Processing and electrical properties of (1 − x)[(1 − y)(Pb(Mg1/3Nb2/3)O3)–y(Pb(Yb1/2Nb1/2)O3)]–xPbTiO3 ceramics

Ferroelectric ceramics in the vicinity of morphotropic phase boundary (MPB) with compositions represented as (1 ? x)[(1 ? y)(Pb(Mg_1/3Nb_2/3)O₃)–y(Pb(Yb_1/2Nb_1/2)O₃)]–xPbTiO₃ were prepared by solid state reaction. The addition of PYbN to PMN–PT decreased the sintering temperature from 1200 °C (y = 0.25) to 1000 °C (y = 0.75). The PT content, where the MPB was observed, increased with the PYbN addition. A remanent polarization value of 28.5 µC/cm² and a coercive field value of 11 kV/cm were measured from 0.62[0.25PMN–0.75PYbN]–0.38PT ceramics, which were close to the ones measured from PMN–0.32PT ceramics. In addition, the Curie temperature was found to increase with PYbN additions.     

Diffuse transition and piezoelectric properties of Pb[(Zr1−xTix)0.74(Mg1/3Nb2/3)0.20(Zn1/3Nb2/3)0.06]O3 Ceramics

In this work, the piezoelectric ceramic system of Pb[(Zr_1−xTi_x)_0.74(Mg_1/3Nb_2/3)_0.20(Zn_1/3Nb_2/3)_0.06]O₃, 0.47≤x≤0.57, with composition close to the morphotropic phase boundary, was studied. From the results of X-ray diffraction and piezoelectric measurement, ceramics near x=0.51 were found at the morphotropic phase boundary (MPB) between the tetragonal and pseudocubic perovskite. The planar coupling factor (k_p=0.72) is high at compositions near the MPB, but the mechanical quality factor (Q_m=75) is low. The calculation of the diffuseness of phase transition shows that the region of phase coexistence of this system is broader than that of the ternary system.     

Phase equilibria and electrical properties of barium-containing relaxor-based solid solutions

We have studied the effect of modification with Ba on the phase composition, structure, and electrical properties of ceramic samples of Pb_(1?x)Bax(Mg_1/3Nb_2/3) _m (Zn_1/3Nb_2/3) _y (Ni_1/3Nb_2/3) _n Ti _z O₃ (0 ≤ x ≤ 0.15) solid solutions and investigated phase equilibria in this system in the range 0 ≤ x ≤ 0.15. The results indicate that a tetragonal and a low-symmetry phase coexist in the composition range 0 ≤ x ≤ 0.05, a pseudocubic phase exists in the range 0.05 < x < 0.10, and a cubic phase exists in the range 0.1 ≤ x ≤ 0.15. We propose a scheme of solid-solution formation according to which partial barium substitution for lead in the range 0 ≤ x ≤ γ (where γ is structural nonstoichiometry) causes the Pb ions to leave distorted octahedra. For x > γ, Ba²⁺ substitutes for Pb²⁺ on the cuboctahedral site. The sintering temperature is shown to influence the phase composition of the modified ceramics. We demonstrate, that varying the Ba content of the solid solutions, one can obtain a series of materials with a wide range of electrical parameters (?/?₀ = 2880–11000, K _p = 0.07–0.43, and Q _m = 48–8300) and potential applications in hydroacoustics, piezoelectric motors, and capacitor technology.     

Dielectric and Piezoelectric Properties of Pb(Mg1/3Nb2/3)O3–PbTiO3–Pb(Mg1/2W1/2)O3 Ceramics

Data are presented on the phase composition, crystal structure, microstructure, and dielectric and piezoelectric properties of (1 – y)[(1 – x)Pb(Mg_1/3Nb_2/3)O₃–xPbTiO₃]–yPb(Mg_1/2W_1/2)O₃ (x = 0.30–0.36; y = 0, 0.05, 0.10) ceramics. It is shown that the use of fine-particle magnesia as a starting reagent ensures the formation of single-phase materials. The ceramics with a rhombohedral structure are found to exhibit relaxor behavior. Increasing the content of the Pb(Mg_1/2W_1/2)O₃ perovskite leads to ordering of the domain structure of poled ceramics and increases their piezoelectric charge coefficient d ₃₁ and the width of their phase transitions.     

