PMN-PT Crystals Research Articles

Ferroelectric Sb-doped PMN-PT crystal: high electromechanical response with true-remanent polarization and resistive leakage analyses

In this work, pure and Sb-doped PMN-PT (64:36) crystals with pure perovskite phase have been successfully grown using high temperature solutions technique (or, flux technique), in the vicinity of MPB with the size of the crystals varying from 2 × 2 × 1 mm3 to 7 × 5 × 4 mm3. Various properties like dielectric, piezoelectric, ferroelectric and pyroelectric were investigated for the Sb-doped PMN-PT crystals and have been compared to that of pure PMN-PT crystals. In the dielectric studies, the Curie temperature (Tc) for the pure and doped crystal was found to be 190 °C and 155 °C, respectively. Butterfly loops were traced from which a high value of the piezoelectric coefficient for Sb-doped crystal (d33* = 1972 pm/V) was revealed in the voltage range 250–500 V which was fairly greater than that observed for pure PMN-PT crystal (d33* = 1413 pm/V). The Sb-doped PMN-PT crystals displayed excellent saturated ferroelectric hysteresis loops with higher remanent polarization (Pr) value compared to the pure PMN-PT crystals. The doped crystals also displayed good fatigue resistant characteristic indicating the high ferroelectric quality of the crystals. The true or usable polarization (Ptr) component was extracted using the “True-remanent hysteresis” task. The value of Ptr was found to be 41.53 µC/cm2 suggesting lesser contributions (~ 7%) from non-remanent (non-switchable) components of polarization further confirming the good ferroelectric quality of the Sb-PMN-PT crystals. Also, the resistive-leakage characteristic of the doped crystal was analyzed using Time-dependent compensated hysteresis task. These results demonstrate that the Sb-doped PMN-PT crystal possesses excellent properties to achieve a variety of applications.

Direct observation of the domain kinetics during polarization reversal of tetragonal PMN-PT crystal

Lead magnesium niobate-lead titanate (PMN-PT) solid solutions are intensively studied for the last two decades due to their outstanding piezoelectric properties. However, despite the strong interest, there is a lack of studies of domain kinetics and domain structure evolution, which are of great importance for the development of domain engineering in PMN-PT. We present the results of the domain kinetics study during polarization reversal in tetragonal PMN-PT single crystals by in situ optical visualization accompanied by analysis of the switching current. Three types of domain structure evolution have been revealed: (1) formation and growth of macroscopic a-domains, (2) formation of charged domain walls as a result of intersections of macroscopic a-domains, and (3) formation and growth of c-domains. The domain wall motion velocities were estimated. It has been shown by comparison of the switching current and optical one that the main switching current peak is related to the growth of c-domains, whereas the small one is caused by the capacitive input of the charged domain walls. The enhancement of dielectric permittivity by two orders of magnitude due to the appearance of the charged domain walls has been revealed. The difference of forward and reverse polarization reversals was attributed to the clamped switching conditions.

Magnetic properties of L10 FePt thin film influenced by recoverable strains stemmed from the polarization of Pb(Mg1/3Nb2/3)O3–PbTiO3 substrate**Project supported by the National Natural Science Foundation of China (Grant Nos. 11474167, 51701091, and 11504020) and the Start-up Funds of NUIST, China (Grant Nos. 2243141601035 and 2243141601018).

