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(K,Na)NbO3-based ceramics are deemed among the most promising lead-free piezoelectric materials, though their overall piezoelectric performance still lags behind the mainstream lead-containing counterparts. Here, we achieve an ultrahigh piezoelectric charge coefficient d33 ∼ 807 pC·N−1, along with a high longitudinal electromechanical coupling factor (k33 ∼ 88%) and Curie temperature (Tc ∼ 245 °C) in the (K,Na)(Nb1-xSbx)O3-Bi0.5Na0.5ZrO3-BiFeO3 (KNN-xSb) system through structural flexibility and grain orientation strategies. Phenomenological models, phase field simulations and high-angle annular dark-field scanning transmission electron microscopy reveal that the structural flexibility originates from the high Coulomb force between K+/Na+ ions and Sb ions in the KNN-xSb system, while the grain orientation promotes the displacement of B-site cations leveraging the engineered domain configuration. As a result of its excellent comprehensive piezoelectric properties, the textured KNN-5Sb/epoxy 1-3 piezoelectric composite is found to possess a broader bandwidth BW = 60% and higher amplitude output voltage than commercial PZT-5 and other KNN counterparts. These findings suggest that the textured KNN-5Sb ceramics could potentially replace current lead-based piezoceramics in transducer applications. The authors achieve piezoelectric coefficient d33 ∼ 807 pC·N−1, along with high k33 ∼ 88 % and Tc ∼ 245 °C in (K,Na)(Nb1-xSbx)O3-Bi0.5Na0.5ZrO3-BiFeO3 system through structural flexibility and grain orientation strategies. [ABSTRACT FROM AUTHOR]

This paper reports enhanced high-temperature piezoelectric properties of Bi(Zn0.5Ti0.5)O3-modified BiFeO3-BaTiO3 (BF–BT-xBZT) ceramics prepared by two-step sintering method. The resultant ceramics show a symmetrical transition from a rhombohedral–pseudo-cubic (R-PC) phase coexistence to main PC phase with the increase of x, whose R-PC fraction (CR/CPC) is 53.3/46.7, 52.9/47.1, 50.2/49.8, 27.4/72.6, 15.3/84.7 when x = 0, 0.005, 0.01, 0.03, 0.05, respectively. The modification of BZT inhibits the grain growth, reduces the leakage current and gradually drives ferroelectric to relaxor transition. Optimal piezoelectric properties: d33 = 193 pC N−1, Pr = 20.6 μC cm−2, TC = 503 °C and kp = 36% achieved at x = 0.01 composition, which is due to the synergistic effect of an appropriate CR/CPC ratio, improved insulation and good polarization performance. In addition, the depolarization temperature Td is close 280–312 °C, and the high-temperature d33 further increases to 286–347 pC N−1, which shows a good application prospect of lead-free piezoceramics at high temperature. Our work also confirms that the addition of (Zn0.5Ti0.5)3+ and two-step sintering method are an effective and convenient strategy to improve the high-temperature electrical performance of BiFeO3–BaTiO3 based lead-free ceramics. [ABSTRACT FROM AUTHOR]

The enhanced piezoelectric and ferroelectric properties of the tetragonal 0.67BiFeO3–0.33BaTiO3 (BF–33BT) ceramics without MnO2 doping or other dopants via tailoring sintering temperature (TS) and dwell time (td) are reported. All ceramics crystallized in a single tetragonal phase, independent of the adopted TS and td. As the TS or td is increased, the BF–33BT ceramics show an increase in grain size and in relative density, while TS > 980 °C or td > 6 h would result in more oxygen vacancies caused by Bi3+ evaporation and/or reduction of Fe3+ to Fe2+, along with a reduced relative density and an increased current leakage density. Because of the increased grain size, the higher relative density, and relatively less oxygen vacancies, high d33 = 151 pC/N and Pr = 25.9 μC/cm2 were achieved in tetragonal BF–33BT ceramics with TS = 980 °C and td = 6 h. In addition, large unipolar strain of 0.146% and d 33 ∗ =326 pm/V (40 kV/cm), as well as high TC = 427 °C were also obtained in the BF–33BT ceramics with TS = 980 °C and td = 6 h. Our studies indicate that the grain size, the relative density, and the oxygen vacancies play important roles for the piezoelectric properties of BF–33BT ceramics. [ABSTRACT FROM AUTHOR]

