Electromechanical Coupling Coefficient Kp Research Articles

LiNbO3-induced phase structure evolution and improved piezoelectric properties in BiFeO3–BaTiO3 ceramics

Eco-friendly (0.73-x)Bi1.05FeO3-xLiNbO3-0.27BaTiO3 ternary ceramics were designed and prepared via a solid-state sintering route. Based on the X-ray diffraction results and Rietveld refinement, it was found that the structure of the ceramics transformed from rhombohedral to tetragonal symmetry with the addition of LiNbO3, and at x = 0.003, there existed a morphotropic phase boundary separating the two phases. Near the phase boundary, the largest values were achieved for the piezoelectric constant d33 and planar electromechanical coupling coefficient kp, being 180 pC/N and 0.27, respectively. Due to the addition of LiNbO3, the grain size tended to become smaller. Additionally, the ceramics were transitioned from normal to relaxor ferroelectrics with increasing x. Despite the fact that the LiNbO3 addition would result in a gradual decrease of Curie temperature, a relatively high Curie temperature (535 °C) was still maintained at x = 0.003, the phase boundary composition, which also showed good temperature stability of piezoelectric properties. These experimental results can provide a reference for the practical applications of high-temperature lead-free ceramics.

Enhanced soft piezoelectric properties of Sb2O3 doped 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 materials

In this paper, we have studied the soft piezoelectric properties of 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 doped with Sb2O3. The optimal piezoelectric charge constant and dielectric permittivity of the calcined and sintered 0.5Ba(Zr0.2Ti0.8)O3–0.5(Ba0.7Ca0.3)TiO3 were determined by varying the Sb2O3 content. The mol% of Sb2O3 was set to 0, 0.05, 0.1, 0.15, and 0.2, and the doped ceramics were sintered at a temperature of 1475 °C. The piezoelectric charge constant d33, electromechanical coupling coefficient kp, and dielectric permittivity εr of the doped ceramics increased with the increasing Sb2O3 content, whereas their Curie temperature Tc slightly decreased. At 0.1 mol% of Sb2O3, the highest piezoelectric charge constant, electromechanical coupling coefficient, and dielectric permittivity values were obtained. Although the Curie temperature was slightly lowered, the dielectric permittivity improved. 0.5BZT-0.5BCT doped with Sb2O3 exhibited a high remnant polarization Pr even when a weak coercive electric field Ec was applied, resulting in an easy polarization. It can be seen that the improved electrical properties and the behavior of the P-E hysteresis loop through the dopant addition of Sb2O3 are close to the soft piezoelectric characteristics. Thus, the synthesized lead-free and Sb2O3-doped ceramics, with excellent piezoelectric properties and depolarization behaviors, are expected to replace lead-based ceramics and will be useful in energy converters, such as piezoelectric transformers.

Effects of heterovalent ions doping-induced oxygen octahedral distortion and defect chemical change on piezoelectric characteristics and thermal stability of PHT-PIN ceramics

Electromechanical devices require functional materials possessing excellent piezoelectric properties, good thermal stability, and high electromechanical coupling coefficients. To modulate the piezoelectric, dielectric, and electromechanical characteristics of 0.89Pb(Hf0.47Ti0.53)O3-0.11Pb(In1/2Nb1/2)O3 (PHT-PIN) piezoelectric ceramics, heterovalent ions of lithium (Li) and tungsten (W) were doped through a traditional solid-phase reaction approach. On the one hand, large lattice distortions caused by the doped W6+ resulted in the shortening of BO bonds while an increase in the local displacement of B-site ions. Moreover, a mismatch occurred for the oxygen octahedral dimensions, and a subsequent disruption of the long-ranged ordered ferroelectric domains was observed, which resulted in the formation of microdomains. On the other hand, the changes in the concentration of oxygen vacancy defects induced by the Li and W doping inside the ceramic were comprehensively analyzed. The decrease in the concentration of oxygen vacancies was found to be accompanied by the enhancement of piezoelectric properties of the material. Excellent comprehensive performance (piezoelectric coefficient d33 = 655 pC N−1, Curie temperature Tc = 321.1 °C, dielectric constantεr = 3352.31, electromechanical coupling coefficient kp = 0.67, and residual polarization strength Pr = 55 μC cm−2) was obtained for 0.2 mol % doping amount of Li+ and W6+ ions. This work, therefore, proposes a novel strategy for the origin of piezoelectric properties and inspires doping of other heterovalent ions to improve the piezoelectric properties of ceramics. It further promotes the development of Pb-based piezoelectric ceramics for electromechanical devices that can efficiently operate under high-temperature environments.