The magnetic properties and magnetization reversible processes of L10 FePt (3 nm)/Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT) heterostructure were investigated by using the phase field model. The simulation results show that the magnetic coercivities and magnetic domains evolution in the L10 FePt thin film are significantly influenced by the compressive strains stemming from the polarization of single crystal PMN–PT substrate under an applied electric field. It is found that the magnetic coercivities increase with increasing of the compressive strain. A large compressive strain is beneficial to aligning the magnetic moments along the out-of-plane direction and to the enhancement of perpendicular magnetic anisotropy. The variations of magnetic energy densities show that when compressive strains are different at the magnetization reversible processes, the magnetic anisotropy energies and the magnetic exchange energies firstly increase and then decrease, the negative demagnetization energy peaks appear at coercivities fields, and the magnetoelastic energies are invariable at large external magnetic field with the energy maximum appearing at coercivities fields. The variations of the magnetoelastic energies bring about the perpendicular magnetic anisotropy so that the magnetoelastic energy is lower at the large external magnetic fields, whereas the appearance of magnetoelastic energy peaks is due to the magnetization-altered direction from the normal direction of the plane of the L10 FePt thin film at coercivities fields.

Optical properties induced and ferroelectric properties enhanced of the PMN-32PT:Ho relaxor ferroelectric crystals

Relaxor ferroelectric crystals PMN-32PT:Ho were prepared by using the flux method. Phase structure and surface morphology of the crystals were performed by using the X-ray diffraction analysis (XRD) and scanning electron microscope (SEM), respectively. A broad dielectric peak in temperature dependent of dielectric spectrum was observed during the phase transition of the PMN-32PT:Ho crystals. The modified Curie-Weiss and Lorentz-type laws were used to describe the dielectric relaxor behavior of the crystals. Optical performances were characterized by using the fluorescence spectrophotometer, Fourier transform infrared spectroscopy (FTIR) and ultraviolet spectrophotometer. Effects of Ho3+ modification on structure, dielectric relaxation, ferroelectric and optical properties of the PMN-32PT crystals were investigated. Ferroelectric properties were improved and the larger coercive field EC was found to be 4.31 kV/cm at room temperature by the Ho modification. Optical performances of the PMN-PT crystals could be induced by the introduction of the Ho ions. The green light of 550 nm and red light of 630 nm were emitted under the excitation at 465 nm. The mechanism of the up-conversion luminescence for as-grown crystals was also discussed.

Patterned nano-domains in PMN-PT single crystals

The domain structure, dielectric, and piezoelectric properties of 0.7 Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT) single crystals with nanocomposite electrode, which includes MnOx semiconductor nanogratings and a Ti/Au conductive layer, were studied in this paper. These artificial MnOx nanogratings can alter the electric field distribution and then enhance the domain density. PMN-PT crystals with Ti/Au-MnOx nanocomposite electrodes showed high piezoelectric constant of 2250 p.m./V and dielectric constant of 5400 at 1 kHz, respectively. Compared to ones with conventional planar electrodes, the piezoelectric and dielectric constants of the samples with nanocomposite electrodes were increased 36.7% and 38.3%, respectively. Piezoresponse force microscopy (PFM) images revealed the domain pattern near the electrode/single crystal interface. A linear domain structure induced by the MnOx nanocomposite electrode was found in the samples with thickness less than 200 μm. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) results showed the diffusion of Mn about 300 nm in depth in PMNPT crystal after heat treatment during MnOx nanocomposite electrode. It is believed that the localized high electric fields induced by fringe effects caused by the nanocomposite electrode can enhance nucleation of new domains, and that diffusion from the patterned Mn layer may also lead to an enhancement in domain wall mobility. Our findings open up a new domain engineering technique for tailoring the dielectric and piezoelectric properties of PMN-PT single crystals.

Investigation of High Frequency Mechanical Vibrations in PMN-32%PT Crystals by Laser Interferometry

Lead magnesium niobate-lead titanate (PMN-PT) single crystal has first been successfully grown in 1990 by the Bridgman method using PbO as a flux. These single crystals have excellent piezoelectric properties. The PMN-PT crystals with different vibration modes may be used for development of novel high efficiency ultrasonic transducers due to high piezoelectric properties.