Electrical properties of non-stoichiometric PZT 95/5 ferroelectric ceramics

Pb_0.99(Zr_0.95Ti_0.05)_0.98Nb_0.02O₃ (denoted as PZT 95/5) ceramics were prepared according to the nominal composition of Pb_0.99+x (Zr_0.95Ti_0.05)_0.98Nb_0.02O_3+x (?0.01 ≤ x ≤ 0.04). The electrical properties as a function of lead oxide (Pb) stoichiometry were evaluated. X-ray diffraction analysis shows that all the as-synthesized PZT 95/5 powders are pure perovskite phase and the unit cell volume increases with the addition of Pb. SEM micrographs indicate the fracture mode tends to be predominately intergranular and grain size gets bigger with the increase of Pb content. The coercive field decreases with the increase of Pb till x = 0.02 and then increases when the excess Pb is over x = 0.02. The remnant polarization first increases and then decreases with the increasing amount of excess Pb. Sample with excess Pb x = 0.03 has the biggest value of remnant polarization.     

(Na0.5K0.5)NbO3–LiTaO3 lead-free piezoelectric ceramics

Lead-free piezoelectric ceramics were prepared in the system (1−x)(Na_0.5K_0.5)NbO₃–xLiTaO₃ following the conventional mixed oxide route. The effect of cationic substitution of lithium for sodium and potassium in the A sites and tantalum for niobite in the B sites in (Na_0.5K_0.5)NbO₃ (NKN) perovskite lattice on symmetry and physical properties were investigated. The materials with perovskite structure are in orthorhombic phase when x<5 mol.% and transform to tetragonal phase when x>6 mol.%; when x≥8 mol.%, a K₃Li₂Nb₅O₁₅ phase with tetragonal tungsten bronze structure begins to appear and becomes dominant with increasing content of LiTaO₃. A morphotropic phase boundary (MPB) between orthorhombic and tetragonal phases appears at x=5–6 mol.%. Analogous to Pb(Zr,Ti)O₃, the piezoelectric and electromechanical properties are enhanced for compositions near the morphotropic phase boundary. Piezoelectric constant d₃₃ values reach ∼200 pC/N. Electromechanical coefficients of planar mode reach ∼36%, respectively. Our results show that (Na_0.5K_0.5)NbO₃ with small amount of LiTaO₃ (x=7 mol.%) is a good lead-free piezoelectric ceramic.     

Effect of Pb(Fe1/2Nb1/2)O3 modification on dielectric and piezoelectric properties of Pb(Mg1/3Nb2/3)O3-PbZr0.52Ti0.48O3 ceramics

10 mol% Pb(Fe_1/2Nb_1/2)O₃ (PFN) modified Pb(Mg_1/3Nb_2/3)O₃-PbZr_0.52Ti_0.48O₃ (PMN-PZT) relaxor ferroelectric ceramics with compositions of (0.9 − x)PMN-0.1PFN-xPZT (x = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 and 0.9) were prepared. X-ray diffraction investigations indicated that as-prepared ceramics were of pure perovskite phase and the sample with composition of x = 0.8 was close to morphotropic phase boundary (MPB) between rhombohedral and tetragonal phase. Dielectric properties of the as-prepared ceramics were measured, and the Curie temperature (T_c) increased sharply with increasing PZT content and could be higher than 300 °C around morphotropic phase boundary (MPB) area. At 1 kHz, the sample with composition of x = 0.1 had the largest room temperature dielectric constant ?_r = 3519 and maximum dielectric constant ?_m = 20,475 at T_m, while the sample with composition of x = 0.3 possessed the maximum dielectric relaxor factor of γ = 1.94. The largest d₃₃ = 318 pC/N could be obtained from as-prepared ceramics at x = 0.9. The maximum remnant polarization (P_r = 28.3 μC/cm²) was obtained from as-prepared ceramics at x = 0.4.     

