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The outstanding pulse energy-storage BLLMT–NN ceramics with conspicuous frequency and temperature stability and anti-fatigue feature were achieved via multiscale modification.

Single crystals of LiCaAlF6:Eu and LiCaAlF6:Ce with a diameter of 25.4 mm were grown by the Bridgman method in a nonvacuum atmosphere. The as-grown crystals are highly transparent and crack- and in...

(Ba0.85Ca0.15) (Hf0.10Ti0.90)O3 (BCHT) ceramics were prepared via the powder injection molding process using paraffin as simple injection binder. Rather pure perovskite BCHT ceramics are obtained sintered at different temperatures, and complex multi-ferroelectric phases coexistence is confirmed by XRD measurement. Although the relative density is around 90%, well densified microstructural morphology is obtained without detectable gas pores. Curie temperature (TC) and dielectric constant maximum (em) change irregularly with sintering temperature, and the BCHT ceramics present complex ferroelectric nature. All the ceramics show easy polarization characteristic, and the 1540 °C sintered BCHT ceramics present the largest piezoelectric constant d33 = 554.6 pC/N. Thickness mode ultrasonic transducer was fabricated based on the 1450 °C sintered BCHT ceramics, where the bandwidth @-6 dB (BW-6 dB) is 56.25% and sensitivity is −31.867 dB. PiezoCAD software simulation data present good agreement with the experimental results, showing promising applications for non-destructive testing using the BCHT lead-free ceramics.

Piezoelectric and pyroelectric properties as well as strain behavior of 0.5 mol% Mn-doped 0.36Pb(In1/2Nb1/2)O3-0.36Pb(Mg1/3Nb2/3)O3-0.28PbTiO3 (Mn-PIMNT) ceramics were studied. High piezoelectric coefficient of d33 = 235 pC/N, planar electromechanical coupling factor of kp = 43.1% and the high-power Figure of Merit (FOM = 60160 pC/N) were achieved in Mn-PIMNT ceramics. Furthermore, the ceramics exhibited high pyroelectric coefficient of p = 4.8×10-4 Cm-2K-1, figures of merit for the current responsivity of Fi = 1.92×10-10 mV-1, the voltage responsivity of Fv = 0.028 m2C-1, and the detectivity of Fd = 2.317×10-5 Pa-1/2 at room temperature. The excellent piezoelectric and pyroelectric properties together with high ferroelectric rhombohedral to tetragonal phase transition temperature of Trt = 146 ℃ and ferroelectric tetragonal to cubic phase transition temperature of TC = 188 ℃ make the Mn-PIMNT ceramics suitable for high-temperature piezoelectric and pyroelectric devices.

Optical properties of -oriented pure (K0.4Na0.6)NbO3 (KNN) and 0.5 wt% Mn-doped KNN (Mn-KNN) single crystals were studied. The refractive indices (n) of both crystals exhibited a normal dispersion behavior in the wavelength range of 300−1100 nm. The modified Sellmeier dispersion equations for n were obtained by least-squares fit. In addition, Sellmeier coefficients were determined by single-oscillator dispersion relation, which related to energy band structures of crystals. Compared with KNN, a decrease about 10 % in transmittance (over 350 nm) was observed in Mn-KNN due to the losses resulting from the increase of domain wall density. Furthermore, a 20 nm blue-shift in the absorption edge was observed for Mn-KNN. Based on Tauc equation, the band gap energies of 3.26 and 3.42 eV were obtained for KNN and Mn-KNN, respectively. The increase of band gap energy in Mn-KNN was attributed to the distortion of BO6 octahedron building block caused by Mn2+ occupying the B-site.