Phase coexistence and domain configuration in Pb(Mg1/3Nb2/3)O3-0.34PbTiO3 single crystal revealed by synchrotron-based X-ray diffractive three-dimensional reciprocal space mapping and piezoresponse force microscopy

The crystalline phases and domain configuration in the morphotropic phase boundary composition Pb(Mg1/3Nb2/3)O3-0.34PbTiO3 (PMN-0.34PT) single crystal have been investigated by synchrotron-based X-ray 3D Reciprocal Space Mapping (3D-RSM) and Piezoresponse Force Microscopy. The coexistence of tetragonal (T) and monoclinic MC phases in this PMN-0.34PT single crystal is confirmed. The affiliation of each diffraction spot in the 3D-RSM was identified with the assistance of qualitative simulation. Most importantly, the twinning structure between different domains in such a mixed phase PMN-PT crystal is firmly clarified, and the spatial distribution of different twin domains is demonstrated. In addition, the lattice parameters of T and MC phases in PMN-0.34PT single crystal as well as the tilting angles of crystal lattices caused by the interfacial lattice mismatch are determined.

Growth and properties of 4-in. diameter ferroelectric single crystal Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 by the seed-induced modified Bridgman technique

Growth and quality of single crystals are unusually sensitive to the thermal distribution. In the appropriate thermal field ferroelectric single crystal 23Pb(In1/2Nb1/2)O3–44Pb(Mg1/3Nb2/3)O3–33PbTiO3 (abbr. PIN–PMN–PT, or PIMNT), with 105mm in diameter and 150mm in length, is successfully grown by the modified Bridgman technique. This as-grown crystal shows excellent properties (k33~0.92, d33~2200pC/N, Ec~5.7kV/cm, Tc~185°C, Tr/t~120°C; kt~0.60) near morphotropic phase boundary. In order to suppress the compositional segregation and improve the crystal quality, the controllable orientation growth for specific applications is performed successfully using the same oriented seed. For magnetoelectric applications as-grown <110> oriented PIN–PMN–PT crystal demonstrates its high homogeneity (Δε<±6%, Δtanδ<±14%, ΔTr/t<±3%, ΔTc<±3% and Δkt<±2% in a Φ80mm transverse wafer). These results of single crystal PIN–PMN–PT will greatly meet demands of its devices and promote its applications in the future.

Infrared light gated MoS₂ field effect transistor.

Molybdenum disulfide (MoS₂) as a promising 2D material has attracted extensive attentions due to its unique physical, optical and electrical properties. In this work, we demonstrate an infrared (IR) light gated MoS₂ transistor through a device composed of MoS₂ monolayer and a ferroelectric single crystal Pb(Mg(1/3)Nb(2/3))O₃-PbTiO₃ (PMN-PT). With a monolayer MoS₂ onto the top surface of (111) PMN-PT crystal, the drain current of MoS₂ channel can be modulated with infrared illumination and this modulation process is reversible. Thus, the transistor can work as a new kind of IR photodetector with a high IR responsivity of 114%/Wcm⁻². The IR response of MoS₂ transistor is attributed to the polarization change of PMN-PT single crystal induced by the pyroelectric effect which results in a field effect. Our result promises the application of MoS₂ 2D material in infrared optoelectronic devices. Combining with the intrinsic photocurrent feature of MoS₂ in the visible range, the MoS₂ on ferroelectric single crystal may be sensitive to a broadband wavelength of light.

Domain switching and electromechanical properties variation of Pb(In1/2Nb1/2)–Pb(Mg1/3Nb2/3)–PbTiO3 ferroelectric crystals under uniaxial compressive stress

The effect of uniaxial compression stress on the phase/domain pattern and the electromechanical performances were investigated for Pb(In1/2Nb1/2)–Pb(Mg1/3Nb2/3)–PbTiO3 (PIN–PMN–PT) ferroelectric crystals by the polarization/strain vs. electric field and strain vs. uniaxial stress curves measurement. The results showed that (1) uniaxial stress could induce the rotation of polarization from [101]c, [011]c, [−101]c and [0–11]c directions to [110]c, [−110]c, [−1–10]c and [1–10]c directions but no phase transition in orthorhombic (O) phase PIN–PMN–PT crystal; (2) the dielectric and piezoelectric responses of O phase crystal were found to be enhanced by 6.5% and 15% respectively in the region of domain switching due to the increase of free energy instability and polarization mobility induced by uniaxial stress.

