•A novel ternary tetragonal Mn-PIMNT(29/31/40) single crystal has been grown.•The TC reaches 216 °C, 110 °C higher than that of Mn-PMNT(72/28) (TRT ∼ 105 °C).•The εr is as low as 350, 0.5 time than that of Mn-PMNT(72/28)(εr ∼ 640).•The D* of Mn-PIMNT(29/31/40) based pyroelectric detectors is 3 times higher than that of commercial LiTaO3 based detectors.Ferroelectric single crystals Mn-doped 0.29Pb(In1/2Nb1/2)O3-0.31Pb(Mg1/3Nb2/3)O3-0.40PbTiO3 (Mn-PIMNT) have been grown by a modified Bridgman technique. The as-grown ternary tetragonal Mn-PIMNT (29/31/40) single crystals exhibit ultra-high Curie temperature TC of 216 °C, 110 °C higher than that of Mn-PMNT(72/28) single crystals(Td ∼ 105 °C). In addition, the permittivity εr of tetragonal Mn-PIMNT(29/31/40) is 350 at 1 kHz, approximately less than that of Mn-PMNT(72/28)(εr ∼ 640) in half. Moreover, as a core parameter of pyroelectric material, the figure of merits for detectivity (Fd) for Mn-PIMNT(29/31/40) is 23.5 × 10−5Pa−1/2, close to that of Mn-PMNT(72/28)(Fd ∼ 28.5). Finally, outstanding Mn-PIMNT(29/31/40) based pyroelectric detectors were fabricated, of which the specific detectivity (D*) (room temperature, 10 Hz) is up to 1.74 × 109 cmHz1/2/W for current-mode detectors, and 1.15 × 109 cmHz1/2/W for voltage-mode detectors, 3 times higher than that of commercial LiTaO3 based detectors. All of these results make these ternary tetragonal Mn-PIMNT single crystals a promising candidate for infrared detector applications.

Ferroelectric phase transition characteristic and electrical conduction mechanism of the high Curie-point (TC) 0.15Pb(Mg1/3Nb2/3)O3−0.4PbHfO3−0.45PbTiO3 (PMN-PHT) piezoelectric ceramics were studied by the temperature dependent Raman spectra and electrical properties. Sole first-order ferroelectric phase transition is demonstrated by the thermal hysteresis behavior of the temperature dependent dielectric constant and the dramatic drop of the derivative of inverse dielectric constant ξ= d(1/εr)/dT around TC in the PMN-PHT ceramics. The temperature dependent Raman spectroscopy not only provides further evidence for the ferroelectric to paraelectric phase transition appearing around TC in the PMN-PHT ceramics, but also reveals the successive phase symmetry changes of the polar nanoregions (PNRs), in which apparent anomalies appear in the Raman peaks' wavenumber, wavenumber distance, intensity, intensity ratio, and line width of some selected Raman modes upon heating. Typical sole cole-cole circle is obtained for the PMN-PHT ceramics in the temperature range of 440–560 °C, based on which the activation energy (Ea) of the electrical conduction is calculated being ~1.2 eV. Such low value of Ea indicates that the oxygen vacancies formed in the PHT-PMN ceramics induced by the evaporation of Pb during the sintering process dominate the high-temperature extrinsic electrical conduction.

•High sintering capability Er3+-doped Na0.5Bi0.5TiO3 (NBT) nano particles were prepared by a simple hydrothermal method.•The Er3+-doped NBT ceramics prepared via the hydrothermal method exhibit pure perovskite structure and high densification.•The Er3+-doped NBT ceramics exhibit excellent upconversion and downconversion luminescence properties.Er3+-doped Na0.5Bi0.5TiO3 (Er-doped NBT) ceramics were prepared via a hydrothermal method. High sintering active Er-doped NBT nano cubic particles with perovskite structure were synthesized at hydrothermal condition of 200 °C for 24 h in 12 M NaOH solution, which were self-assembled via in situ crystallization mechanism by the initially as-grown nanowires. The Er-doped NBT ceramics sintered at 1100 °C for 2 h exhibit pure rhombohedral perovskite structure, high densification and rather homogenous microstructure morphology. Under 488 nm light excitation, the strong green emission peaks centering at 530 nm and 550 nm and the weak red emission peaks locating at 665 nm and 735 nm are excited, which can be attributed to the 2H11/2, 4S3/2, 4F9/2 and 4I9/2 → 4I15/2 transitions, respectively. The maximum emission intensity is obtained when the Er doping content reaches 1.0 mol%. A strong upconversion emission peak centering around 550 nm in green light range is excited under 800 nm light excitation, which is correlated with the 4S3/2 → 4I15/2 transition.

