Crystal structure and piezoelectric characteristics of various phases near the triple-point composition in PZ-PT-PNN system

Crystal structures and piezoelectric properties of PbZrO₃-PbTiO₃-Pb(Ni_1/3Nb_2/3)O₃ ceramics near the triple point composition, particularly characteristics of the pseudocubic phase, were investigated. The pseudocubic phase, which formed near the triple point composition, disappeared with increase in the PbZrO₃ content. The pseudocubic phase had the Pm3m cubic structure. The tetragonal-pseudocubic morphotropic phase boundary (MPB) structure was developed during the tetragonal-to-cubic phase transformation. However, the rhombohedral phase directly transformed to the cubic phase because the structure of pseudocubic phase was similar to the rhombohedral structure. The specimens with pseudocubic phase and the specimens near pseudocubic phase exhibited nano-sized domains and small coercive electric fields, revealing their low domain wall energies. These specimens exhibited second-order ferroelectric-to-paraelectric phase transition and low Curie temperatures, confirming their low domain wall energies. The enhanced dielectric and piezoelectric properties of these specimens could be attributed to their low domain wall energies.     

Ferroelectric,upconversion emission and optical thermometric properties of color-controllable Er3+-doped Pb(Mg1/3Nb2/3)O3-PbTiO3-Pb(Yb1/2Nb1/2)O3 ferroelectrics

The (0.98-x)(0.6Pb(Mg_1/3Nb_1/3)O₃-0.4PbTiO₃)-xPb(Yb_1/3Nb_1/3)O₃-0.02Pb(Er_1/2Nb_1/2)O₃ ((0.98-x)(PMN-PT)-xPYN:Er³⁺) ceramics were prepared through a solid-state reaction method. The phase structure, piezoelectric response, ferroelectric performance and upconversion emission of the ceramics were systematically investigated. The phase structure, the electrical and optical properties are strongly related to the content of PYN. The optimized piezoelectric response and upconversion emissions of the ceramics were achieved near x = 0.12, which locates in the morphotropic phase boundary (MPB) composition. Furthermore, the temperature sensing behaviors of the resultant compounds based on the thermally coupled levels of ²H_11/2 and ⁴S_3/2 of Er³⁺ ions in the temperature range of 133–573 K were studied by utilizing the fluorescence intensity ratio technique. Additionally, the thermal effect, which is induced by the laser pump power, of the studied ceramics is also investigated and the produced temperature is enhanced from 268 to 348 K with the pump power rising from 109 to 607 mW.     

Temperature-dependent piezoelectric strain and resonance performance of Fe2O3-modified BiScO3-PbTiO3-Pb(Nb1/3Mn2/3)O3 ceramics

The piezoelectric strain and resonance performance of 0.37BiScO₃-0.6PbTiO₃-0.03Pb(Mn_1/3Nb_2/3)O₃ (BS-PT-PMN-xFe) ceramics with different amounts of Fe content addition were investigated from room temperature to 200 °C. Both the piezoelectric strain and resonance performance are improved by Fe addition in wide temperature range. Piezoelectric strain of BS-PT-PMN-xFe with 1 mol% Fe is 0.23%, which is comparable to that of BiScO₃-PbTiO₃ (BS-PT) ceramics, while the strain hysteresis is only one-third. At 200 °C, the high-field strain coefficient of BS-PT-PMN-Fe with 1 mol% Fe is as large as 700 pm/V. Variation of piezoelectric strain and hysteresis is clearly reducing by Fe addition. The maximum vibration velocity is enhanced up to approximately 1 m/s in 2 mol% Fe-modified BS-PT-PMnN-xFe ceramics, and the vibration velocity is stable from room temperature to 200 °C when the electric voltage magnitude was below 60 V_pp. These results indicate that BS-PT-PMN-xFe ceramics are potential candidates for high-temperature piezoelectric actuator application.     

