional silicon-based semiconductor technology. The E-field dependence of the magnetic anisotropy was studied systematically by ferromagnetic resonance spectroscopy with the larger tunable in-plane magnetic anisotropy of 152 Oe and 318 Oe obtained along the [100] and [0–11] axes, corresponding to the largest magnetoelectric coupling coefficient of 31.8 Oe.cm/kV. Also, the tunable out-of-plane magnetic anisotropy of 35 Oe was obtained along the [011] axis. The outstanding E-field tuning magnetism in the Fe3O4/Pt/PZN-PT heterostructures offers significant possibilities for novel multiferroic devices.

Effect of donor dopants on the properties of flux grown PZN-PT single crystals

Rare-earth Nd-doped lead zinc niobate-lead titanate (Nd:PZN-PT) and W-doped lead zinc niobate-lead titanate (W:PZN-PT) single crystals have been grown by self-flux technique and their dielectric, ferroelectric and piezoelectric properties have been investigated. Pure perovskite phases were observed, and lattice parameters were obtained by Rietveld refinement. Diffuse phase transition and frequency dispersive phenomena was observed in the dielectric peaks confirming the enhancement of relaxor behaviour for doped crystals. Variation of dielectric constant (e), AC conductivity and piezoelectric charge coefficient (d33) as a result of doping is investigated in detail. From the hysteresis behaviour, it was evident that a simple domain switching mechanism was observed for doped crystals.

Revisiting the structural stability and electromechanical properties in lead zinc niobate-lead titanate-barium titanate (PZN-PT-BT) ternary system

Lead zinc niobate-lead titanate (PZN-PT) system is of particular interest for scientific researches and commercial applications due to the unique relaxation feature and superior electromechanical responses. However, it is difficult to prepare polycrystalline ceramics near the morphotropic phase boundary due to the stability of a competing lead niobate pyrochlore phase. BaTiO3 (BT) was reported to be an effective perovskite phase stabilizer at a cost of reduction in Curie temperature and piezoelectric properties. Herein, the amount of BT in PZN-PT-BT system and the sintering conditions were optimized to simultaneously stabilize the perovskite phase and maintain high dielectric and piezoelectric response. An optimum piezoelectric coefficient d33 ∼ 870 pC/N along with a Tm ∼ 133 °C and an electromechanical coupling coefficient k33 ∼ 0.61 was obtained in the PZN-8PT-6BT ceramics sintered at 1100 °C. The low sintering temperature, wide processing window, and improved dielectric and piezoelectric properties make PZN-PT-BT ceramics potential candidates for piezoelectric devices.

Electric field tunable high-frequency performance in high-resistivity Fe0.5Co0.5-MgO/lead zinc niobate-lead titanate nanogranular film multiferroic heterostructures

Fe0.5Co0.5-MgO films with composition gradient were fabricated by sputter deposition onto (011) lead zinc niobate-lead titanate substrates. The addition of MgO in excess of its solubility in the FeCo alloy results in the formation of amorphous grain boundaries, leading to a dramatic increase of the resistivity with values over 20 times that of pure FeCo films. As a result, a large self-bias ferromagnetic resonance frequency fFMR of up to 9.87 GHz is obtained in the absence of an external magnetic field (H = 0 A/m) and an electric field tuning frequency range of 4.55 GHz was achieved in the as-deposited films at an electric field of 7 kV/cm. The high resistivity and high fFMR in these heterostructures provide great opportunities for application in self-bias tunable monolithic microwave integrated circuit devices.

Electric field control of the exchange spring effect in perpendicularly magnetized FePt/NiFe bilayers

The electric field control of the exchange spring (ES) effect in perpendicularly magnetized bilayers is studied using micromagnetic simulation. The ES bilayer with a total thickness of 20 nm is composed of a FePt layer with perpendicular magnetic anisotropy (PMA) and a NiFe layer with in-plane anisotropy. The thickness ratio between the FePt and NiFe layers (TRFN) is varied. Single-crystal lead zinc niobate-lead titanate (PZN-PT) forms the piezoelectric substrate, and electric fields are applied across the thickness of the substrate to induce in-plane stress. The results reveal that application of a negative electric field E reduces the switching field (HS) and squareness ratio (MR/MS) but enhances the nucleation field (HN), while applying a positive E has a negligible effect on these parameters. When the TRFN is 18:2, an electric field of −2 MV/m reduces HS by 5.5% while MR/MS is maintained at 1. This indicates that when the FePt content is sufficiently large, applying a strong negative E can reduce HS without changing MR/MS. Based on the simulation results, we propose a model for electrically assisted magnetic memory.