In this paper, the 0.15Pb(Mg1/3Nb2/3)O3-0.38PbHfO3-0.47PbTiO3 ternary piezoelectric ceramic fabricated by the partial oxalate method that exhibits superior electrical properties (d33 = 447 pC/N and kt = 56.9%) and excellent thermal stability of the piezoelectric properties below TC was studied. The newly discovered piezoelectric ceramic had a high Curie temperature (Tm = 297 °C), this feature was used to fabricate a novel single-element ultrasonic transducer whose center frequency was 2.15 MHz, with a −6 dB bandwidth of up to 79.07%, and a sensitivity that reached −31.75 dB. The result of the experiment agreed well with that of PiezoCAD software based on the KLM model. This transducer's outstanding thermal stability below TC can be widely used in non-destructive evaluation. At the same time, we measured the sound field distribution of the ultrasonic transducer. The focal length was measured approximately 47 mm. An obvious main lobe was clearly seen from the z–x scan. The power was measured as 17.98 mW; the beam width of –3dB was 3.5 × 3.6 mm; and the area was 9.83 mm2 according to the FDA and IEC standards.

The electrochemical oxygen reduction reaction ORR offers a most promising and efficient route to produce hydrogen peroxide H2O2 , yet the lack of cost effective and high performance electrocatalysts have restricted its practical application. Herein, an entropy enhancement strategy has been employed to enable the low cost perovskite oxide to effectively catalyze the electrosynthesis of H2O2. The optimized Pb NiWMnNbZrTi 1 6O3 ceramic is available on a kilogram scale and displays commendable ORR activity in alkaline media with high selectivity over 91 amp; 8201; across the wide potential range for H2O2 including an outstanding degradation property for organic dyes through the Fenton process. The exceptional performance of this perovskite oxide is attributed to the entropy stabilization induced polymorphic transformation assuring the robust structural stability, decreased charge mobility as well as synergistic catalytic effects which we confirm using advanced in situ Raman, transient photovoltage, Rietveld refinement as well as finite elemental analysis

Wearable energy harvesters and sensors have recently attracted significant attention with the rapid development of artificial intelligence and the Internet of Things (IoT). Compared to high-output bulk materials, these wearable devices are mainly fabricated by thin-film-based materials that limit their application. Therefore, the enhancement of output voltage and power for these devices has recently become an urgent topic. In this paper, the lead-free bismuth titanate-barium titanate (0.93(Na0.5Bi0.5)TiO3-0.07BaTiO3(BNBT)) nanoparticles and nanofibers were embedded into the PVDF nanofibers. They produced high inorganic electrical voltage coefficients, high electromechanical coupling coefficients, and environmentally friendly properties that enhance the electromechanical performance of pure PVDF nanofibers, and they are all the critical requirements for modern flexible pressure sensors. In detail, PVDF and PVDF-based composites nanofibers were prepared by electrospinning, and different flexible sandwich composite devices were fabricated by the PDMS encapsulation method. As a result, the six-time enhancement maximum output voltage was obtained in a PVDF-BNBT (fiber)-based composite sensor compared to the pure PVDF one. Our results indicate that the output voltage of the pressure sensors has been significantly enhanced, and the development gate is enabled by analyzing the related physical process and influence mechanism.

A multifunctional material 0.65Ba0.955Yb0.025Er0.005TiO3–0.35CoFe2O4, owning superior piezoelectric, photoluminescence and magnetostrictive effects, was prepared via the conventional solid-state ceramic fabrication process. The ferroelectric, piezoelectric, dielectric, photoluminescence, as well as magnetic properties were characterized. Furthermore, in-situ magneto-electric, electro-photoluminescence and magneto-photoluminescence coupling effects were studied. A relatively larger magneto-electric coupling coefficient αE33 was determined to be 11 mV/Oe•cm@1 kHz, while the reversible electric and magnetic modulation ratio of integral intensity of green emission reached 16%@15 kV/cm and 2%@2 kOe, respectively. The underlying mechanism was discussed by PFM results, and the present work provides an alternative material to design devices with multiple functions.