Structural and electrical properties of ZnO-modified (1−x)Pb(Mg1/3Nb2/3)O3−xPbTiO3 ceramics with wide MPB regions

Ferro-/piezoelectric ceramics with high performances are generally found at the morphotropic phase boundary (MPB), where two or more different ferroelectric phases coexist. However, the MPB region is usually very narrow; for example, that of (1−x)Pb(Mg_1/3Nb_2/3)O₃−xPbTiO₃ (PMN-xPT) locates between x = 0.30−0.34. Herein, we report that ZnO-modified PMN-xPT polycrystalline ceramics have dramatically broadened MPB regions from x = 0.28, with rhombohedral and monoclinic coexisting phases, to x = 0.36, with tetragonal and monoclinic coexisting phases, as confirmed by powder X-ray diffraction and piezoresponse force microcopy measurements. The wide MPB region is attributed to lattice distortion caused by the substitution of Zn for Mg cations. As a result, the ceramics show composition insensitive electrical properties over wide composition ranges; for example, the piezoelectric coefficient (d₃₃) and electromechanical coupling factor (k_p) remain at near constant values of 450 pC/N and 0.5, respectively, in the range from x = 0.28−0.34. This work not only provides a robust and feasible method to broaden the MPB region but also offers some novel insights into promoting fundamental research on high-performance piezoelectric ceramics.     

BiFeO3-PbZrO3-PbTiO3 ternary system for high Curie temperature piezoceramics

BiFeO₃-PbZrO₃-PbTiO₃ ternary solid solution system was investigated for the development of piezoelectric ceramics with high Curie temperatures. The search for the morphotropic phase boundary (MPB) compositions in this ternary system started from mixing two MPB compositions: 0.70BiFeO₃-0.30PbTiO₃ and 0.52PbZrO₃-0.48PbTiO₃. The content of PbTiO₃ was then further fine tuned in order to reach the appropriate volume fraction between the rhombohedral and tetragonal phases in the sintered ceramics. It was observed that the sintering temperature has a profound impact on the density, grain morphology, dielectric and ferroelectric properties of the ceramics. The composition that displays the best combined structure and properties was identified to be 0.648BiFeO₃-0.053PbZrO₃-0.299PbTiO₃, with a Curie temperature T_C of 560 °C, a remanent polarization P_r of 15.0 μC/cm², and a piezoelectric coefficient d₃₃ of 64 pC/N.     

Ultralow dielectric loss of BiScO3-PbTiO3 ceramics by Bi(Mn1/2Zr1/2)O3 modification

BiScO₃-PbTiO₃ ceramics are attractive for high-temperature piezoelectric applications while their high dielectric loss has to be substantially reduced. In this paper, a ternary perovskite system of xBi(Mn_1/2Zr_1/2)O₃-(1-x-y)BiScO₃-yPbTiO₃ (abbreviated as xBMZ-BS-yPT) with x = 0.02, 0.04 and y = 0.62–0.67 were fabricated by conventional solid-phase method, and their ceramics were systematically studied with regards to phase structure, microstructure, dielectric and piezoelectric properties. X-ray diffraction results indicate a gradual change from rhombohedral to tetragonal phase with increasing PT composition. Morphotropic phase boundary (MPB) is revealed for the system with x = 0.02, y = 0.64, at which ultralow dielectric loss factor (0.58 %), almost unchanged Curie temperature (449 °C), high electromechanical properties (d₃₃ = 360 pC/N, k_p = 0.53), and stable strain output below 200 °C are observed. With such excellent piezoelectric properties and high-temperature stability, BMZ modified BS-PT ceramics are promising candidates for power electromechanical devices, especially operating in high-temperature environments.     

Achieving both large piezoelectric constant and high Curie temperature in BiFeO3-PbTiO3-BaTiO3 solid solution