Enhanced insulation and ferro/piezo-electric properties of BiFeO3–BaTiO3via synchronous B-site co-doping and quenching treatment

Lead-free piezoelectric ceramics 0.7BiFe1-x(Zn0.5Sn0.5)xO3-0.3BaTiO3 [BF(ZS)x-BT] were successfully prepared using the solid-state reaction method. The dual effects of B-site Zn/Sn co-doping and quenching on the structure and piezoelectricity of BF(ZS)x-BT were investigated. All samples showed a distinct perovskite structure, characterized by the simultaneous presence of rhombohedral (R) and pseudo-cubic (pC) phases. The insulation and electrical properties were significantly increased by appropriate Zn/Sn co-doping and quenching treatment. The long parallel strip domains and enhanced lattice distortion synergistically contribute to the outstanding piezoelectricity (d33 = 203 pC/N) and a high Curie temperature (Tc = 493 °C) in quenched BF(ZS)0.003-BT. Furthermore, the quenching treatment was found to further improve the piezoelectric property and enhance its high-temperature stability, as demonstrated by the in-situ electromechanical coupling coefficient (kp) and thermal depolarization test. The d33 of the quenched BF(ZS)0.003-BT was maintained at 186 pC/N around 400 °C, highlighting its promising applications in medium-high temperature conditions.

Characteristics of NaNbO3 templates and improvement of electrical properties of textured KNLNS-BNKT ceramics

In this study, plate-like perovskite NaNbO3 (NN) templates were formed from Bi2.5Na3.5Nb5O18 (BiNN5) precursors via a molten salt method. The structure and microstructure of BiNN5 precursors and NN templates were studied. As a result, the platelike BiNN5 precursor particles have a bismuth layer perovskite structure, which is the basis for forming the synthesized plate-like NN particles that have a high aspect ratio with a width of 2-7 μm, a length of 5-12 μm and a thickness of 0.5-1 μm. From NN templates, we fabricated textured lead-free 0.98(K0.48Na0.48Li0.04)(Nb0.95Sb0.05)O3 − 0.02Bi0.5(Na0.4K0.1)TiO3 (KNLNS- BNKT) ceramic by the grain orientation technique. Experimental results show that the KNLNS-BNKT ceramics have a single-phase orthorhombic structure in which textured KNLNS-BNKT ceramics with 67% grain orientation. The electrical properties of the oriented ceramic are significantly improved compared to the non-oriented ceramic fabricated by the traditional method. Specifically, the electrical properties of the resulting KNLNS-BNKT oriented ceramics have a high dielectric constant (ε = 1323, an increase of 17%); large remnant polarization (Pr = 13.5 mC/cm2, an increase of 11.9%); high piezoelectric coefficient (d33 = 205 pC/N, an increase of 32%) and high electromechanical coupling coefficient (kp = 0.4, an increase of 11%).

Lead zirconate titanate-based ceramics with high piezoelectricity and broad usage temperature range

Piezoceramics have long faced the challenge of achieving both a high Curie temperature (TC) and outstanding electrical properties due to thermal depolarization. To address this, we introduced a novel two-step synergistic strategy in synthesizing lead zirconate titanate (PZT)-based x[(1–y)BiYO3-yFe2O3)]-(1–x)Pb(Zr0.53Ti0.47)O3 [abbreviated as xBYF(y)-PZT] ceramics, where co-doping of Fe2O3 and BiYO3 significantly influences dielectric and piezoelectric properties. Our breakthrough composition, 0.01BYF(0.6)-PZT, showcases a unique coexistence of rhombohedral and tetragonal phases. It boasts impressive figures, including a piezoelectric coefficient d33 of 467 pC N−1, a TC of 381 °C, an electromechanical coupling coefficient (kp) of 68%, and a coercive field (Ec) of 12 kV cm−1, displaying both “softening” and “hardening” characteristics. In-depth analysis with in-situ X-ray diffraction and transmission electron microscopy unveils the critical role of multiphase coexistence and local heterostructures in enhancing piezoelectric responses through synergistic effects. Notably, this innovative composition with x = 0.01 showcases exceptional thermal stability across a broad operating temperature range (30–350 °C) and delivers an in-situ d33 value of 790 pC N−1. These compelling findings underscore the potential of BYF-modified PZT ceramics as promising candidates for high-temperature piezoelectric applications.