Characterization of electrocaloric properties by indirect estimation and direct measurement of temperature–electric field hysteresis loops

The electrocaloric properties of Pb(Zr,Ti)O3(PZT)-based and Ba(Zr,Ti)O3 ceramics and Pb(Mg,Nb)O3–PbTiO3 (PMN–PT) crystals were investigated by the indirect estimation and direct measurement of temperature–electric field (T–E) hysteresis loops. The measured T–E loops showed a similar shape to strain–electric field (s–E) loops. The adiabatic temperature change ΔT due to electrocaloric effects was estimated from the polarization change of these samples. ΔTs of 0.48 and 0.66 K were estimated for the (Pb,La)(Zr,Ti)O3 (PLZT)(9.1/65/35) ceramics and PMN–PT crystals under a field of 30 kV/cm, respectively. The measured temperature changes ΔTs in these samples upon the release of the electric field from 30 kV/cm to zero were 0.39 and 0.36 K, respectively.

Investigation of low-frequency broadband dipole transducer driving by PMN-PT transverse shear mode

A low-frequency broadband dipole transducer with a standard dipole directivity pattern is a crucial factor in the research and development of a sonic logging tool. A new dipole transducer design based on cylindrical shell oscillating is proposed in this paper, in which transverse shear polarization PMN-PT crystal stacks are used to provide a driving force to excite a cylindrical-shell oscillation to generate dipole acoustic field. The resonant frequency of the transducer is decided by the dimensions of crystal stacks. Piezoelectric coefficient d 15 of the PMN-PT crystals can reached 7000 pC/N, which means there is enormous potential in high power transducer design; Several ceramic plates are connected in a series to reduce the resonant frequency of the exciting source and increase the driving amplitude at the same time so as to enhance the radiation power further; several stacks of different sizes are connected in a parallel to broaden the bandwidth. Finite element method is adopted to optimize the structure of transducer. According to the optimized results, a prototype is produced and then tested in anechoic tank. Test results show that the transmitting response is larger than traditional dipole transducer and the directivity pattern is better in the operating frequency range.

Compositional segregation, structural transformation and property-temperature relationship of high-Curie temperature Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 single crystals

Ternary ferroelectric single crystal Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 (PIN–PMN–PT) was grown by the modified Bridgman method. The compositional variation of different regions of the crystals was measured, and the segregation regularity of the crystals was proposed. Variations in the dielectric properties and domain structures of the PIN–PMN–PT single crystals were investigated as a function of temperature and composition, and the phase transformation behavior of the crystals was observed. The PIN–PMN–PT crystals showed high Curie temperatures (T C = 160–210 °C), ferroelectric phase transition temperatures (T R–T up to 132 °C) and coercive fields (E C = 6–8 kV/cm) as well as excellent piezoelectric properties (d 33 up to 2,800 pC/N) and electromechanical coefficients (k 33 > 0.90). As the temperature increased, k 33 values remained relatively constant and d 33 increased gradually prior to ferroelectric phase transformation, and these results reflect the wide temperature usage range of PIN–PMN–PT single crystals. The polarization (P r ) and E C of the crystals showed unique trends during the phase transformation process; high P r and E C values can be maintained prior to depolarization, which indicates that the PIN–PMN–PT single crystals are candidate materials for high-power applications. In summary, PIN–PMN–PT single crystals with ultrahigh electric properties, large coercive fields and excellent thermal stability may potentially be applied in harsh environments.