The high-temperature and high-performance piezoelectric ceramics are required urgently in the petrochemical, automotive, and aerospace industries. In this work, the (0.85-x)BiFeO₃-xPbTiO₃-0.15BaTiO₃ (BF-PT-BT, x = 0.21, 0.22, 0.23, 0.24 and 0.25) piezoelectric ceramics with both high Curie temperature and large piezoelectric constant d₃₃ were presented. X-ray diffraction analysis shows that BF-PT-BT ceramics exhibit dominant perovskite structure with the coexistence of tetragonal (T) and rhombohedral (R) phases. The c/a ratio, Curie temperature, piezoelectric constant, dielectric constant and loss of the BF-PT-BT ceramics for x = 0.23 are 1.06, 546 °C, 222 pC/N, 545 and 0.013, respectively. Room temperature piezoelectric constant of BF-PT-BT ceramics is much higher than those of PbTiO₃, PbNb₂O₆ and other ABO₃ perovskite compounds (BaZrO₃, Bi(Zn, Ti)O₃, PbZrO₃ and Pb(Mg, Nb)O₃) modified ternary BiFeO₃-PbTiO₃ ceramics with similar Curie temperatures. The piezoelectric constant is almost unchanged after BF-PT-BT ceramics was annealed at 450 °C for 30 min, which is due to the stable switched non-180° domain and transformed R phase by annealing treatment.     

Correlation between structural,ferroelectric, piezoelectric and dielectric properties of Ba0.7Ca0.3TiO3-xBaTi0.8Zr0.2O3 (x = 0.45, 0.55) ceramics

We report on the correlation between structural, ferroelectric, piezoelectric and dielectric properties of the (1-x)Ba_0.7Ca_0.3TiO₃-xBaTi_0.8Zr_0.2O₃ (x?=?0.45, 0.55; abbreviated as 55BCT30 and 45BCT30) ceramics close to morphotropic phase boundary (MPB) region. The 55BCT30 and 45BCT30 ceramics were synthesized by the standard, high-temperature solid state ceramic method. X-ray diffraction (XRD) along with Rietveld refinement indicate that the 55BCT30 ceramics exhibit rhombohedral (R, space group R3m), orthorhombic (O, space group Amm2) and tetragonal (T, space group P4mm) phases while 45BCT30 ceramics exhibit only T and O phases. The temperature dependent Raman spectroscopy measurements confirm the structure and phase transformations observed from XRD. All the ceramics are chemically homogeneous and exhibit a dense microstructure with a grain size of 5–7?µm. The presence of polarization-electric field and strain-electric field hysteresis loops confirm the ferroelectric and piezoelectric nature of the ceramics. The polarization current density-electric field curves show the presence of two sharp peaks in opposite directions indicating the presence of two stable states with opposite polarity. Higher values of direct piezoelectric coefficient (d₃₃ ~?360 pC/N) were observed due to the existence of low energy barrier near MPB region and polymorphism. The 55BCT30 ceramics exhibit a higher value of electrostrictive coefficient (Q₃₃ ~?0.1339?m⁴/C²) compared to the well-known lead-based materials. The temperature dependent dielectric measurements indicate the O to T phase transition for 55BCT30 and 45BCT30. These ceramics exhibit a Curie temperature (T_c) of 380?K with a dielectric maximum of ~ 4500.     

Phase transitions in (1−x)BaZr0.2Ti0.8O3−xBa0.7Ca0.3TiO3 powders and ceramic pellets

The phase transitions in (1−x)BaZr_0.2Ti_0.8O₃−xBa_0.7Ca_0.3TiO₃ (BZT-xBCT) powders and ceramic pellets were studied. It is found that the phase compositions in the pellets are different from that in the powders, which may be caused by the stress in the pellets. The monoclinic phase exists near the morphotropic phase boundary (MPB) in the ceramics. The piezoelectric coefficient (d₃₃) measurement of the ceramics shows that the higher piezoelectric properties are corresponding to higher content of monoclinic phase.     

High electric field-induced strain properties in La-doped Pb(In1/2Nb1/2)O3–PbZrO3–PbTiO3 relaxor ferroelectric ceramics