High-stability quinary lead-based piezoelectric ceramics with high piezoelectric properties

Piezoceramics with the formula Pb0.93Sr0.06Ba0.01(Mg1/3Nb2/3)0.035(Ni1/3Nb2/3)0.2 (Sb1/2Nb1/2)0.015(ZrxTi1−x)0.75O3 + 0.5 wt. % Li2CO3, where x = 0.51, 0.50, 0.49, 0.48, 0.47, and 0.46, have been made using the one-step solid-state method. The phase structure and electrical properties were systematically investigated in the quinary system. Here, the crystalline structure transformed gradually from the rhombohedral to tetragonal phase with decreasing Zr content. More importantly, the effective piezoelectric coefficient d33* of the ceramics demonstrates an excellent thermal stability below the Curie temperature. Meanwhile, piezoelectric ceramics with x = 0.49 exhibited the extraordinary electrical properties near the morphotropic phase boundary. A huge piezoelectric coefficient d33 = 853 pC/N, high Curie temperature TC = 152 °C, and the electromechanical coupling coefficients kp = 67.4%, kt = 63.5%, and k33 = 67.4% were obtained at the composition of x = 0.49, which may lead a promising future for the transducer applications.

Phase Structure and Electrical Properties of 0.28PIN-0.32PZN–(0.4-x) PT-xPZ Piezoelectric Ceramics

Piezoelectric constant and Curie temperature are two important parameters of piezoelectric materials, but currently most piezoelectric materials have the problem of obtaining both high piezoelectric coefficient and Curie temperature. In this work, quaternary piezoelectric ceramics of 0.28Pb(In1/2Nb1/2)O3-0.32Pb(Zn1/3Nb2/3)O3–(0.4-x)PbTiO3-xPbZrO3 (x = 0~0.25) were designed and prepared by a solid-phase method, and the phase structure, dielectric, piezoelectric and ferroelectric properties of 0.28PIN-0.32PZN-(0.4-x)PT-xPZ piezoelectric ceramics were investigated by regulating the Zr/Ti ratio. The results show that the selected compositions are located in the MPB region, and the ceramic samples of each component display high density, the piezoelectric constant (d33) and the electromechanical coupling coefficient (kp) increase and then decrease with the increase of x. The optimum piezoelectric properties are found in compositions at x = 0.1, which showed a high piezoelectric coefficient d33 of 450 pC/N and high Curie temperature Tc of 272 °C. It is promising for use in high-temperature piezoelectric transducers.

High-Temperature Piezoelectric Response and Thermal Stability of BiGaO3 Modified BiFeO3–BaTiO3 Lead-Free Piezoelectric Ceramics

BiGaO3 doped BiFeO3–BaTiO3 ceramics were prepared by the traditional solid-phase synthesis process. The phase analysis, microstructure, piezoelectric, ferroelectric, dielectric properties, and thermal stability of 0.7BiFeO3-(0.3 − x)BaTiO3-xBiGaO3 (Abbreviated as BF–BT-xBG) were investigated. The results show that the ceramics have rhombohedral (R) and tetragonal (T) structures. Particle dimensions gradually get bigger with the increase of BiGaO3 concentration, and dense ceramic grains were observed through SEM. Electrical properties of BF–BT-xBG are improved after adding a small amount of BiGaO3: piezoelectric constants d33 = 141 pC/N, electromechanical coupling coefficient kp = 0.314, mechanical Quality Factor Qm = 56.813, dielectric loss tanδ = 0.048, residual polarization intensity Pr = 18.3 µC/cm2, Curie temperature Tc = 485.2 °C, depolarization temperature Td = 465 °C for x = 0.003. The “temperature-piezoelectric performance” curve under in situ d33 indicates that piezoelectric properties d33 increase rapidly with increasing temperature. Remarkably, the piezoelectric response d33 reaches a maximum of 466 pC/N at a temperature T = 340 °C, and afterward, reduces gradually to zero with increasing temperature until 450 °C.