•The PIMNT/epoxy 2-2 composite flake is prepared by a novel non-transfer process.•The stripe electrodes overlapping IDEs make the composite flake well polarized.•The device can endure a small bending radius of 2.2 cm due to the sandwich structure.•Bulk PIMNT crystal contributes to high output of the device (54.2 V/105 μW).•The wearable device harvests biomechanical energy of knees motion successfully.Unlike the nano-generators whose piezoelectric materials in forms of particles, fibers and thin film, we present a sandwich structure flexible energy harvester using a high performance bulk form PIMNT/epoxy 2-2 composite flake (epoxy volume ratio of 20%). The device consists of a polyethylene terephthalate (PET) substrate, a PIN-PMN-PT single crystal/epoxy 2-2 composite flake (a thickness of 50 mm), an interdigital electrodes (IDEs) film and a PET cover, which is flexible enough to harvest energy from large deformation biomechanical movements. A theoretical analysis shows that the sandwich structure with composite in the middle layer contributes to the flexibility of the device and high performance bulk PIN-PMN-PT results in its high electrical output. Electrical properties of the device under different strains (bending radius), strain rates, electrode gaps and load resistances are studied systematically. Experimental results show that the device can withstand a small bending radius of 2.2 cm, where an open-circuit of 54.2 V and extrapolation current of 6.7 μA were acquired across a device area of 480 mm2. The instantaneous power reach as high as 105 μW and can maintain its performance after 40000 bending-unbending cycles. We have also used the device to harvest the mechanical energy from motions of human knees and light up 12 red LEDs successfully. High flexibility and excellent electrical output demonstrate the promise of the device in biomechanical motions energy harvesting for self-powered wireless and portable low-power electronics.

Domain configuration evolution with temperature of the unpoled [001]C-oriented 0.32Pb(In1/2Nb1/2)O3–0.345Pb(Mg1/3Nb2/3)O3–0.335PbTiO3 (0.32PIN–0.345PMN–0.335PT) single crystals was studied by the polarized light microscopy (PLM). The optical observation of the domain structures reveals the coexistence of polymorphic ferroelectric phases with mainly ferroelectric monoclinic phase at room temperature and the irreversible domain evolution upon thermal cycling, which induce the high piezoelectric response in such relaxor-based ferroelectric single crystals with the morphotropic phase boundary compositions combined with polarization rotation. The temperature dependent domain evolution and dielectric behavior demonstrate the successive temperature-induced second-order ferroelectric M phase to ferroelectric tetragonal (T) phase (FEM–FET) and first-order ferroelectric T phase to paraelectric cubic (C) phase (FET–PC) ferroelectric phase transitions in the unpoled 0.32PIN–0.345PMN–0.335PT single crystals. Two dielectric loss anomalies were detected around the dielectric anomaly below 100 °C in the poled 0.32PIN–0.345PMN–0.335PT single crystals, indicating that the FEM–FET phase transition can be correlated with two different ferroelectric phase transitions, one is MA–MC, and the other is MC–T phase transition. The FEM–FET phase transition was confirmed further by the energy density measurement. The temperature dependent piezoelectric properties proved that the working temperature of the 0.32PIN–0.345PMN–0.335PT single crystals can reach 130 °C, higher around 50 °C than the Pb(Mg1/3Nb2/3)O3–PbTiO3 single crystals, indicating their promising applications in transducers used at elevated temperatures.