Piezoelectric ceramics with high strain response and low hysteresis are highly in demand for high-performance actuator applications. Unfortunately, the trade-off relationship between large field-induced strain and low hysteresis in piezoelectric ceramics is a key challenge for designing high-performance piezoelectric actuators. Herein, ymol%La-doped 0.10 Pb(In_1/2Nb_1/2)O₃-xPbZrO₃-(0.90–x)PbTiO₃ [0.10PIN-xPZ-(0.90-x)PT: ymol%La] ternary relaxor ferroelectric ceramics were prepared by conventional solid-state reaction technique. Pb(In_1/2Nb_1/2)O₃ (PIN) as a relaxor end member was introduced into (Pb,La) (Zr,Ti)O₃ (PLZT) system to improve relaxor characteristics and strain properties. A giant strain of 0.23% was obtained in 0.10PIN-0.59PZ-0.31 PT: 8mol%La ceramic at the electric field of 20 kV/cm, with a high piezoelectric d₃₃* of 1150 pm/V and low hysteresis H_y of 6.4%, exhibiting a potential application in high-performance piezoelectric actuators. Furthermore, the effects of La ion doping and components on the ferroelectric, dielectric and electric field-induced strain properties were investigated, and provides a new way for improve the strain properties of piezoelectric materials.     

Lead-reduced Bi(Ni2/3Ta1/3)O3-PbTiO3 perovskite ceramics with high Curie temperature and performance

With increasing demand of high-temperature piezoelectric devices and growing concern over environment protection, a feasible reduction in lead from lead-based high Curie temperature piezoelectric materials are desperately needed. Herein, a new system of lead-reduced Bi(Ni_2/3Ta_1/3)O₃-PbTiO₃ (BNT-PT) ferroelectric ceramics is fabricated by a conventional solid-state sintering process. The phase transition behaviors as a function of composition and temperature, electrical properties, as well as the domain configurations from a microscopic level have been investigated in detail. The results indicate that crystal structures, phase transition behaviors, and electric properties of BNT-PT ceramics can be affected significantly by the content of BNT counterpart. Dielectric measurements show that xBNT-(1−x)PT ceramics transfer from the normal ferroelectrics to the relaxor ferroelectrics at compositions of x = 0.3-0.35. The BNT-PT ceramics exhibit high Curie temperature T_C ranging from 474 to 185°C with the variation in BNT content. The relative dielectric tunability n_r also rises from only 0.65% for 0.10BNT-0.90PT to 50.23% for 0.40BNT-0.60PT with increasing BNT content. The tetragonal-rich composition 0.30BNT-0.70PT ceramic possesses the maximum remnant polarization of P_r ~ 34.9 μC/cm². Meanwhile, a highest piezoelectric coefficient of d₃₃ ~ 271 pC/N and a high field piezoelectric strain coefficient of  ~ 560 pm/V are achieved at morphotropic phase boundary (MPB) composition of 0.38BNT-0.62PT. The maximum value of strain ~0.31% is obtained in the 0.36BNT-0.64PT ceramic. The largest electromechanical coupling coefficient k_p is 44.5% for 0.37BNT-0.63PT ceramic. These findings demonstrate that BNT-PT ceramics are a system of high-performance Pb-reduced ferro/piezoelectrics, which will be very promising materials for piezoelectric devices. This study offers an approach to developing and exploring new lead-reduced ferroelectric ceramics with high performances.     

Effects of sintering temperature and KBT content on microstructure and electrical properties of (Bi.5Na.5)TiO3-BaTiO3-(Bi.5K.5)TiO3 Pb-free ceramics

A route exploring the morphotropic phase boundaries (MPB) region in (Bi_.5Na_.5)TiO₃-BaTiO₃-(Bi_.5K_.5)TiO₃ ternary system has been designed based on the phase diagram. X-ray diffraction (XRD) has been performed to determine the phases of the prepared samples. The dielectric, ferroelectric, and piezoelectric properties of [(1-x) 0.9363(Bi_.5Na_.5)TiO₃–0.0637BaTiO₃]-x(Bi_.5K_.5)TiO₃ (BNKBT100x) ternary lead-free piezoelectric ceramics are investigated as the functions of x and sintering temperature. When x was varied from 0 to 0.11, the BNKBT100x ceramics show single perovskite structure sintered at 1130–1210?°C. These ceramics show large dielectric permittivity, small dielectric loss, and diffused phase transition behavior. Well-defined ferroelectric polarization-electric field (P-E) hysteresis loop and relative large piezoelectric and electromechanical coefficients are also found in these ceramics. When increasing x, the electrical performances first increase, then decrease. The same rule is found when varying the sintering temperature. The optimized composition and sintering temperature are finally obtained.     