The propagation properties of surface acoustic wave (SAW) on the Na0.5Bi0.5TiO3–BaTiO3 (NBBT) substrate with different crystal cuts were theoretically analyzed by Finite Element Method (FEM). The calculated results, for the NBBT with the optimized electrode type and thickness, indicate the existence of Rayleigh and Sezawa modes with high electromechanical coupling factor K2 ~18% and ~6.8% respectively, which are considerably higher than that of the conventional lithium niobate (LiNbO3) single crystal for SAW applications. The research provides a comprehensive understanding of the SAW propagation characteristics of lead-free NBBT, and explores the promising applications of NBBT in wideband SAW devices.

Due to the urgent demands for high-Curie temperature (TC/Tm) piezoelectric materials in geothermal exploration, aerospace and related fields, high-TC/Tm ferroelectrics have attracted booming research attention. The high-Tm 0.25Bi(Ni1/2Ti1/2)O3-0.75 Pb(Zr1/2Ti1/2)O3 (0.25BNT-0.75PZT) ceramics were prepared by solid-state sintering method and via partial oxalate route, where the 0.25BNT-0.75PZT ceramics prepared via the partial oxalate route exhibit better electrical properties (Tm = 232 °C (10 kHz), em = 10963, Pr = 26.14 μC/cm2, Ec = 15.61 kV/cm, d33 = 521 pC/N, d33* = 553.3 pm/V, Kp = 47.1%, and Qm = 21.6). The nano-scale domain configuration of the ceramics was revealed by piezoelectric force microscopy (PFM), and the relationship between the micro-structure and macro-electrical properties was analyzed. The ferroelectric phase transition mechanism was studied by temperature dependent Raman spectroscopy. The reduction of energy barrier of lattice distortion and polarization deflection is caused by nanometer-sized domain structure, low symmetric polar nano-regions and/or coexistence of multi-ferroelectric phases, contributing to the excellent electrical properties of the 0.25BNT-0.75PZT ceramics prepared via the partial oxalate route.

Multifunctional perovskite oxides [(Ba0.85Ca0.15)1-xEux](Ti0.9Hf0.1)O3 (Eu-BCTH) were prepared by the solid-state reaction method, and the effects of Eu doping on structure, density, and performance were studied. The Eu-BCTH ceramics sintered at 1450 °C for 3 h exhibit a near-pure perovskite structure accompanied by high relative density and densified microstructure morphology. The Eu-doped BCTH ceramics present complicated dielectric behaviour, that is, normal ferroelectrics accompanied by slight diffusive ferroelectric phase transition characteristics. Excellent ferroelectricity and piezoelectricity can be obtained in the Eu-doped BCTH ceramics simultaneously, which present significant dependency on the Eu doping content. Under 457-nm light excitation, the Eu-BCTH ceramics emit strong red fluorescence centering around 689 nm, relating to the 5D0 → 7F4 electron transition, accompanied by several weak fluorescence emissions. The 0.5 mol% Eu-doped BCTH ceramics present excellent piezoelectric and florescent properties simultaneously.

Ferroelectric Mn-doped 0.935Bi0.5Na0.5TiO3-0.065BaTiO3 (MnBNBT) thin films were fabricated on (111)Pt/Ti/SiO2/Si substrates via pulsed laser deposition under different oxygen pressures. (100)-preferred orientation and dense films with perovskite structure were grown. The MnBNBT thin film deposited at an optimized oxygen pressure of 25 Pa exhibited a well-defined ferroelectric P-E loop with an average remnant polarization Pr of 27 μC/cm2, a coercive field Ec of 5.7 kV/mm, and a high relative dielectric constant of 1295. The leakage current characteristics were assessed, demonstrating that the ohmic conduction behaviors and Fowler-Nordheim tunneling were the main mechanisms of the MnBNBT thin films. Piezoelectric force microscopy indicated that the MnBNBT films possessed favorable local piezoelectric responses and multidomain states. The results suggest that the lead-free thin film produced is potentially applicable in ferroelectric and piezoelectric devices.