Yttrium and Niobium Elements Co-Doping and the Formation of Double Perovskite Structure Ba2YNbO6 in BCZT.

The (Ba0.85Ca0.15) (Ti0.90Zr0.10)O3 + x Y3+ + x Nb5+ (abbreviated as BCZT-x(Nb + Y), x = 0 mol%, 0.05 mol%, 0.1 mol%, 0.2 mol%, 0.3 mol%) lead-free piezoceramics samples were prepared by a traditional solid-state sintering method. And the effects of Yttrium and Niobium elements (Y3+ and Nb5+) co-doping on the defect, phase and structure, microstructure, and comprehensive electrical properties have been investigated. Research results show that the Y and Nb elements co-doping can dramatically enhance piezoelectric properties. It is worth noting that XPS defect chemistry analysis, XRD phase analysis and TEM results together show that a new phase of double perovskite structure Barium Yttrium Niobium Oxide (Ba2YNbO6) is formed in the ceramic, and the XRD Rietveld refinement and TEM results show the coexistence of the R-O-T phase. Both these two reasons together lead to significant performance improvements of piezoelectric constant (d33) and planar electro-mechanical coupling coefficient (kp). The functional relation between temperature and dielectric constant testing results present that the Curie temperature increases slightly, which shows the same law as the change of piezoelectric properties. The ceramic sample reaches an optimal performance at x = 0.1% of BCZT-x(Nb + Y), where d33 = 667 pC/N, kp = 0.58, εr = 5656, tanδ = 0.022, Pr = 12.8 μC/cm2, EC = 2.17 kV/cm, TC =92 °C, respectively. Therefore, they can be used as potential alternative materials to lead based piezoelectric ceramics.

Enhanced Piezoelectric, Ferroelectric, and Electrostrictive Properties of Lead-Free (1-x)BCZT-(x)BCST Electroceramics with Energy Harvesting Capability.

Next-generation electronics and energy technologies can now be developed as a result of the design, discovery, and development of novel, environmental friendly lead (Pb)-free ferroelectric materials with improved characteristics and performance. However, there have only been a few reports of such complex materials' design with multi-phase interfacial chemistry, which can facilitate enhanced properties and performance. In this context, herein, novel lead-free piezoelectric materials (1-x)Ba0.95 Ca0.05 Ti0.95 Zr0.05 O3 -(x)Ba0.95 Ca0.05 Ti0.95 Sn0.05 O3 , are reported, which are represented as (1-x)BCZT-(x)BCST, with demonstrated excellent properties and energy harvesting performance. The (1-x)BCZT-(x)BCST materials are synthesized by high-temperature solid-state ceramic reaction method by varying x in the full range (x = 0.00-1.00). In-depth exploration research is performed on the structural, dielectric, ferroelectric, and electro-mechanical properties of (1-x)BCZT-(x)BCST ceramics. The formation of perovskite structure for all ceramics without the presence of any impurity phases is confirmed by X-ray diffraction (XRD) analyses, which also reveals that the Ca2+ , Zr4+ , and Sn4+ are well dispersed within the BaTiO3 lattice. For all (1-x)BCZT-(x)BCST ceramics, thorough investigation of phase formation and phase-stability using XRD, Rietveld refinement, Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM), and temperature-dependent dielectric measurements provide conclusive evidence for the coexistence of orthorhombic + tetragonal (Amm2 + P4mm) phases at room temperature. The steady transition of Amm2 crystal symmetry to P4mm crystal symmetry with increasing x content is also demonstrated by Rietveld refinement data and related analyses. The phase transition temperatures, rhombohedral-orthorhombic (TR-O ), orthorhombic- tetragonal (TO-T ), and tetragonal-cubic (TC ), gradually shift toward lower temperature with increasing x content. For (1-x)BCZT-(x)BCST ceramics, significantly improved dielectric and ferroelectric properties are observed, including relatively high dielectric constant εr ≈ 1900-3300 (near room temperature), εr ≈ 8800-12900 (near Curie temperature), dielectric loss, tan δ ≈ 0.01-0.02, remanent polarization Pr ≈ 9.4-14 µC cm-2 , coercive electric field Ec ≈ 2.5-3.6kV cm-1 . Further, high electric field-induced strain S ≈ 0.12-0.175%, piezoelectric charge coefficient d33 ≈ 296-360 pC N-1 , converse piezoelectric coefficient ≈ 240-340 pm V-1 , planar electromechanical coupling coefficient kp ≈ 0.34-0.45, and electrostrictive coefficient (Q33 )avg ≈ 0.026-0.038 m4 C-2 are attained. Output performance with respect to mechanical energy demonstrates that the (0.6)BCZT-(0.4)BCST composition (x = 0.4) displays better efficiency for generating electrical energy and, thus, the synthesized lead-free piezoelectric (1-x)BCZT-(x)BCST samples are suitable for energy harvesting applications. The results and analyses point to the outcome that the (1-x)BCZT-(x)BCST ceramics as a potentially strong contender within the family of Pb-free piezoelectric materials for future electronics and energy harvesting device technologies.