Electric field tunability of microwave soft magnetic properties of Co2FeAl Heusler alloy film

Co2FeAl Heusler alloy film with 100 nm in thickness was sputtered on (011)-cut lead zinc niobate-lead titanate (PZN-PT) single crystal slabs. It was revealed that this multiferroic laminate shows very large electric field (E-field) tunability of microwave soft magnetic properties. With the increase of electric field from 0 to 8 kV/cm on PZN-PT, the anisotropy field, HK, of the Co2FeAl film along [100] direction of PZN-PT is dramatically enhanced from 65 to 570 Oe due to the strong magnetoelectric (ME) coupling between ferromagnetic Co2FeAl film and ferroelectric substrate. At the same time, the damping constant α of Co2FeAl film dramatically decreases from 0.20 to 0.029. As a result, a significantly shift of self-biased ferromagnetic resonance frequency, fFMR, from 1.86 to 6.68 GHz with increment of 3.6 times was obtained. These features demonstrate that Co2FeAl/PZN-PT multiferroic laminate is promising in fabrication of E-field tunable microwave components.

Large E-field tunability of magnetic anisotropy and ferromagnetic resonance frequency of co-sputtered Fe50Co50-B film

Fe27.45Co30.19B42.36 (referred to as FeCoB) films with 100 nm in thickness were co-sputtered on (011)-cut lead zinc niobate-lead titanate (PZN-PT) single crystal substrate under RF powers of 80 W for Fe50Co50 target and 120 W for B target, respectively. The anisotropy field HK of the FeCoB/PZN-PT multiferroic composite is increased by more than 10 times, from 56 to 663 Oe under the E-field from 0 to 7 kV/cm due to the strong magnetoelectric coupling, corresponding to a large tunability of HK of 86.7 Oe cm/kV. At the same time, the self-bias ferromagnetic resonance frequency fFMR is dramatically shifted upwards by an electric field from 2.57 to 9.02 GHz with an increment of 6.45 GHz, corresponding to E-field tunablity of fFMR 921.4 MHz.cm/kV. These features demonstrate that FeCoB/PZN-PT multiferroic laminates prepared under an integrated circuits process are promising in fabrication of E-field tunable monolithic microwave integrated circuits (MMIC) devices and their components.

Large E-field tunability of microwave ferromagnetic properties in Fe59.3Co28.0Hf12.7/PZN-PT multiferroic composites

Strong converse magnetoelectric coupling was observed in a multiferroic heterostructure of Fe59.3Co28.0Hf12.7 film on (011) cut lead zinc niobate-lead titanate (PZN-PT) slab, which exhibited a large electric field (E-field) tunability of microwave magnetic properties. With the increase of E-field from 0 to 6 kV/cm on PZN-PT, the ferromagnetic resonance (FMR) field Hr shifts downwards by 430.7 Oe along [011¯] direction and upwards by 492.9 Oe along [100] direction of the PZN-PT. Accordingly, the strong magnetoelectric coupling led to a significantly enhanced self-biased FMR frequency from 4.2 to 7.9 GHz under zero bias magnetic field, and the magnetic damping constant α was decreased from 0.0260 to 0.0185 at the same time. These features demonstrate that this multiferroic laminate is promising in fabrication of E-field tunable microwave components.

Crossings of Lamb modes in lead zinc niobate-lead titanate crystal plates

Frequency dispersions of Lamb waves in [001]c and [011]c polarized lead zinc niobate-lead titanate crystal free infinite plates are studied based on the partial wave theory. Multiple crossings between symmetric and antisymmetric Lamb modes are found only in [001]c polarized crystals, and most of the dispersion relations would exhibit the same rule as that in lead magnesium niobate-lead titanate crystals. It is found that multiple crossings between A0 and S0 modes are directly related to the multivalued quasishear vertical slowness curves. A pair of complex conjugate roots of the wave number in the x3 direction is found in a certain area. Equation of elastic constants is obtained when A0 and S0 modes cross under this condition, which can be conveniently used to judge whether A0 and S0 modes cross for crystals with orthogonal and tetragonal symmetries.