Giant piezoelectric coefficient of PNN-PZT-based relaxor piezoelectric ceramics by constructing an R-T MPB

xTa-PNN-PZT piezoelectric ceramics with [0.55 Pb(Ni_1/3Nb_2/3)O₃ - 0.45 Pb(Zr_0.3Ti_0.7)O₃ - xwt%Ta₂O₅] + 1 wt% PbO composition (0 ≤ x ≤ 0.7) were prepared by conventional solid-state reaction method. Special attention was paid to the effect of Ta₂O₅ concentration on structural, dielectric, piezoelectric, and ferroelectric properties of these ceramics. In particular, rhombohedral-tetragonal morphotropic phase boundary was observed in PNN-PZT crystal structure near the composition of x = 0.5. At this point, volume fraction of rhombohedral phase was almost equal to that of tetragonal phase. In addition, the ceramic exhibited the optimum values of piezoelectric coefficient, bipolar strain, unipolar strain, and inverse piezoelectric coefficient, i.e., 1090 pC/N, 0.135%, 0.165%, and 1493 pm/V, respectively. Moreover, according to in-situ X-ray diffraction, piezoelectric force microscopy, and in-situ strain measurement results, phase structure of 0.5Ta-PNN-PZT revealed relatively stable piezoelectric behavior at 60 °C.     

Electromechanical properties of Mn-doped Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 piezoelectric ceramics

The dielectric, piezoelectric, and ferroelectric properties of Mn-doped and undoped yPb(In_1/2Nb_1/2)O₃-(1−x−y)Pb(Mg_1/3Nb_2/3)O₃-xPbTiO₃ (PIN-PMN-PT) ternary ceramics with morphotropic phase boundary composition have been investigated. Mn-doped PIN-PMN-PT ceramics show obvious hardening characteristics. With 2 mol% Mn doping the mechanical quality factor Q_m can be increased to as high as 2000, while the electromechanical coupling factor (k_p=57%) is still comparable to that of the undoped counterpart. The internal bias field E_i was analyzed and calculated based on the P-E hysteresis loops for the Mn-doped PIN-PMN-PT ceramic. The relatively high Curie temperature, very high Q_m, and low dielectric loss make the Mn-doped PIN-PMN-PT ceramics good candidates for high power and high temperature electromechanical device applications.     

Phase transition,microstructure, and dielectric properties of Li/Ta/Sb co-doped (K,Na)NbO3 lead-free ceramics

Li/Ta/Sb co-doped lead-free (K_0.4425Na_0.52Li_0.0375)(Nb_0.93−xTa_xSb_0.07)O₃ (abbreviated KNLNST_x) piezoelectric ceramics, with Ta-doping ratio of x ranging from 0.0275 to 0.0675, were synthesized using the conventional solid-state reaction method at the sintering temperature of 1130 °C. The effects of Ta content on the microstructure, dielectric properties, and phase transition behavior of the prepared ceramics were systematically investigated. The X-ray diffraction results show that all KNLNST_x ceramics formed a secondary phase, which is assigned to the tetragonal tungsten-bronze type (TTB) structure phase, and showed a phase transition from an orthorhombic symmetry to a tetragonal symmetry across a composition region of 0.0375<x<0.0475. The grain shape and size that correspond to the phase structure transformations can be clearly observed in the scanning electron microscopy images. As x increased to 0.0475, the KNLNST_0.0475 ceramics changed from orthorhombic to tetragonal structure and showed excellent piezoelectric properties of d₃₃=313 pC/N, k_p=47%, and ε_r=1825. By contrast, samples of x=0.0375 with orthorhombic symmetry exhibited poor piezoelectric properties, with d₃₃=200 pC/N and ε_r=1015. These results indicate that phase structure is vital in the piezoelectric properties of KNN lead-free ceramics.     