Application of PMN-32PT Piezoelectric Crystals for Novel Air-coupled Ultrasonic Transducers

Due to very high piezoelectric properties of PMN-PT crystals they may significantly improve performance of air-coupled ultrasonic transducers. For these purpose vibrations of PMN-PT rectangular plates and strips were investigated. An air-coupled ultrasonic transducer and array consisting of 8 single piezoelectric strips were designed. Operation of the transducer was simulated by the finite element method using ANSYS Mechanical APDL Product Launcher software. Spatial distributions of displacements inside piezoelectric elements and matching strip were obtained. Experimental investigations were carried out by the laser Doppler vibrometer Polytec OFV-5000 and the Bruel&Kjaer microphone 4138 with the measurement amplifier NEXUS WH 3219. It was found that performance of the ultrasonic transducer with PMN–32PT crystals was a few times better than of a PZT based ultrasonic transducer.

Temperature-induced and electric-field-induced phase transitions in rhombohedralPb(In1/2Nb1/2)O3−Pb(Mg1/3Nb2/3)O3−PbTiO3ternary single crystals

Temperature and electric field effects on rhombohedral $(R)$ ternary ${\mathrm{Pb}(\mathrm{In}}_{1/2}{\mathrm{Nb}}_{1/2}){\mathrm{O}}_{3}\text{\ensuremath{-}}{\mathrm{Pb}(\mathrm{Mg}}_{1/3}{\mathrm{Nb}}_{2/3}{)\mathrm{O}}_{3}\text{\ensuremath{-}}{\mathrm{PbTiO}}_{3}$ (PIN-PMN-PT) ferroelectric single crystals were comprehensively studied by x-ray diffraction. We have focused on how the individual phase transitions as well as the phase transition sequences depend on thermal and electrical history. Electric field-temperature phase diagrams have been constructed under [001] field-cooling and field-heating conditions. As happens to the $R$ phase of binary PMN-PT crystals [H. Cao, J. F. Li, D. Viehland, and G. Y. Xu, Phys. Rev. B 73, 184110 (2006)], the $R$ phase of the zero-field-cooled (ZFC) state is replaced by a monoclinic A $(M$) phase in the field-cooled (FC) diagram. In particular, reciprocal-space mesh scans demonstrated that the $M$ phase was stable for crystals poled along the [001] crystallographic direction rather than the initial $R$ phase of the ZFC state. Furthermore, an $E$-field-induced phase transformational sequence of $R\ensuremath{\rightarrow}M$\ensuremath{\rightarrow} tetragonal $(T)$ was observed at constant temperature, revealing a gradual increase in the $c$ lattice parameter. These findings demonstrate that the ternary PIN-PMN-PT crystals exhibit common phase transition features with binary PMN-PT and ${\mathrm{Pb}(\mathrm{Zn}}_{1/3}{\mathrm{Nb}}_{2/3}{)\mathrm{O}}_{3}\text{\ensuremath{-}}{\mathrm{PbTiO}}_{3}$ (PZN-PT) ones for compositions in the low PT side of the morphotropic phase boundary.

Growth and Characterization on PMN-PT-Based Single Crystals

Lead magnesium niobate—lead titanate (PMN-PT) single crystals have been successfully commercialized in medical ultrasound imaging. The superior properties of PMN-PT crystals over the legacy piezoelectric ceramics lead zirconate titanate (PZT) enabled ultrasound transducers with enhanced imaging (broad bandwidth and improved sensitivity). To obtain high quality and relatively low cost single crystals for commercial production, PMN-PT single crystals were grown with modified Bridgman method, by which crystals were grown directly from stoichiometric melt without flux. For ultrasound imaging application, [001] crystal growth is essential to provide uniform composition and property within a crystal plate, which is critical for transducer performance. In addition, improvement in crystal growth technique is under development with the goals of improving the composition homogeneity along crystal growth direction and reducing unit cost of crystals. In recent years, PIN-PMN-PT single crystals have been developed with higher de-poling temperature and coercive field to provide improved thermal and electrical stability for transducer application.