BiFeO3‐BaTiO3 ceramics are promising lead‐free piezoelectric ceramics due to their high piezoelectric properties and high Curie temperature, but their high leakage current density makes the poling difficult. In this study, a decreased leakage current density by three orders of magnitude was obtained in Bi0.5Na0.5TiO3 (BNT) added 0.67BiFeO3‐0.33BaTiO3 (BF‐BT) ceramics. It was found that the largely improved insulating properties benefit from the reduced oxygen vacancies and weak reduction of Fe3+ to Fe2+ as confirmed by photoluminescence and X‐ray photoelectron spectroscopy measurements, thereby contributing to high‐temperature and high‐field poling. In addition, the introduction of BNT leaded to increased grain size. Due to the grown grains as well as reduced oxygen vacancies and Fe2+, enhanced insulating and optimal piezoelectric properties with Pr = 24.2 µC/cm2, d33 = 183 pC/N, kp = 0.28, and TC = 467°C were achieved in BF‐BT‐0.05BNT ceramics. [ABSTRACT FROM AUTHOR]

A series of solid solution of (1− x)BiFeO- xBaTiO (abbreviated as BFO- xBT at 0.24 ≤ x ≤ 0.34) were prepared to reveal the relation between phase structure and multiferroic properties. A morphotropic phase boundary (MPB) separating R phase and T one was detected in BFO- xBT system at 0.26 ≤ x ≤ 0.34. Due to R and T two -phase coexistence, high piezoelectric properties of d = 191 pC/N and k = 34.68%, as well as excellent ferroelectric properties of 2 P = 56.13 μm/cm and 2 E = 75.35 kV/cm were achieved in the BFO- xBT ceramics at x = 0.30. Moreover, a low leakage current density ( J) of 1.01 × 10-3.18 × 10 A/cm at an applied electric field of 30 kV/cm and a weak ferromagnetism with remanent magnetization M of 0.014-0.054 emu/g and coercive fields H of 946-2340 Oe were detected in BFO- xBT ceramics at 0.24 ≤ x ≤ 0.34, suggesting that the BFO-BT ceramics have promising prospects in magnetoelectric functional components. [ABSTRACT FROM AUTHOR]

BaCa xTiO3-0.04LiF (0.010 ≤ x ≤ 0.045) ceramics were prepared by normal sintering at 1100 °C in air. A two-phase coexisted region across orthorhombic and rhombohedral symmetry was designed by refining the components. The detailed phase structure was analyzed quantitatively by the Rietveld refinement. BaCa0.035TiO3-0.04LiF ceramic showed better properties with d33 = 354 pC N−1, kp = 39%, Qm = 314, and TC = 65 °C, in which the relative proportion of rhombohedral symmetry was 74.86%, the grain size was 6.0 µm and the relative density was 91%, indicating that the synergistic effect of the phase structure, fine grain, and relatively high density contributed to the outstanding piezoelectric properties. [ABSTRACT FROM AUTHOR]

( Ba1− x Ca x)( Ti0.92 Sn0.08) O3 ( x = 0.00-0.06 mol) ceramics with a high relative density over 96% were prepared by a conventional sintering method at 1480°C. At room temperature, a polymorphic phase transition from orthorhombic phase to tetragonal phase was confirmed by the XRD patterns in the composition range of 0.04 ≤ x ≤ 0.06. A high piezoelectric coefficient d33 up to 568 pC/N was obtained at x = 0.05 mol, which is higher than the other component of ( Ba, Ca)( Ti, Sn) O3 system. At the same time, the corresponding planar electromechanical coupling factor kp, converse piezoelectric coefficient dS/ dE, and dielectric constant εr reach 47.7%, 1013 pm/V, and 23000, respectively. These results indicate that the ( Ba, Ca)( Ti, Sn) O3 ceramics are a promising candidate to replace for the lead-based piezoelectric materials. [ABSTRACT FROM AUTHOR]

Abstract: BaTiO3–xLiF ceramics were prepared by a conventional sintering method using BaTiO3 powder about 100nm in diameter. The effects of LiF content (x) and sintering temperature on density, crystalline structure and electrical properties were investigated. A phase transition from tetragonal to orthorhombic symmetry appeared as sintering temperatures were raised from 1100°C to 1200°C or as LiF was added from 0mol% to 3mol%. BaTiO3–6mol% LiF ceramic sintered at 1000°C exhibited a high relative density of 95.5%, which was comparable to that for pure BaTiO3 sintered at 1250°C. BaTiO3–4mol% LiF ceramic sintered at 1100°C exhibited excellent properties with a piezoelectric constant d 33 =270pC/N and a planar electromechanical coupling coefficient k p =45%, because it is close to the phase transition point in addition to high density. [Copyright &y& Elsevier]

Polycrystalline InO ceramics co-doped with Zn and Nd were prepared by the spark plasma sintering (SPS) process, and microstructure and thermoelectric (TE) transport properties of the ceramics were investigated. Our results indicate that co-doping with Zn and Nd shows a remarkable effect on the transport properties of InO-based ceramics. Large electrical conductivity (~130 S cm) and thermopower (~220 μV K) can be observed in these InO-based ceramic samples. The maximum power factor (PF) reaches 5.3 × 10 W m K at 973 K in the InNdZnO sample, with a highest ZT of ~0.25. [ABSTRACT FROM AUTHOR]