Comparative investigation of structure and dielectric properties of Pb(Mg1/3Nb2/3)O3-PbTiO3 (65/35) and 10% PbZrO3-doped Pb(Mg1/3Nb2/3)O3-PbTiO3 (65/35) ceramics prepared by a modified precursor method

Relaxor ferroelectric Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (65/35) and 10% PbZrO₃-doped Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (65/35) ceramics were both prepared by a modified precursor method, which was based on the high-temperature synthesis of an oxide precursor that contained all the B-site cations for the consideration of B-site homogeneity. The dielectric properties of Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (65/35) ceramic was more of normal ferroelectric behavior, but the high dielectric constant (?_m = 34,200 at 1 kHz) and piezoelectric constant (d₃₃ = 709 pC/N) were observed for this composition close to the morphotropic phase boundary. Comparatively, introduction of 10% PbZrO₃ into Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (65/35) ceramics enhanced the diffuse phase transition as well as the rhombohedral to tetragonal phase transition temperature, while it also kept the high dielectric constant (?_m = 29,600 at 1 kHz) and piezoelectric constant (d₃₃ = 511 pC/N).     

Dielectric and impedance spectroscopic studies of (Sr1−x Pb x )TiO2 glass ceramics with addition of Nb2O5

Glasses were made by melt-quench method in the system [(Sr_1?x Pb _x )O·TiO₂]-[2SiO₂·B₂O₃]-5[K₂O-BaO] (0·0 ≤ x ≤ 0·4) with addition of 1 mol% Nb₂O₅. Perovskite strontium lead titanate in solid solution phase has been crystallized in borosilicate glassy matrix with suitable choice of composition and heat treatment schedule. Addition of 1 mol% of Nb₂O₅ enhances the crystallization of lead strontium titanate phase in the glassy matrix. Scanning electron microscopy (SEM) is performed to study the surface morphology of the crystallites and crystalline interface to the glass. Dielectric properties of these glass ceramics were studied by measuring capacitance and dissipation factor as a function of temperature at a few selected frequencies. Nb₂O₅ doped strontium lead titanate glass ceramic shows a high value of dielectric constant. It is of the order of 10,000 while the dielectric constant of undoped glass ceramic sample is of the order of 500. Complex impedance and modulus spectroscopic techniques were used to find out the contributions of polarization of crystallites and glass crystal interfaces to the resulting dielectric behaviour.     

Structural characterization of 0.5PbMg1/3Nb2/3O3-0.5BaxPb(1−x)TiO3 powders

The present work reports the effects caused by barium on phase formation, morphology and sintering of lead magnesium niobate-lead titanate (PMN-50PT). Ab initio study of 0.5Pb(Mg_1/3Nb_2/3)O₃-0.5(Ba_xPb_(1−x)TiO₃) ceramic powders, with x = 0, 0.20, and 0.40 was proposed, considering that the partial substitution of lead by barium can reestablish the equilibrium of monoclinic-tetragonal phases in the system. It was verified that even for 40 mol% of barium, it was possible to obtain pyrochlore-free PMN-PT powders. The increase of the lattice parameters of PMN-PT doped-powders confirmed dopant incorporation into the perovskite phase. The presence of barium improved the reactivity of the powders, with an average particle size of 120 nm for 40 mol% of barium against 167 nm for the pure sample. Although high barium content (40 mol%) was deleterious for a dense ceramic, contents up to 20 mol% allowed 95% density when sintered at 1100 °C for 4 h.     