Magnetic-field-induced ferroelectric polarization reversal in magnetoelectric composites revealed by piezoresponse force microscopy.

Controlling electric polarization (or magnetization) in multiferroic materials with external magnetic fields (or electric fields) is very important for fundamental physics and spintronic devices. Although there has been some progress on magnetic-field-induced polarization reversal in single-phase multiferroics, such behavior has so far never been realized in composites. Here we show that it is possible to reverse ferroelectric polarization using magnetic fields in a bilayer Terfenol-D/PMN-33%PT composite. We realized this by ferroelectric domain imaging using piezoresponse force microscopy (PFM) under applied magnetic field loading. The internal electric field caused by the magnetoelectric (ME) effect in the PMN-PT crystal is considered as the driving force for the 180° polarization switching, and its existence is verified by switching spectroscopy PFM testing under a series of external magnetic fields. A quantitative method is further suggested to estimate the local ME coefficient based on the switching spectroscopy PFM testing results.

Magnetoelectric effect in FeCo/PMN-PT/FeCo trilayers prepared by electroless deposition of FeCo on PMN-PT crystals with various orientations

The magnetoelectric (ME) effect was studied in the FeCo/PMN-PT/FeCo trilayer composites prepared by electroless deposition of the FeCo layers on the single crystal PMN-PT substrates with various crystal cuts. X-ray diffraction reveals that the orientation of PMN-PT substrate has no effect on the growth of FeCo layer. The structures with PMN-PT crystals of various orientations have different acoustic resonance frequencies. FeCo/PMN-PT/FeCo composites with PMN-PT of 〈001〉L×〈01‾1〉W×〈011〉T crystal cut shows superior ME performance, which is due to the highest piezoelectric module of PMN-PT.

PIN–PMN–PT piezoelectric crystals with increased rhombohedral-to-tetragonal phase transition temperature

In this work, crystal growth and characterization of PIN–PMN–PT (29–59% PIN and 28–35% PT) were conducted to understand how PIN ratio in the PIN–PMN–PT system impacts its phase stability during crystallization. High-quality PIN–PMN–PT crystals with 36% PIN were obtained using the self-seeded Bridgman process, even though the cubic phase In 2 O 3 formed at the very beginning of solidification. The melt became more unstable when the PIN ratio in the PIN–PMN–PT system increased to 49% and above, which affected the composition and quality of the as-grown crystals significantly. By increasing the PIN to 36% in PIN–PMN–PT crystal, the rhombohedral-to-tetragonal phase transition temperatures and the coercive field reached 115–135°C and 4.5~5.6 kV/cm, respectively, that greatly expanded the operation domains compared to PMN–PT crystals.

Crystal growth and property characterization for PIN–PMN–PT ternary piezoelectric crystals

Binary piezoelectric crystal Pb ( Mg 1/3 Nb 2/3) O 3– PbTiO 3 (PMN–PT) has excellent dielectric and piezoelectric properties, which has led to the commercialization for medical ultrasound imaging. Recently, there is a growing demand for piezoelectric crystals with improved thermal and electrical properties. Ternary piezoelectric crystals Pb ( In 1/2 Nb 1/2) O 3– Pb ( Mg 1/3 Nb 2/3) O 3– PbTiO 3 (PIN–PMN–PT) have increased depoling temperature and coercive field than binary PMN–PT. To better understand the ternary crystal system and improve crystal properties, we systematically investigated crystal growth of PIN–PMN–PT with modified Bridgman method. Like PMN–PT, PIN–PMN–PT crystals have excellent piezoelectric properties (e.g., k33 ~ 0.87–0.92, d33 ~ 1000–2200 pm/V ). Higher PIN content leads to ~40°C increase in depoling temperature and more than doubling of coercive field(~7.0 kV/cm). Such improvements are advantageous for applications where high temperature and/or high-drive are needed.