Electrostatic tuning of ferromagnetic resonance and magnetoelectric interactions in ferrite-piezoelectric heterostructures grown by chemical vapor deposition

Magnetoelectric interactions as a function of applied electric field have been studied in ferrite-ferroelectric heterostructures at microwave frequencies. The measurements are performed on 1.5–2.0 μm thick nickel ferrite (NiFe2O4) films grown heteroepitaxially on lead zinc niobate-lead titanate and lead magnesium niobate-lead titanate substrates using direct liquid injection chemical vapor deposition. Large shifts in the ferromagnetic resonance profile are observed in these heterostructures due to strong magnetoelectric coupling resulting from electrostatic field induced changes in the magnetic anisotropy field. Theoretical estimates of field shifts are in good agreement with the experimental data.

Electric field modulation of surface anisotropy and magneto-dynamics in multiferroic heterostructures

The effects of an electric field on the magneto-dynamics of a FeGaB/PZN-PT (lead zinc niobate-lead titanate) multiferroic heterostructure were investigated. It was found that with the increase of electric field applied on the PZN-PT layer, the magnetoelectric coupling is increased, and the magnetization of the FeGaB film changes gradually from an unpinned to a pinned boundary condition at the FeGaB/PZN-PT interface. This change leads to the observation of the first-order standing spin wave mode and the varied resonance intensity ratio between the standing mode and the uniform mode from 1 to 5% in the FMR spectra. The E-field induced surface anisotropy change confirms the strain mediated magnetoelectric mechanism through the interface between multiferroic heterostructures.

Tunable magnetoresistance devices based on multiferroic heterostructures

Surface-effect induced strong magnetoelectric (ME) coupling was investigated in ultrathin Ni80Fe20/PZN-PT (lead zinc niobate-lead titanate) multiferroic heterostructures. Giant electric field (E-field) tuning of the magnetic anisotropy, ferromagnetic resonance field, coercive field and anisotropic magnetoresistance were demonstrated through strain mediated ME coupling in 10 nm thick Ni80Fe20/PZN-PT multiferroic heterostructures. E-field dynamic modulation of magnetoresistance was also displayed. These provide great opportunities for electrostatic tunable MR devices.

Microwave magnetoelectric effects in bilayers of piezoelectrics and ferrites with cubic magnetocrystalline anisotropy

The strain mediated microwave magnetoelectric coupling is studied in bilayers of ferrites with cubic anisotropy and piezoelectrics. The strength of magnetoelectric coupling is determined from data on ferromagnetic resonance frequency shift Δf versus applied electric field E. Studies at 6–10 GHz on samples of nickel zinc ferrite and polycrystalline lead zirconium titanate, lead magnesium niobate–lead titanate or lead zinc niobate-lead titanate (PZN–PT) show shifts Δf on the order of 30–150 MHz for E=10 kV/cm. Bilayers of nickel zinc ferrite and PZN-PT demonstrated the highest magnetoelectric coefficient of 5.3 Oe cm/kV. Theoretical estimates of the frequency shifts are in very good agreement with the data.

Ferroelectric properties of ruthenium-doped lead zinc niobate-lead titanate single crystal

Using atomic force microscopy and piezoresponse force microscopy (PFM), as well as complementary dielectric measurements, the ferroelectric domain structure of single crystals of pure and ruthenium (Ru)-doped 0.9Pb(Zn1/3Nb2/3)O3 (PZN)-0.1PbTiO3 (PT), and Ru/(Zn+Nb+Ti)∼0.002 was analyzed. The coexistence of tetragonal and nontetragonal ferroelectric domains in PZN-PT near the morphotropic phase boundary (MPB) was directly observed via PFM imaging. The incorporation of Ru in the perovskite structure substantially decreases the ferroelectric domain size, thus reducing the polar fraction distributed in the pseudocubic matrix. The polarization and strain hysteresis loops show that Ru doping leads to significant ferroelectric hardening, which is attractive for high-power applications. The local structure and valent state of the incorporated Ru cations were additionally analyzed by electron paramagnetic resonance spectroscopy. Our results demonstrate that doping of tetragonal PZN-PT near MPB is a promising route to design advanced multifunctional single-crystal materials.