In situ observations of the phase symmetry and domain evolution of (K0.25Na0.75)NbO3 single crystals under bipolar electric fields have been performed for both pseudocubic (110) and (001) orientations using polarized light microscopy and X-ray diffraction. The macroscopic symmetry was identified to be a monoclinic C type phase with the spontaneous polarization direction close to <054>. The electric field-driven domain morphology and evolution model were also presented. It was found that, under an antiparallel electric field, the approximately 180° domain switching process in a pseudocubic (101) sample consists of three steps: two ~60° domain switching and a ~90° domain switching, and the ~90° domain switching process in the pseudocubic (001) sample is composed of two ~60° switching steps.

A series of (Na0.5Bi0.5)TiO3–PbTiO3 (NBT–PT) single crystals with compositions near the morphotropic phase boundary (MPB) region were grown by the modified Bridgman technique. The dependence of structure on composition was measured, and the MPB region of the NBT–PT system was confirmed. The dielectric properties of the NBT–PT single crystals were investigated, and the phase transition behaviour of the NBT–PT single crystals during heating was examined. With increasing addition of PT, the coercive field of the NBT–PT crystals decreased to levels much lower than that of the pure NBT system; such a change allowed easy poling of the NBT–PT crystals and the resultant piezoelectric properties were significantly enhanced. The electromechanical coupling factor of the crystals showed relatively constant thermal stability at the depolarization temperature (Td). Finally, studies of the domain evolution of NBT–0.09PT showed the disappearance of domains at the Td, which indicates that phase transition at the Td is related to changes in domain structures.

•Large size NBT–xKBT (x=5%, 8% and 12%) single crystals were grown using a TSSG method.•The dielectric, ferroelectric and piezoelectric properties of the as-grown crystals were characterized systematically.•The values of d33 and kt of NBT-12KBT reach to 208 pC/N and 0.53, respectively.•The temperature and composition dependent crystal structure was studied by in-situ X-ray diffraction and Raman spectroscopy..Dielectric, ferroelectric and piezoelectric properties of lead-free Na1/2Bi1/2TiO3–xK1/2Bi1/2TiO3 (NBT–xKBT) ferroelectric single crystals were characterized systematically. With increasing KBT concentration, the remanent polarization and coercive electric field decrease, while the piezoelectric constant and the electromechanical coupling coefficient increase. The evolution of average and local structures as a function of temperature and composition was investigated using in-situ X-ray diffraction and Raman spectroscopy. The structure/property relationship of NBT–xKBT single crystals was discussed in detail.

The clamped–clamped beam has attracted increasing attention in the area of piezoelectric energy harvesting and transducer. In this paper, we present the theoretical models of clamped–clamped piezoelectric unimorph and bimorph beams with a quasi-static force in the middle. Based on the models, numerical studies are carried out to compare the generated charge, open-circuit voltage and generated energy of the piezoelectric beams under different condition. The simulation results demonstrate that the output performance of the beams are depended on the bonding position and electromechanical properties of the piezoelectric layer, and the length ratio, thickness ratio and the Young’s modulus ratio (YMR) of the piezoelectric layer and substrate. Specifically, the unimorph and bimorph beams share the same optimal length ratio while their optimal width ratio and thickness ratio are different. The YMR imposes a great impact on the performance of the beam both in the unimorph and bimorph cases. As a generalization, the models are not only suitable for the beam with a non-uniform cross-section but also applicable for the beam with uniform cross-section. The analyses can be used to improve the performance of the clamped–clamped beam working as an energy harvester and transducer.

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 (TC = 160–210 °C), ferroelectric phase transition temperatures (TR–T up to 132 °C) and coercive fields (EC = 6–8 kV/cm) as well as excellent piezoelectric properties (d33 up to 2,800 pC/N) and electromechanical coefficients (k33 > 0.90). As the temperature increased, k33 values remained relatively constant and d33 increased gradually prior to ferroelectric phase transformation, and these results reflect the wide temperature usage range of PIN–PMN–PT single crystals. The polarization (Pr) and EC of the crystals showed unique trends during the phase transformation process; high Pr and EC 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.