Investigation of phase diagram and electrical properties of xPb(Mg1/3Nb2/3)O3–(1 − x)Pb(Zr0.4Ti0.6)O3 ceramics

Ceramics in PMN–PZT system with formula xPb(Mg_1/3Nb_2/3)O₃–(1 ? x)Pb(Zr_0.4Ti_0.6)O₃ (where x = 0.32, 0.35, 0.38, 0.41) were prepared by the conventional oxide-mixed method. The phase diagram, composition dependent ferroelectric, dielectric, field-induced strain and piezoelectric properties were systematically investigated. X-ray diffraction analysis indicated that as-prepared ceramics were of pure perovskite phase and the possible morphotropic phase boundary (MPB) between the tetragonal and pseudo-cubic phase compositions were located near the PMN content of x = 0.38, confirmed by their corresponding ferroelectric, dielectric, field-induced strain and piezoelectric properties. The composition with x = 0.38 possessed the optimum electrical properties since its composition locate close to the MPB where exist multiple polarization directions facilitates domain reorientation and consequently enables the superior electrical properties. The room temperature dielectric permittivity ε _r , tangent loss tan δ, piezoelectric coefficient d ₃₃, electromechanical coupling factor kp, remnant polarization P _r , hysteresis loop squareness R _sq and longitudinal strain of 0.38PMN–0.62PZT ceramics are 2441, 2.08 %, 662 pC/N, 63.5 %, 37.2 μC/cm², 1.51 and 1.9 ‰, respectively, which mean it has a great promise for actuator applications.     

Phase formation, microstructure, and dielectric properties of (1 − x)PZT-(x)PCN ceramics

Ceramics in a PZT-PCN system with the formula (1 − x)Pb(Zr_1/2Ti_1/2)O₃-(x)Pb(Co_1/3Nb_2/3)O₃, where x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, and 1.0, were prepared using a solid-state mixed-oxide technique with columbite−CoNb₂O₆ and wolframite−ZrTiO₄ precursors. The crystal structure of the specimens studied with X-ray diffraction (XRD) analysis showed a coexistence between tetragonal and pseudo cubic phases at composition x = 0.2. The SEM micrograph showed that the average grain size significantly decreased with increasing PCN content. A maximum dielectric constant was observed at composition x = 0.2, while the transition temperature strongly decreased with increasing PCN content. All ceramics also showed diffused phase transition behaviors with a minimum diffusivity at x = 0.2. The morphotropic phase boundary (MPB) lay at the 0.8PZT-0.2PCN composition.     

Structure and electrical properties of Bi0.5Na0.5TiO3-Y0.5Na0.5TiO3-BaTiO3 lead-free piezoelectric ceramics

New (1 – x ? y)Bi_0.5Na_0.5TiO₃-xY_0.5Na_0.5TiO₃-yBaTiO₃ lead-free ceramics have been prepared by a conventional ceramic fabrication technique, and their structure and electrical properties have been studied. A morphotropic phase boundary (MPB) of rhombohedral and tetragonal phases is formed at 0.04 < y < 0.10. As compared to pure Bi_0.5Na_0.5TiO₃ ceramic, the partial substitutions of Y³⁺ for Bi³⁺ and Ba²⁺ for (Bi_0.5Na_0.5)²⁺ in the A-sites of Bi_0.5Na_0.5TiO₃ lower effectively the coercive field E _c and increase the remanent polarization P _r of the ceramics. Because of low E _c, large P _r and the MPB, the ceramics with x = 0–0.02 and y = 0.06 exhibit the optimum piezoelectric properties: d ₃₃ = 155–159 pC/N and k _p = 28.8–36.7%. The temperature dependences of dielectric properties of the ceramics show relaxor-like behaviors. The ferroelectric properties at different temperature suggest that the ceramics may contain both the polar and non-polar regions near/above T _d.     