Effect of Contents on the Electrical and Piezoelectric Properties of (1 - x)(Bi, Na)TiO3-x(Ba, Sr)TiO3 Lead-Free Piezoelectric Ceramics.

In this study, the composition of lead-free piezoelectric ceramics (1 - x)(Bi0.5Na0.5)TiO3-x(Ba0.5Sr0.5)TiO3 with excellent piezoelectric properties was investigated. Crystal analysis and electrical and piezoelectric properties were analyzed according to the content of the BST composition. A phase change from rhombohedral to tetragonal structure was observed in 0.12 BST, and the densest and most uniform microstructure was confirmed in this composition. The dielectric constant increased from 905 to 1692 as the composition of BST increased to 0.12 BST. Afterward, as the composition of BST increased, the permittivity tended to decrease. Additionally, at 0.12 BST, Pr was the highest at 23.34 μC/cm2. The piezoelectric charge constant (d33) and the electromechanical coupling coefficient (kp) were 152 pC/N and 0.37, respectively, and showed the highest values at 0.12 BST. Curie temperature (Tm) was analyzed 242 °C at 0.12 BST, the optimal composition. It was confirmed that the characteristics of 0.12 BST were excellent in all conditions. Therefore, it was confirmed that 0.12 BST is the optimal composition for (1 - x)BNT-xBST piezoelectric ceramics.

Enhanced piezoelectric properties for potassium sodium niobate lead-free piezoelectric ceramics prepared by microwave technology

Potassium-sodium niobate (Na, K)NbO3 (NKN) powder was synthesized at low temperature via microwave-assisted hydrothermal solovthermal method (MHSM). The resultant powder was characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). XRD results showed that pure (Na, K)NbO3 powder with a single perovskite structure was successfully synthesized when the concentration of mineralization exceeded 1 M. In order to reduce the volatilization of alkaline elements, NKN ceramics derived from 5M-powder were prepared in a microwave furnace. Microstructure, stoichiometry, and electrical properties of the obtained ceramics were investigated. The piezoelectric coefficient (d33), electromechanical coupling coefficient (kp) and remnant polarization (Pr) of the sample sintered at 1050 ℃ show optimal values of 132 pC/N, 38% and 26.3 µC/cm2, respectively. The results indicate that the microwave heating is a promising method for synthesizing and sintering NKN-based ceramics.

Evidence of direct and converse magnetoelectric coupling in eco-friendly 0.75(0.94Na0.5Bi0.5TiO3-0.06BaTiO3)–0.25(CoFe2O4) particulate composite

Magnetoelectric (ME) multiferroic composite exhibits the ME effect, and their interaction between piezoelectric and magnetic phase is measured in terms of ME coupling (α). ME coupling is an interesting and characteristic property of ME materials and can be evaluated by direct and indirect methods. In this work, the solid-state sintering technique has been adopted to synthesize the lead-free 0.75(0.94Na0.5Bi0.5TiO3-0.06BaTiO3)–0.25CoFe2O4 (NBBT-CFO) composite. The X-ray diffraction patterns and uniform distribution of closely packed grains reveal the coexistence of constituent phases in the composite. This composite reveals room-temperature multiferroic properties. The room temperature dielectric constant (ε′) of the poled sample displays the resonance and anti-resonance peaks at a particular frequency ∼ 455 kHz and 450 kHz, respectively. The estimated value of the electromechanical coupling coefficient (kP) is 16.69%. The direct ME and converse ME coupling study has been done through the Polarization (P) vs Electric field (E) and Magnetization (M) vs Magnetic field (H) hysteresis loop measurements of magnetically and electrically poled and unpoled samples, respectively. The variation in the polarization and magnetization value reveals the presence of direct and converse ME coupling in the composite.