•Distributed electrode structure of sensitive element was designed for PMNT based pyroelectric infrared detector.•Different electrode distances have been investigated for this structure.•Under the optimal electrode distance of 0.5 mm, the figure of merit for detectivity is up to 39.9 × 10−5 Pa−1/2.•Three forms of figure of merit for detectivity were derived based on the different mechanisms.•The responsivity and specific detectivity of the proposed structure are 3.6 and 1.4 times higher than that of the conventional faced electrode structure.A distributed electrode structure of sensitive element based on Mn-doped Pb(Mg1/3Nb2/3)O3-0.29PbTiO3 single crystals for high-end pyroelectric infrared detectors has been proposed, demonstrating a notably superior pyroelectric response. Under the optimal electrode distance of 0.5 mm, the figure of merit for detectivity is up to 39.9 × 10−5 Pa−1/2. An ultrahigh responsivity of 864 V/W and specific detectivity of 1.49 × 109 cm Hz1/2/W at 10 Hz are observed, approximately 3.6 and 1.4 times higher, respectively, than that of the conventional faced electrode structure. The enhanced responsivity and specific detectivity of the distributed electrode structure will make PMNT based detectors with voltage mode promising in practical use of sensors.

•Highly performed ferroelectric single crystal PIMNT has been used.•PIMNT/epoxy 2–2 composite has been designed and fabricated.•Excellent piezoelectric properties have been achieved.•Array transducer with broad bandwidth (127.7% @-6 dB) has been designed and fabricated.In order to improve the applicability of Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 (PIN–PMN–PT) single crystal and make full use of relaxor ferroelectric single crystal based array transducer on high frequency, PIN–PMN–PT/epoxy 2–2 composite with the width-to-height ratio G of 0.5 in single crystal beam was prepared by a dice-and-fill method. Excellent properties for the fabrication of ultrasonic transducer has been achieved, where ultrahigh thickness electromechanical coupling coefficient (kt), ultrahigh effective electromechanical coupling coefficient (keff), relatively high piezoelectric constant (d33), and low acoustic impedance (Z) are 86%, 88.4%, 1200 pC/N and 21 MRayls, respectively. Based on the improved flexibility of as-prepared PIN–PMN–PT/epoxy 2–2 composite, a 12-element array transducer with the center frequency of 10 MHz has been designed, fabricated and characterized. The high frequency array transducer has achieved an ultra-broad bandwidth (@-6 dB) of 127.7%. It is worth mentioning that all 12 elements in the array work very well. The array transducer based on PIN–PMN–PT/epoxy composite exhibits excellent uniformity, confirming that the relaxor ferroelectric single crystal based 2–2 composite can be used to develop high-performance array transducer in the field of high frequency application.

•We fabricate a novel Metglas/PIMNT L–L mode magnetoelectric composite.•The distributed capacitance depend on the number of insulating Kapton layers.•Magnetoelectric voltage coefficients is 17 V/Oe at quasi-static frequency.•Estimated noise equivalent magnetic induction is as low as 8.6 pT/Hz1/2@1 Hz.•Output power reaches 29.2 mW/Oe2 for magnetic field energy harvesting.In this paper, a magnetoelectric laminate composite based on length magnetized Metglas and length-polarized ternary 0.35Pb(In1/2Nb1/2)O3–0.35Pb(Mg1/3Nb2/3)O3–0.30PbTiO3 (PIMNT) single crystal has been presented. This Metglas/PIMNT L–L mode composite exhibits ultrahigh magnetoelectric voltage coefficients of ∼17 V/Oe at quasi-static frequency and of ∼147 V/Oe at resonance frequency, which are much larger than other magnetoelectric composites reported so far. Analysis of magnetic field sensitivity indicates that the estimated noise equivalent magnetic induction of the proposed composite is as low as 8.6 pT/Hz1/2@1 Hz. Due to its giant magnetoelectric voltage coefficients, the maximum magnetic-field-energy-harvesting output power reaches 29.2 mW/Oe2, which is about 3.65 times than that of previously reported Metglas/PMNT multi-push–pull mode composite. Accordingly, the proposed Metglas/PIMNT L–L mode composite shows promising applications in magnetic field detection sensors as well as transducers for magnetic field energy harvesting.