The phase transition process of pure and 0.5 at% Fe-doped 0.95(Na1/2Bi1/2)TiO3–0.05BaTiO3 (NBBT5) single crystals under in-situ electric-field was investigated using the Raman spectroscopy. The pure NBBT5 exhibited R3c (a−a−a− octahedral tilting) symmetry when subjected to an external electric field (E) up to 70 kV/cm. While after the Fe-doping, the crystal underwent a transition from P4bm (a0a0c+ octahedral tilting) to P4mm (a0a0c0 octahedral tilting) phase under E of 30–40 kV/cm. The results indicated that the octahedral tilting in the Fe-NBBT5 was substantially suppressed by the electric field, which was suggested to contribute to the enhanced piezoelectric response compared to the pure one.

In this work, we systematically studied the deposition, characterization, and crystal structure modeling of ScAlN thin film. Measurements of the piezoelectric device’s relevant material properties, such as crystal structure, crystallographic orientation, and piezoelectric response, were performed to characterize the Sc0.29Al0.71N thin film grown using pulsed DC magnetron sputtering. Crystal structure modeling of the ScAlN thin film is proposed and validated, and the structure–property relations are discussed. The investigation results indicated that the sputtered thin film using seed layer technique had a good crystalline quality and a clear grain boundary. In addition, the effective piezoelectric coefficient d33 was up to 12.6 pC/N, and there was no wurtzite-to-rocksalt phase transition under high pressure. These good features demonstrated that the sputtered ScAlN is promising for application in high-coupling piezoelectric devices with high-pressure stability.

This paper investigates the excitation and propagation characteristics of a piezoelectric acoustic wave propagating in a rotated Y-cut X-propagating Pb(In0.5Nb0.5)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) relaxor-based ferroelectric single crystal substrate. Numerical simulations were performed to evaluate the acoustic wave properties by FEM software COMSOL. For comparison, two types of structures are taken into consideration: one is the traditional metal electrode/YX-PIN-PMN-PT and the other is silicon dioxide (SiO2) overlay/metal electrode/YX-PIN-PMN-PT substrate. It is shown that shear-horizontal (SH)-type piezoelectric boundary acoustic waves (PBAW) exist in the SiO2 overlay/metal electrode/YX-PIN-PMN-PT substrate and offer a fairly large electromechanical coupling factor K2 of 30%. Compared to a surface acoustic wave excited in the metal electrode/YX-PIN-PMN-PT substrate, enlarged phase velocity and significantly improved quality factor (∼3500) are simultaneously obtained for SH-type PBAW, which are promising for electromechanical transducer applications with high performance.

Perovskite oxides with luminescent ions hold great promise in optoelectronic devices because of their outstanding thermal stabilities and electro-optic performance. As one typical perovskite upconversion (UC) host material, lead-free potassium sodium niobate ((K, Na)NbO3/(KxNa1-x)NbO3 or KNN) has attracted much attention in recent years. In the present work, a novel routine was developed to tune the upconversion photoluminescence (UC PL) performance by controlling the oxygen vacancy concentration in the KNN matrix, based on the 0.1% Er3+-doped KNN (Er-KNN) single crystals grown for the first time. UC PL properties, conductivity and defect chemistry of the single crystals were systematically investigated. The UC PL intensity of the as-grown Er-KNN material could be enhanced by 20 times after oxygen atmosphere annealing at 800 °C and fully quenched after vacuum annealing. What's more, by annealing under an oxygen atmosphere and vacuum, the conductivity of the Er-KNN sample was successfully tuned for more than 8 orders of magnitude. The super-wide range tunability of UC PL performance and conductivity could be explained by oxygen vacancies which gave rise to Nb5+-Nb4+ valence alternation. Because of the modulated photoluminescence properties and conductivity, our grown Er-KNN single crystals have great potential for use in multifunctional devices.