Microwave and MM-wave magnetoelectric interactions in ferrite-ferroelectric bilayers

Measurements of the strength of magnetoelectric (ME) interactions at microwave and millimeter-wave frequencies have been carried out on layered ferrite-piezoelectric oxides. An electric field E applied to the composite produces a mechanical deformation, resulting in a field shift δHE or a frequency shift δfE in the resonance. A stripline structure or a cavity resonator was used. The strength of ME coupling is obtained from data on δHE or δfE vs. E. Studies were performed at 1–110 GHz on bilayers of single crystal nickel zinc ferrite or hexagonal ferrites and single crystal lead magnesium niobate-lead titanate, lead zinc niobate-lead titanate or polycrystalline lead zirconium titanate. The coupling strength has been found to be dependent on the nature of piezoelectric phase, magnetic field orientation and volume for both phases. The ME coupling strength is on the order of 1–2 Oe cm/kV (or 3–6 MHz cm/kV) and is an order of magnitude stronger than in polycrystalline ferrite-piezoelectric bilayers. The high frequency ME effect is of importance for dual electric and magnetic field tunable ferrite-piezoelectric devices.

Large converse magnetoelectric coupling in FeCoV/lead zinc niobate-lead titanate heterostructure

Multiferroic behavior was directly verified in a laminated ferroelectric-ferromagnetic heterostructure consisting of a FeCoV thick film (70 μm) and lead zinc niobate-lead titanate (PZN-PT) single crystal. This unique heterostructure demonstrates a significant converse magnetoelectric (CME) effect corresponding to a CME coupling constant of 31 Oe/kV cm−1. It derives from the soft magnetic and magnetostrictive properties (λ=60 ppm) of FeCoV alloy and the superior electromechanical properties (d32=−2800 pC/N) of PZN-PT crystal. The electric field controlled magnetic hysteresis is discussed in terms of a stress-induced anisotropy field model. The theoretical calculation is within 7% of the measured induced field of 240 Oe.

Design and fabrication of PZN-7%PT single crystal high frequency angled needle ultrasound transducers

A high-frequency angled needle ultrasound transducer with an aperture size of 0.4 x 0.56 mm2 was fabricated using a lead zinc niobate-lead titanate (PZN- 7%PT) single crystal as the active piezoelectric material. The single crystal was bonded to a conductive silver particle matching layer and a conductive epoxy backing material through direct contact curing. A parylene outer matching layer was formed by vapor deposition. Angled needle probe configuration was achieved by dicing at 45 degrees to the single crystal poling direction to satisfy a clinical request for blood flow measurement in the posterior portion of the eye. The electrical impedance magnitude and phase of the transducer were 42 Omega and -63 degrees , respectively. The measured center frequency and the fractional bandwidth at -6 dB were 43 MHz and 45%, respectively. The two-way insertion loss was approximately 17 dB. Wire phantom imaging using fabricated PZN-7%PT single crystal transducers was obtained and spatial resolutions were assessed.

Enhanced piezoelectricity around the tetragonal/orthorhombic morphotropic phase boundary in (Na,K)NbO3–ATiO3 solid solutions

The high density perovskite titanates-modified potassium–sodium niobate solid solutions (1−x)(Na0.5K0.5)NbO3−xBaTiO3 and (1−x)(Na0.5K0.5)NbO3−xSrTiO3 have been prepared by the solid state reaction method. The phase diagram summarized from the dielectric property measurement reveals that there exists a tetragonal/orthorhombic morphotropic phase boundary for both the solid solutions. The piezoelectric properties show enhanced behavior at around the tetragonal/orthorhombic morphotropic phase boundary. It is believed that the origin for the high piezoelectric performance (Na,K)NbO3-based lead-free piezoelectric ceramics is the same as that for the lead zinc niobate-lead titanate solid solution.