Single crystals of x at% Fe + 0.95(Na1/2Bi1/2)TiO3-0.05BaTiO3 (x%-Fe:NBBT5, x = 0.1, 0.2 and 0.5) with ultrahigh ferroelectric response were developed by introducing defect associations. The very large field-induced bipolar and unipolar strains, i.e., Smax ∼ 1.1%, εmax/Emax ∼ 1300 pm V−1, d33 ∼ 600 pC N−1 and permittivity tunability ∼120%, demonstrate that these crystals are promising candidates as lead-free ferroelectrics. The presence of ferromagnetic properties further provides their new application potential as multiferroic materials. The defect chemistry and domain structure were studied systematically. The effects of microscopic defect functional centers on macroscopic properties were discussed in detail.

Lead-free (K0.25Na0.75)NbO3 (KNN25/75) single crystals with dimensions of Ø30 × 10 mm were successfully grown by a top seeded solution growth technique (TSSG). The X-ray diffraction pattern shows that the as-grown crystals possess an orthorhombic perovskite structure. The concentrations of K, Na, and Nb elements in the as-grown crystal were measured by X-ray fluorescence analysis. The dielectric, ferroelectric and piezoelectric properties of KNN25/75 crystals with different orientations, i.e., pseudocubic (100) and (110) ((100)pc and (110)pc), were investigated. A higher piezoelectric constant d33 ~ 145 pC N−1 and electromechanical coupling coefficient kt ~ 69% were observed along the (100)pc orientation compared with d33 ~ 70 pC N−1 and kt ~ 51% along (110)pc. However, when a bipolar electric field was applied, a two times higher strain value can be achieved in crystals oriented along (110)pc than along (100)pc. These orientation dependent physical properties can be explained in the framework of domain engineering and the switching effect.

Giant bipolar and unipolar strains i.e. Smax > 0.5%, εmax/Emax > 1000 pm V–1 have been observed in Mn-doped Na0.5Bi0.5TiO3–6BaTiO3 single crystals after being annealed. Temperature-dependent impedance spectra were studied and activation energies of oxygen vacancies were calculated accordingly. The two different binding energies present in X-ray photoelectron spectra for Na and Bi were assigned to different coordinate environments. However, titanium exhibits only one oxidation state (e.g. Ti4+). The site occupation and valence fluctuation of Mn were characterized by electric paramagnetic resonance spectra.

•High Tc and high pyroelectric coefficient are obtained by component regulatory.•Mn-doping contributes to depress dielectric loss to 0.0003.•Dielectric and pyroelectric performances depend on the number of oxygen vacancies.•Oxygen-annealing promotes detectivity figure of merit up to 34.1 × 10−5 Pa−1/2.•P–E loops describe domain switching with frequency of applied electric field.Mn-doped 0.15Pb(In1/2Nb1/2)O3–0.55Pb(Mg1/3Nb2/3)O3–0.30PbTiO3 single crystals were grown by modified Bridgman technique. High dielectric peak temperature of 161 °C, low dielectric loss of 0.03% and enhanced pyroelectric coefficient of 10.1 × 10−4 C/m2 K are observed. Effects of oxygen vacancies related to annealing atmosphere have been investigated to explain enhanced dielectric and pyroelectric properties. Detectivity figure of merit of 34.1 × 10−5 Pa−1/2 is achieved for oxygen-annealed crystals, which is the highest value among reported PIMNT crystals. Two different linear relationships between the coercive field and frequency are observed to obey Merz’s law, which reveals the domain and polarization switching mechanism.