The pyroelectric and piezoelectric properties of 4 at% Mn-doped Bi4Ti2.9W0.1O12 (BiTW-Mn) Aurivillius ceramic were investigated and compared to Bi4Ti2.9W0.1O12 (BiTW) counterpart, which were fabricated using a conventional solid state reaction method. High resistivities of 4.9 × 1012 and 2.5 × 1011 Ω cm at 100 °C were obtained in the W-doped and W/Mn-codoped BiT ceramics, respectively. They showed similar activation energies and ionic-p-type mixed conduction mechanisms. Higher pyroelectric coefficients of 57.1 μC/m2K and piezoelectric coefficients of 21 pC/N, as well as much lower dielectric loss of 0.003 were achieved in W/Mn-codoped ceramics. These property changes were mainly induced by M n Ti − V o defect dipoles. The effect of acceptor doping was evidenced by an internal bias field, shown by a horizontal offset in the polarization-field behavior. The improved properties together with high thermal stability indicate that BiTW-Mn may be a promising candidate for pyroelectric and piezoelectric devices at elevated temperatures.

In this work, the (0.94-x)(Na0.5Bi0.5)TiO3-0.06Ba(Zr0.05Ti0.95)O3-x(Sr0.8Bi0.1□0.1)TiO2.95 (NBT-BZT-xSBT) ternary relaxor ferroelectrics were chosen as the studied compositions, and the in-situ electric-field-dependent Raman spectra and PFM measurements were performed to systematically investigate the structural distortion and local polarization switching. Results showed that the SBT enhances the relaxor degree and depresses the field-induced local distortion. The higher field required initially for obtaining polarization saturation with increasing SBT concentration is related to overcoming the hindrance posed by the local structural heterogeneity. Most intriguingly, a giant and temperature-insensitive electrostrictive effect (Q33 = 0.035 m4/C2, RT∼120 °C: variation less than 2%) was achieved in SBT5 composition. Such performance is one of the best values ever reported on lead-free and lead-based electrostrictive materials. A modified Landau model was proposed to phenomenologically elaborate the underlying mechanisms. Our findings illustrate that understanding structural changes at multiple length scale will be helpful for designing novel lead-free piezoceramics with high performance.

The dielectric, ferroelectric and piezoelectric properties of the high-Curie temperature (high-T C ) 0.15Pb(Mg 1/3 Nb 2/3 )O 3 -0.38PbHfO 3 -0.47PbTiO 3 (0.15PMN-0.38PH-0.47PT) ceramics synthesized by three different methods were investigated. The 0.15PMN-0.38PH-0.47PT ceramics prepared by the partial oxalate route present the best electrical properties (T C = 291 °C, e m = 28,937, P r = 32.89 μC/cm 2 , E c = 9.35 kV/cm, d 33 = 456.2 pC/N and K p = 67.2%) and excellent thermal stability of the piezoactivity properties under T C . Piezoresponse force microscopy (PFM) and confocal Raman microscopy (CRM) were employed to probe the nanoscale mechanism responsible for the performance difference of the 0.15PMN-0.38PH-0.47PT ceramics prepared by three different methods, disclosing the existence of the fine stripe domains, which make up the big island domains. The interplay between the macroscopic properties and nanoscopic domain structures of the 0.15PMN-0.38PH-0.47PT ceramics has been revealed. The better ferroelectric and piezoelectric response arise from the smaller domain size, which reduces the domain wall energy; whereas the higher coercive field E c detected by the polarization-electric field (P-E) loops results from the harder domain switching for the 0.15PMN-0.38PH-0.47PT ceramics prepared by the wet chemical synthesis techniques.

The 0.95(Li0.03Na0.5K0.47)(Nb0.92Sb0.05Ta0.03)O3-0.05(Ba0.5Ca0.5)ZrO3 (LNKNST-BCZ) lead-free piezoelectric ceramics were prepared by the conventional ceramic processing via the two-step sintering m...