Effect of BiFeO3 additions on the dielectric and piezoelectric properties of (K0.44Na0.52Li0.04)(Nb0.84Ta0.1Sb0.06)O3 ceramics

(1 − x) (K_0.44Na_0.52Li_0.04)(Nb_0.84Ta_0.1Sb_0.06)O₃ − x BiFeO₃ (x = 0, 0.002, 0.004, 0.006, 0.008, 0.01) lead-free piezoelectric ceramics were prepared by the conventional ceramic processing. The compositional dependence of the phase structure and the electrical properties of the ceramics were studied. A morphotropic phase boundary between the orthorhombic and tetragonal phases was identified in the composition range of 0.004 < x < 0.006. The ceramics near the morphotropic phase boundary exhibit a strong compositional dependence and enhanced piezoelectric properties. The ceramics with 0.6 mol.% BiFeO₃ exhibit good electrical properties (d₃₃ ∼ 246 pC/N, k_p ∼ 43%, T_c ∼ 285 °C, ?_r ∼ 1871, and tan δ ∼ 1.96%). These results show that the (1 − x) (K_0.44Na_0.52Li_0.04)(Nb_0.84Ta_0.1Sb_0.06)O₃ − x BiFeO₃ ceramic is a promising lead-free piezoelectric material for applications in different devices.     

Morphotropic phase boundary in Pb(Sc1/2Nb1/2)O3-BiScO3-PbTiO3 high temperature piezoelectrics

The solid solutions in the 0.36BiScO₃-0.64(1 − x)PbTiO₃-0.64xPb(Sc_1/2Nb_1/2)O₃ system were fabricated using wolframite precursor method. A coexistence of rhombohedral and tetragonal phases is formed in the studied compositions range and a wide morphotropic phase boundary region is confirmed by X-ray diffraction results. After the addition of Pb(Sc_1/2Nb_1/2)O₃, a relaxor behavior is induced and the dielectric maximum temperature shifts to higher temperatures with increasing measuring frequencies. The presence of relaxor can be ascribed to the formation of polar nanoregions. The studied composition exhibits the optimal ferroelectric and piezoelectric properties with d₃₃ of 453 pC/N and K_p of 0.58, T_m of 405 °C for x = 0.10 composition, which is suitable for future high-temperature piezoelectric application.     

Structural and microwave dielectric behavior of (Li1/4Nb3/4) substituted ZrxSnyTizO4 (x + y + z = 2) system

The phase structure, microwave dielectric properties, and their stability with different annealing conditions have been investigated in (Li_1/4Nb_3/4) substituted Zr_xSn_yTi_zO₄ system. The sintering temperature of Zr_xSn_yTi_zO₄ ceramic was lowered from 1500 to 1140 °C by (Li_1/4Nb_3/4) substitution. Both X-ray diffraction (XRD) analysis and electron diffraction (ED) analysis revealed that the (Li_1/4Nb_3/4) substituted Zr_xSn_yTi_zO₄ ceramic crystallized as the high-temperature disordered ZrTiO₄ phase. As the content of Sn increased from 0.10 to 0.30, the permittivity of the (Zr_1−xSn_x)(Li_1/4Nb_3/4)_0.4Ti_0.6O₄ ceramic decreased gradually from 35.5 to 31.5, the Q_f value increased from 37,800 to 58,300 GHz, and TCF value shifted slightly from −4.5 to −33.0 ppm °C⁻¹. Both the phase structure and microwave dielectric properties of (Zr_1−xSn_x)(Li_1/4Nb_3/4)_0.4Ti_0.6O₄ ceramics were stable with annealing conditions.     

Fabrication and properties of PYN-PMN-PZT quaternary piezoelectric ceramics for high-power, high-temperature applications

xPb(Yb_1/2Nb_1/2)O₃ - 0.05Pb(Mn_1/3Nb_2/3)O₃ - (0.95 - x)Pb(Zr_0.48Ti_0.52)O₃ (PYN-PMN-PZT) quaternary piezoelectric ceramics were prepared by a traditional ceramics process. The effects of Pb(Yb_1/2Nb_1/2)O₃ (PYN) content on the phase structure, electrical properties and Curie temperature of the quaternary system were investigated in detail. The phase structure of PYN-PMN-PZT ceramics changed from tetragonal to rhombohedral with increasing PYN content. The piezoelectric coefficient (d₃₃), the electromechanical coupling factor (K_p) and the dielectric constant (ε₃₃^T/ε₀) reach maximum values near the morphotropic phase boundary (MPB), whereas the mechanical quality factor (Q_m) decreases. The sintered PYN-PMN-PZT ceramics exhibit high T_C, and as the PYN content increases, T_C decreases slightly. The MPB of the tetragonal and rhombohedral phase coexist and are located at a PYN composition of 0.12 ≤ x ≤ 0.14.The composition of PYN-PMN-PZT around the MPB showed high d₃₃ (> 300pC/N), K_p (> 0.50), Q_m (> 1000) and T_C (> 350 °C), meaning it is a very promising piezoelectric material for high-power and high-temperature applications.     