Piezoelectric energy harvesting is widely used to scavenge vibration energy in the environment. For some vibration sources with fixed frequency, cantilevered harvester can generate the energy effectively, so the optimization theory for cantilevered harvester in such an application is needed. In this article, we present the theoretical and experimental studies of the cantilevered piezoelectric energy harvester with a fixed resonance frequency. An analytical model based on energy method is used to estimate the open-circuit voltage and generated energy. Considering that the harvester may be subjected to the static force or steady-state sinusoidal vibration excitation, static and dynamic analysis is performed for device structure to achieve efficient energy. In the analysis, the effects of geometrical dimension on the energy harvesting performance are discussed comprehensively. Eventually, a prototype is designed and fabricated using (1−x)Pb(Mg1/3Nb2/3)O3−xPbTiO3 (PMN-PT) single crystal with ultrahigh piezoelectric properties and coupling factor. Performances of the cantilever with different clamped length are evaluated under sinusoidal vibration excitation, proving the good consistency between experimental results and theoretical prediction. The established analysis can provide useful guidelines for the structure design of cantilevered piezoelectric energy harvester with a fixed resonance frequency.

•We test the frequency dependence of the ME charge coefficients and the noise floor of the sensor.•We examine the ability to reject vibrational noises.•Giant ME effect has been found, the ME voltage coefficient reaches 890 pC/Oe at low frequencies with a low noise floor of 32 pT/Hz1/2 at 1 Hz, which was very close to the estimated value (27 pT/Hz1/2).•The results show an excellent ability to attenuate the vibrational noise by 91%.Giant ME effects in laminates have been investigated for highly sensitive low frequency magnetic field sensors. It has been shown in recent years that one of the biggest obstacles for magnetoelectric (ME) sensors achieving high sensitivity at low frequency is the vibrational noise introduced via piezoelectric effect.This work demonstrates a novel differential technique which has the ability to reject the vibrational noise in a multilayer structured ME sensor. It exhibits an excellent ME effect with a low equivalent magnetic noise floor of 32 pT/Hz1/2 at 1 Hz and 3 pT/Hz1/2 at 10 Hz, which was very close to the predicted value (27 pT/Hz1/2 at 1 Hz and 2.9 pT/Hz1/2 at 10 Hz). With respect to the ability to reject the vibrational noise, the external vibrational noise was incredibly attenuated by 91%. These unique properties of the multilayer structured sensor offer potential applications as a precise and sensitive magnetic field detector.

Measured results of magnetoelectric (ME) and converse magnetoelectric (CME) effects of TbxDy1−xFe2−y/Pb(Mg1/3Nb2/3)(1−x)TixO3/TbxDy1−xFe2−y (TD/PMNT/TD) and PMNT/TD/PMNT laminated composites are presented. ME effect was determined by measuring laminate voltage output under a Helmholtz-generated AC field biased by a DC field (0–1 kOe) (1 Oe = 79.58 A/m). The CME effect was measured by recording the voltage induced in a solenoid encompassing the ME sample while exposed to a DC bias field and PMNT layer driven by a 10 V AC source. The ME and CME responses in the two laminated structure are linear. The highest values of ME coefficients in TD/PMNT/TD and PMNT/TD/PMNT composites are 384 mV/Oe and 158 mV/Oe, respectively, while the highest values of CME coefficients in the two composites are 118 mG/V and 162 mG/V (1 G=10−4 T), respectively.

•A 15 μm sensitive chip with ultralow dielectric loss of 0.005% at 1 kHz was achieved.•The figure of merit for detectivity was up to 92.6 × 10−5 Pa−1/2.•The suspending architecture was obtained using 3D-Printing technology.•The RV and D* are 669,811 V/W and 3.32 × 109 cm Hz1/2/W at 10 Hz, respectively.•This suspending architecture can largely inhibit the microphonic effect.A sensitive chip with ultralow dielectric loss based on Mn doped PMNT (71/29) has been proposed for high-end pyroelectric devices. The dielectric loss at 1 kHz is 0.005%, one order lower than the minimum value reported so far. The detective figure of merit (Fd) is up to 92.6 × 10−5 Pa−1/2 at 1 kHz and 53.5 × 10−5 Pa−1/2 at 10 Hz, respectively. In addition, an inverted pyramid suspending architecture for supporting the sensitive chip has been designed and manufactured by 3D printing technology. The combination of this sensitive chip and the proposed suspending architecture largely enhances the performance of the pyroelectric detectors. The responsivity and specific detectivity are 669,811 V/W and 3.32 × 109 cm Hz1/2/W at 10 Hz, respectively, 1.9 times and 1.5 times higher than those of the highest values in literature. Furthermore, the microphonic effect can be largely inhibited according to the theoretical and experimental analysis. This architecture will have promising applications in high-end and stable pyroelectric infrared detectors.