Abstract: Single-phase polycrystalline La0.08Sr0.92TiO3 ceramics were prepared by spark plasma sintering (SPS) using sol–gel-derived powders. The La0.08Sr0.92TiO3 bulks had highly relative density (∼92%), and the grain size of the samples obviously grew from 300 nm to 3 μm when the SPS temperature increased from 1203 to 1473 K. The electrical conductivity increased with SPS-processing temperature owing to the increase of relative density, grain size, and oxygen vacancies due to the reducing atmosphere of SPS. The absolute value of Seebeck coefficient increased as the SPS temperature increased from 1203 to 1373 K, and then decreased by further increasing SPS temperature to 1473 K. The sample SPSed at 1373 K had the largest absolute value of Seebeck coefficient of 196 μVK−1 at 679 K. Sol–gel process and SPS can significantly decrease the thermal conductivity of SrTiO3 based ceramics, whose lowest value was reduced to 1.19 Wm−1k−1 at 773 K in the sample SPSed at 1203 K. The maximum ZT value of 0.08 was obtained at 679 K for the sample SPSed at 1473 K. [Copyright &y& Elsevier]

Here, the phase structure, microstructure, and electrical and luminescent properties of 0.93(Na 0.5 Bi 0.5) 1- x TiO 3 -0.07BaTiO 3 - x Eu3+ (BNBT- x Eu, 0.000≤ x ≤ 0.020) ceramics were investigated. Coexisting rhombohedral (R) and tetragonal (T) phases were obtained in all ceramics. As the Eu3+ content increased, the phase structure changed from a mixture of R - T phases to a main T phase with a minor R phase, along with a decreased grain size. The T m of the BNBT- x Eu ceramics increased from 283 °C to 302 °C upon increasing the Eu3+ content, and the permittivity curve became broader, especially at a high doping content. The ferroelectric and piezoelectric properties were enhanced due to appropriate ratio of R and T phases, increased density, reduced T d , reduced E C , and reduced current density caused by Eu3+ doping. The maximum remnant polarization of P r = 35.5 μC/cm2 and piezoelectric constant of d 33 = 214 pC/N were achieved for the x = 0.010 ceramic. Eu3+ doped BNBT ceramics exhibited red fluorescence at 614 nm derived from the 5D 0 →7F 2 transition of Eu3+ under 466 nm excitation. These results demonstrate the potential applications of the Eu3+ doped BNBT ceramics for novel integrated electronic devices. [ABSTRACT FROM AUTHOR]

A correction of the article "High Piezoelectric d33 Coefficient in Li/Ta/Sb-Codoped Lead-Free (Na,K)NbO3 Ceramics Sintered at Optimal Temperature" published in a prior issue is presented.

A correction of the article "Effect of Ta Content on Phase Structure and Electrical Properties of Piezoelectric Lead-Free [(Na0.535K0.480)0.942Li0.058](Nb1− xTa x)O3 Ceramics" published in a prior issue is presented.

Abstract: We report the enhancement of piezoelectric properties of (Ba0.95Ca0.05)(Ti1−x Zr x )O3 (BCTZx) ceramics by optimizing Zr content in the range of 0≤ x ≤15at.%. The BCTZx were synthesized by the solid-state reaction method and sintered at 1350°C in a reducing atmosphere of pO2 =5×102 Pa, for potential co-firing with base metal electrodes (BMEs). The BCTZx ceramics were characterized by an orthorhombic to pseudocubic polymorphic phase transition (PPT) at 5≤ x ≤7at.%, based on X-ray diffraction patterns. The orthorhombic to pseudocubic phase-transition temperature T 1 was shifted to 36°C near room temperature for Zr content of x =4at.%. The piezoelectric constant d 33, electromechanical coupling coefficient k p, and dielectric constant ɛ r were optimized to 338 pC/N, 36%, and 2070, respectively. The results indicate that optimizing Zr content is an effective way to enhance the piezoelectric properties of (Ba,Ca)(Ti,Zr)O3 ceramics, which are promising as a lead-free piezoelectric candidate. [ABSTRACT FROM AUTHOR]

Abstract: Co-firing of piezoceramics with metals is drawing ever-increasing attention. This article reports Ni-particle-dispersed [Li0.06(K0.5Na0.5)0.94]NbO3 (LKNN/Ni) lead-free piezoelectric composites that were sintered in a protective atmosphere of nitrogen gas. The base metal Ni was not oxidized and the piezoelectric LKNN preserved the perovskite structure. The microstructure observations show that Ni particles were uniformly dispersed in LKNN ceramics matrix. With increasing Ni content from 0 to 20vol%, the piezoelectric constant d 33 of the LKNN/Ni composites decreased from 165 to 23pC/N, and the corresponding dielectric constant ɛ r greatly increased. The 95%LKNN-5%Ni composite still exhibited a typical ferroelectric loop; however, the P-E curves measured for Ni>5vol% composites demonstrated some metallic characteristics. The LKNN/Ni composites could find applications in piezoelectric actuators with functionally graded microstructure (FGM). [Copyright &y& Elsevier]