Enhanced ferroelectric,magnetic and magnetoelectric properties of multiferroic BiFeO3–BaTiO3–LaFeO3 ceramics

A lead–free multiferroic ceramic 0.7BiFeO₃–0.3BaTiO₃ showed strong ferroelectric and piezoelectric properties, but weak magnetic and magnetoelectric properties. We herein expected that the electrical and magnetic properties of 0.7BiFeO₃–0.3BaTiO₃ ceramics could be enhanced by introducing LaFeO₃. (0.7–x) BiFeO₃–0.3BaTiO₃–xLaFeO₃ (x?=?0–0.2) were synthesized by solid-state reaction. All the ceramics formed a perovskite structure, and a morphotropic phase boundary (MPB) between rhombohedral and orthorhombic phases formed at x?=?0.025. The ceramics with MPB composition had high unipolar strain (S_max = 0.14%), piezoelectricity (d₃₃ = 223 pC/N, d₃₃ * = 350?pm/V), ferroelectricity (P_r = 25.67 mC/cm²) and magnetoelectricity (a_ME = 466.6?mV/cm·Oe), which can be attributed to addition of La ions. The improved phase angle also demonstrated augmentation of ferroelectricity on the microscopic view. The ferromagnetism was evidently improved after LaFeO₃ doping, and the remanent magnetization M_r increased from 0.0207 to 0.0622?emu/g with rising x from 0 to 0.075. In conclusion, with strong magnetoelectric properties, the prepared ceramics may be applicable as promising lead–free multiferroic ceramic materials for novel electronic devices.     

Remarkable piezoelectric activity and high electrical resistivity in Cu/Nb co-doped Bi4Ti3O12 high temperature piezoelectric ceramics

Cu/Nb co-doped Aurivillius type Bi₄Ti_3-x(Cu_1/3Nb_2/3)_xO₁₂ (BTCN) ceramics were investigated as a potential candidate for high temperature piezoelectric application. The microstructure, phase structure and resulting piezoelectric properties and conduction behaviors were systematically investigated. A remarkable d₃₃ of 38 pC/N was achieved in the ceramic with a composition of x = 0.015, which may be ascribed to the enhancement of remanent polarization and decrease of coercive field. Moreover, a high DC resistivity of 8.39 × 10⁶ Ω·cm at 500 °C was also obtained in the composition, due to the decrease of the oxygen vacancy concentration induced by the doped Cu/Nb. Furthermore, the ceramic also exhibited stable thermal annealing behaviors and excellent fatigue resistance. All the results demonstrated the great potential of the Cu/Nb co-doped Bi₄Ti₃O₁₂ ceramics for high temperature piezoelectric applications.     

Investigation of dielectric and piezoelectric properties in Pb(Ni1/3Nb2/3)O3–PbHfO3–PbTiO3 ternary system

The dielectric and piezoelectric properties were investigated in the (1 ? x)Pb(Hf_1?yTi_y)O₃–xPb(Ni_1/3Nb_2/3)O₃ (PNN–PHT, x = 0.05–0.50, y = 0.55–0.70) ternary system. The morphotropic phase boundary (MPB) was determined by X-ray powder diffraction analysis. Isothermal map of Curie temperature (T_C) related to the compositions in the phase diagram was obtained. The optimum dielectric and piezoelectric properties were achieved in ceramics with the MPB compositions, with the maxima values being on the order of 6000 and 970pC/N, respectively. Rayleigh analysis was used to study the extrinsic contribution (domain wall motion) in PNN–PHT system, where the extrinsic contribution was found to be ～30% for composition 0.49PNN–0.51PHT(30/70), showing a high nonlinearity.     

Investigation of dielectric and piezoelectric properties in aliovalent Eu3+-modified Pb(Mg1/3Nb2/3)O3-PbTiO3 ceramics

Rare earth (Eu³⁺)-modified Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (PMN-PT) polycrystalline ferroelectric ceramics were fabricated by high-temperature solid-state sintering, the phase structure, dielectric and piezoelectric properties were investigated. Eu³⁺ addition was found to significantly improve dielectric and piezoelectric properties of PMN-PT, where the optimized properties were achieved for the composition of 2.5 mol%Eu: 0.72PMN-0.28PT, with the piezoelectric d₃₃ = 1420 pC/N, dielectric ε_r = 12 200 and electromechanical k₃₃ = 0.78, respectively. All these results indicate that the Eu³⁺-doped PMN-PT ceramics are promising candidates for high-performance room-temperature piezoelectric devices.