Effects of (Bi0.5Li0.5)TiO3 addition on microstructures, electrical properties and thermal stability of BiFeO3-BaTiO3 piezoelectric ceramics

Herein, lead-free 0.7BiFeO3-(0.297-x)BaTiO3-x(Bi0.5Li0.5)TiO3+0.003BiGaO3+0.01MnO2 (abbreviated as BF-BT-xBLT, 0 ≤ x ≤ 0.0096) ceramics have been prepared by conventional solid-state sintering. The phase structures, microstructures, piezoelectric, ferroelectric, dielectric, and thermal stability of these materials were investigated. The XRD analysis show that rhombohedral and tetragonal phases coexist in the phase structure of BF-BT-xBLT ceramic. As the BLT concentration rises, the grain size first increases to 8.6 μm and then decreases to 6.14 μm. The grain size decreased from 7.68 μm to 5.02 μm with the decrease of sintering temperature. The piezoelectric, ferroelectric and dielectric properties of the ceramic increase first and then decrease as BLT concentration increases. The optimal electrical properties are obtained by adding 0.0012 BLT, piezoelectric constant d33 = 152 pC/N, electromechanical coupling coefficient kp = 0.321, mechanical quality factor Qm = 58.184, remnant polarization Pr = 25.07 μC/cm2, Curie temperature Tc = 485 °C and depolarization temperature Td = 465 °C. The BLT addition concentration may modify the aforementioned BF-BT ceramic structures and properties, while the decrease of sintering temperature from 960 °C to 880 °C causes modest decreases of relative density of BF-BT-0.0072BLT ceramics from 94.73% to 93.56% and d33 from 146 pC/N to 135 pC/N. Enhanced piezoelectric properties of d33 = 135 pC/N, kp = 0.279, and Qm = 63.713 are obtained for BF-BT-0.0072BLT ceramic even at an extremely low sintering temperature of 880 °C. In addition, the d33 of BF-BT-0.0012BLT ceramic reached 392 pC/N at 352 °C by in-situ dynamic d33 testing. This indicates the piezoelectric properties of the piezoelectric ceramic in its actual operating state. The main novelty of this study is the relatively high piezoelectric properties obtained at low sintering temperature and the d33 reaching 392 pC/N at 352 °C. The findings suggest that the ceramic is a viable material for the use of lead-free piezoelectric ceramics.

Effect of Bi3+ and Ti4+ substitution on PbNb2O6 piezoelectric ceramics

In this study, Pb1-2xBi2x(Nb1-xTix)2O6 (PBNTx, x = 0.02–0.08) ceramics with tungsten bronze structure were prepared via the solid-state reaction method. Single orthorhombic ferroelectric phase was detected for all PBNTx ceramics. SEM results indicated fully densified morphology for the samples of x ≥ 0.06. Optimal piezoelectric performance was obtained at the sample of x = 0.08, whose piezoelectric constant (d33) reached to 92 pC/N and Curie temperature (Tc) was up to 593 °C. A notably high electromechanical coupling coefficient (kp) greater than 0.6 was also obtained in this system. The improved piezoelectric performance indicated that Bi3+ and Ti4+ modified PbNb2O6 system is promising for ultrasonic defect detection and transducer applications at high temperatures.

Enhanced piezoelectric activity around orthorhombic-tetragonal phase boundary in multielement codoping BaTiO3

Lead-free piezoelectric ceramics (Ba1-xCax)(Ti0.97Zr0.01Sn0.01Ce0.01)O3 (x = 0, 0.0125, 0.025, 0.0375, 0.05, 0.075, 0.1) have been prepared by conventional solid-reaction method. X-ray diffraction and variable temperature dielectric measurements confirm the coexistence of orthohombic and tetragonal phase near room temperature at x = 0.025. With the presence of the polycrystalline phase transitions (PPT) effect, the ceramic with x = 0.025 demonstrates an excellent electrical property with piezoelectric coefficient d33 of 523 pC/N, planar electromechanical coupling coefficient kp of 49% and strain of 0.093%.