Piezoelectric properties and aging mechanism of K0.5Na0.5Nb(1−y)Sb y O3 piezoceramics prepared by low temperature solvothermal method

K_0.5Na_0.5Nb_(1?y)Sb _y O₃ (KNNSy, y = 0.02–0.10) piezoceramics are obtained from the corresponding powder synthesized via a relatively low temperature solvothermal method. Crystalline structures and surface morphologies of these samples are analyzed by X-ray diffraction and scanning electron microscopy. The optimal sintering temperatures of KNNSy ceramics are controlled within 980–1,050 °C. The piezoelectric properties of the KNNSy ceramics are essentially affected by orthorhombic–tetragonal polymorphic phase transition. KNNS0.06 ceramic shows the maximum piezoelectric coefficient (d ₃₃) (134 pC/N). In addition, the aging behavior of KNNSy ceramics leads to the instability of their piezoelectric properties, which can be well explained according to defect symmetry conforming principle.     

Heterophase structures and their quantitative characteristics in (1 − x)Pb(Fe1/2Nb1/2)O3 − xPbTiO3 near the morphotropic phase boundary

Features of phase coexistence in solid solutions of (1 − x)Pb(Fe_1/2Nb_1/2)O₃ − xPbTiO₃ with the perovskite-type structure are studied at 0.05 ≤ x ≤ 0.08. The role of elastic matching of the tetragonal P4mm and monoclinic Cm phases of the ferroelectric nature is considered near the morphotropic phase boundary. Model concepts on the stress relief in heterophase structures are developed and applied to interpret the phase content in (1 − x)Pb(Fe_1/2Nb_1/2)O₃ − xPbTiO₃. Good agreement between the calculated and experimental dependences of the volume fraction of the tetragonal phase on x is observed. It is shown that the studied phase coexistence under conditions for the complete stress relief can take place at elastic matching of the single-domain monoclinic phase and the tetragonal phase split into two types of 90° domains.     

Structure,ferroelectric and piezoelectric properties of Bi0.5(Na0.8K0.2)0.5TiO3 modified BiFeO3–BaTiO3 lead-free piezoelectric ceramics

A new lead-free solid solution of (0.75 ? x)BiFeO₃–0.25BaTiO₃–xBi_0.5(Na_0.8K_0.2)_0.5TiO₃ + 1 mol% MnO₂ has been prepared by a conventional ceramic technique and the effects of Bi_0.5(Na_0.8K_0.2)_0.5TiO₃ and sintering temperature on the structure, ferroelectric and piezoelectric properties of the material have been studied. The ceramics sintered at 960 °C for 2 h possess a pure perovskite structure and no second phases can be detected. After the addition of Bi_0.5(Na_0.8K_0.2)_0.5TiO₃, a morphotropic phase boundary of rhombohedral and orthorhombic phases is formed at x = 0.01. The addition of a small amount of Bi_0.5(Na_0.8K_0.2)_0.5TiO₃ can promote the grain growth, while excess Bi_0.5(Na_0.8K_0.2)_0.5TiO₃ causes an inhibition of grain growth. Sintering temperature has an important influence on the structure and electrical properties of the ceramics. The sintering temperature of 960 °C is a critical temperature to obtain the ceramics with good piezoelectric properties. For the ceramic with x = 0.01 sintered at/above 960 °C located at the morphotropic phase boundary, large grains, good densification, high resistivity and enhanced electrical properties are obtained.