•We present fabrications and properties of the L-T and L-T mode ME composites.•The equivalent magnetic noise levels at high frequency are measured.•The equivalent magnetic noise of the L-W mode sensor is 0.78 pT/Hz1/2 at 30 kHz.•The dominated noise source can be confirmed from OPA at high frequency range.In this paper, we investigate the responsivities and output voltage noise power spectral densities of magnetoelectric (ME) laminate sensors, consisting of length magnetized Terfenol-D alloys and transverse/width poled Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMNT) crystals (i.e. L-T mode and L-W mode respectively), which are directly integrated with custom-build low noise charge amplifier circuits. Both the theoretical analyses and experimental results prove that the L-W mode sensor with the optimized polarized direction of the PMNT plate possesses lower magnetic detection limit at the interested high frequency range of 10 kHz≤f≤50 kHz. The equivalent magnetic noise (EMN) of the L-W mode sensor is 0.78 pT/Hz1/2 at 30 kHz, which is about 1.7 times lower than the 1.35 pT/Hz1/2 for conventional L-T mode sensor. Furthermore, an effective method of using operational amplifiers with low equivalent input noise voltage and employing ME laminate composites with high voltage coefficient to reduce the EMNs of the ME laminate sensors at high frequency range has been established.

•A new ferroelectric single crystals PLN–PMN–PT were grown for the first time.•Good compositional uniformity was shown in PLN–PMN–PT crystals.•High Curie temperature and large coercive field were displayed in PLN–PMN–PT crystals.•Excellent electrical properties were maintained at high temperatures in PLN–PMN–PT crystals.A new relaxor-based ferroelectric ternary system Pb(Lu1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 (PLN–PMN–PT), with a combination of a high-Curie temperature system Pb(Lu1/2Nb1/2)O3–PbTiO3 (PLN–PT) and a high piezoelectricity system Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT), was investigated in this paper. Single crystal PLN–PMN–PT with dimensions of Φ20×45 mm3 was grown successfully by the modified Bridgman technique for the first time. The studies of structure and composition of the as-grown crystal showed structural consistency but compositional deviation along the growth direction. The 〈0 0 1〉-oriented wafers of the PLN–PMN–PT single crystal showed excellent electrical properties at room temperature: ε33~4500, tanδ~0.5%, d33~2300 pC/N. The crystal was found to exhibit high Curie temperature (TC~176°C), rhombohedral–tetragonal phase transition temperature (TRT~108 °C) and coercive field (EC~8.1 kV/cm), superior to those of PMN–0.3PT single crystal. Studies of temperature dependence ferroelectric properties showed that high values of k33 and d33 could be maintained up to the TRT. These results showed that PLN–PMN–PT piezoelectric single crystal has a higher Curie temperature and coercive field with excellent electrical properties, making the crystal a promising candidate for high-power transducer applications in a broad temperature range.

Single crystals of x at% Fe + 0.95(Na1/2Bi1/2)TiO3-0.05BaTiO3 (x%-Fe:NBBT5, x = 0.1, 0.2 and 0.5) with ultrahigh ferroelectric response were developed by introducing defect associations. The very large field-induced bipolar and unipolar strains, i.e., Smax ∼ 1.1%, εmax/Emax ∼ 1300 pm V−1, d33 ∼ 600 pC N−1 and permittivity tunability ∼120%, demonstrate that these crystals are promising candidates as lead-free ferroelectrics. The presence of ferromagnetic properties further provides their new application potential as multiferroic materials. The defect chemistry and domain structure were studied systematically. The effects of microscopic defect functional centers on macroscopic properties were discussed in detail.