Abstract: (Ba0.95Ca0.05)(Ti0.88Zr0.12)O3 (BCTZ) ceramics have been produced in a protective atmosphere of industrial N2 gas for potential piezoelectric applications. For comparison, the ceramics were also sintered at 1200–1400°C in air. The results revealed that the reducing atmosphere of pO2 =5×102 Pa had no substantial effect on the phase structure or the microstructure of the BCTZ ceramics. The XRD patterns suggested a tetragonal to pseudocubic phase transition at sintering temperatures above 1300°C in both atmospheres. The nitrogen-sintered BCTZ samples had higher dielectric constants ɛ r but lower electromechanical coupling coefficients k p than the air-sintered samples. The piezoelectric constant d 33 for the BCTZ ceramics was not significantly influenced by the reducing atmosphere of pO2 =5×102 Pa. The correlation of dielectric and piezoelectric properties of the BCTZ ceramics with the sintering temperature was explained based on a competing mechanism between phase structure and microstructure. [Copyright &y& Elsevier]

Abstract: Porous piezoceramics have promising applications in underwater sonar detectors or medical ultrasonic imaging. We report the electrical and acoustic properties based on different pore microstructures of porous lead zirconate titanate (PZT) ceramics, fabricated using stearic acid (SA) and polymethylmethacrylate (PMMA) as pore-forming agents. The corresponding ferroelectric and piezoelectric properties decreased with increasing porosity due to the decrease in volume fraction of PZT phase, and were in good agreement with a modified cubes model in the case of isolated porosity. The corresponding acoustic impedance decreased from 16 to 8MRayls (106 kg/m2 s), with increasing porosity from 3% to 43%, due to low acoustic impedance of pore phase. The electrical properties of porous PZT ceramics were closely associated with porosity and the interconnection of pores, but only slightly associated with the shape of pores. However, the acoustic impedance was only connected to porosity, not to either shape or interconnection of pores. [Copyright &y& Elsevier]

Ferroelectric perovskite oxides exhibit the bulk photovoltaic effect, which enables an above-bandgap photovoltage, controllable photocurrent response, and higher efficiencies. Herein, the phase structure, ferroelectric, dielectric, light absorption, and photovoltaic properties in (Ba 0.95 Ca 0.05)(Ti 0.92 Sn 0.08- x Zr x)O 3 (BCTSZ x) ceramics were investigated. All BCTSZ x samples had good ferroelectric properties along with a narrow band gap (E g = 2.53–2.60 eV). A large photovoltaic response under AM 1.5 G simulated sunlight was observed in the poled BCTSZ 0.06 ceramics, in which the maximum short-circuit current (J SC = 3.66 nA cm−2) as well as the highest transient current (J TC = 32.56 nA cm−2) and photocurrent (J PC = 12.63 nA cm−2) were obtained in 500 μm-thick sample negatively poled at 30 kV cm−1. Our results deepen an understanding of the ferroelectric photovoltaic mechanism of perovskite materials and provide a new material for photovoltaic and multifunctional applications. [ABSTRACT FROM AUTHOR]

Recently, BiFeO 3 –BaTiO 3 (BF-BT) lead-free ferroelectric ceramics have been widely concerned and deemed as one of the most promising candidates for lead-free energy-storage material because of their high spontaneous polarization and excellent energy storage properties. Herein, a series of Bi 1- z La z FeO 3 - x BaTiO 3 + y MnO 2 (BL z F- x BT- y Mn at 0.45 ≤ x ≤ 0.60 mol, 0.0 ≤ y ≤ 0.4% mol and z = 0 or 0.02 mol) ceramics were prepared to reveal their energy-storage performance. With increasing x , the breakdown strength (BDS) increases, while the maximum polarization (P max), remanent polarization (P r), and the difference value between P max and P r (Δ P) decrease. Because of the high BDS and Δ P , a large energy storage density W re = 1.08 J/cm3 is achieved in BF-0.48BT ceramics as the electric field is 130 kV/cm. In addition, with increasing y and z , the increasing BDS and Δ P have been observed. Due to the improvement in BDS and Δ P , an excellent W re = 1.22 J/cm3 was achieved in Bi 1- z La z FeO 3 - x BaTiO 3 + y MnO 2 ceramics at x = 0.48, y = 0.3% and z = 0.02. This work provides the clue for application of the high-power-energy BF-BT ceramics. [ABSTRACT FROM AUTHOR]