SnO2 modified PNN-PZT ceramics with ultra-high piezoelectric and dielectric properties

In this work, a two-step solid-state reaction method is used to prepare the 0.55 Pb(Ni1/3Nb2/3)O3-0.135PbZrO3-0.315PbTiO3/xSnO2 (PNN-PZT/xSnO2) ceramics. The influences of SnO2 on the crystalline structure, electromechanical properties, and temperature stability of PNN-PZT ceramics were studied in detail. The results demonstrate that the Sn4+ ions are successfully introduced into the PNN-PZT crystalline lattice and substitute B-site Ni2+ and Zr4+. The x = 0.0025 ceramic with the coexistence of rhombohedral, tetragonal, and pseudocubic phases exhibits the optimized comprehensive properties: the quasi-static piezoelectric constant d33, large-signal d33*, electromechanical coupling coefficients kp and kt, free dielectric constant εr, and mechanical quality factor Qm are 1123 pC/N, 1250 p.m./V, 0.63, 0.54, 9529, and 57, respectively. Meanwhile, the Curie temperature for this composition is 103 °C, almost maintaining the same level as the PNN-PZT matrix. After annealing at 75 °C, the retained d33 of x = 0.0025 ceramic is as high as 975 pC/N, superior to the PNN-PZT matrix (retained d33 ≈ 873 pC/N). Our results provide a promising piezoelectric material for board bandwidth, high sensitivity, and miniaturized medical ultrasonic transducers applications.

Preparation, Structure, and Electrical Properties of Cobalt-Modified Bi(Sc3/4In1/4)O3-PbTiO3-Pb(Mg1/3Nb2/3)O3 High-Temperature Piezoelectric Ceramics.

Cobalt-modified 0.40Bi(Sc3/4In1/4)O3–0.58PbTiO3–0.02Pb(Mg1/3Nb2/3)O3 ceramics (abbreviated as BSI–PT–PMN–xCo) were produced by conventional two-step solid-state processing. The phase structure, micro structure morphology, and electrical properties of BSI–PT–PMN–xCo were systematically studied. The introduction of Co ions exerted a significant influence on the structure and electrical properties. The experiment results demonstrated that Co ions entered the B-sites of the lattice, resulting in slight lattice distortion and a smaller lattice constant. The average grain size increased from ~1.94 μm to ~2.68 μm with the increasing Co content. The optimized comprehensive electrical properties were obtained with proper Co-modified content 0.2 wt.%. The Curie temperature (Tc) was 412 °C, the piezoelectric constant (d33) was 370 pC/N, the remnant polarization (Pr) was 29.2 μC/cm2, the relatively dielectric constant (εr) was 1450, the planar electromechanical coupling coefficient (kp) was 46.5, and the dielectric loss (tanδ) was 0.051. Together with the enhanced DC resistivity of 109 Ω cm under 300 °C and good thermal stability, BSI–PT–PMN–0.2Co ceramic is a promising candidate material for high-temperature piezoelectric applications.

Enhanced piezoelectric properties of Sm3+-modified PMN-PT ceramics and their application in energy harvesting

Piezoelectric materials are widely used in electromechanical energy conversion, such as in sensors, transducers, and self-powered materials. In this paper, the influence of the Sm doping content on the microstructure and ferroelectric, piezoelectric, dielectric, and field-induced strain properties of 0.70Pb(Mg1/3Nb2/3)O3-0.30PbTiO3 (PMN-PT) ceramics was investigated. Sm-doped PMN-PT ceramics with both high piezoelectric properties (d33∼1406 pC/N) and a large electromechanical coupling coefficient (kp∼0.69) were synthesized. Based on their piezoelectric effect, a maximum output voltage of 31 V was achieved under external forces. The output voltages showed satisfactory stability, repeatability, and sensitivity under periodic external forces; hence, Sm-doped PMN-PT piezoelectric ceramics are potential candidates for energy conversion and signal monitoring.