Low-temperature synthesis of chemically homogeneous lead zirconate titanate (PZT) powders by a semi-wet method

A semi-wet procedure for the synthesis of single-phase Pb(Zr _x Ti_1–x )O₃ powders at 600 °C is described. The ultrafine powders so obtained do not exhibit tetragonal/rhombohedral distortions until they are sintered at higher temperatures. The morphotropic phase boundary (MPB) for these powders, which are chemically homogeneous, lies between x=0.52 and 0.53. For x=0.525, the rhombohedral and tetragonal phases coexist.     

Enhanced ferro- and piezoelectric properties in (100)-textured Nb-doped Pb(ZrxTi1 − x)O3 films with compositions at morphotropic phase boundary

To develop high-performance piezoelectric films on conventional Pt(111)/Ti/SiO₂/Si(100) substrates, sol-gel-derived highly [100]-textured Nb-doped Pb(Zr_xTi_1 − x)O₃ (PNZT) thin films with different Zr/Ti ratios ranging from 20/80 to 80/20 were prepared and characterized. The phase structure, ferroelectric and piezoelectric properties of the PZNT films were investigated as a function of Zr/Ti ratios, and it was confirmed that there was distinct phase transition of the PNZT system from tetragonal to rhombohedral when the Zr/Ti ratio varied across the morphotropic phase boundary (MPB). The Nb-doped PZT films showed enhanced remanent polarization but reduced coercive field, whose best values reached 75 μC/cm² and 82 kV/cm, respectively at the composition close to MPB. In addition, the [100]-textured PNZT film at MPB also shows a high piezoelectric coefficient up to 161 pm/V. All these properties are superior to those for undoped PZT films.     

Development of PZT powders by wet chemical method and fabrication of multilayered stacks/actuators

Lead zirconate titanate (PZT) compositions near morphotropic phase boundary (MPB) Pb(Zr_xTi_1−x)O₃, 0.48≤ x ≤0.54, were prepared by wet chemical route using water soluble precursors. Compositions were prepared with donor dopants, such as La³⁺, Nd³⁺ or their combinations. The combined hydrous precursors were calcined in the temperature range of 750–900 °C. From the X-ray diffraction (XRD) patterns of calcined PZT powders, a change of tetragonal to rhombohedral phase was noticed with increase in zirconia concentration from 0.48 to 0.54 mol. Both rhombohedral and tetragonal phases were found in the composition range of 0.52–0.54 mol ratios of zirconia, therefore, this range was identified as MPB composition. Calcined PZT powders were compacted and sintered at 1250 °C/2 h in a closed lead rich atmosphere. The sintered compacts were leveled, polished, electroded and the ferroelectric and dielectric properties were measured. After poling, piezo properties were also measured. In case of undoped samples, it was observed that remnant polarization (P_r), dielectric constant (K) and piezoelectric charge constant (d₃₃) increase with zirconia concentration. In general, the above properties increase substantially by addition of dopants at low concentrations. The increase was found more for lanthanum doped samples compared to neodymium. The d₃₃ value for the combined dopants of lanthanum and neodymium was in between the values obtained for individual dopants of the same concentration. A few multilayered (25 layers) stacks were fabricated using thin strips cut from the sintered blocks of the above powders. The strips were electroded and poled in a dc field of 2 kV/mm and were laminated into multilayered stacks. The free strain of the multilayered stacks was measured by applying a dc voltage up to 650 V. The free strain was found to be linear and 0.1% of the height of the stack.     

Effect of lanthanum-doping on the dielectric and piezoelectric properties of PZN-based MPB composition

In this paper, effect of lanthanum doping on the dielectric and piezoelectric properties of the morphotropic phase boundary (MPB) composition in the Pb(Zn_1/3Nb_2/3)O₃-BaTiO₃-PbTiO₃ system is presented. Samples were prepared according to the formula Pb_0.85–x Ba_0.15La _x [(Zn_1/3Nb_2/3)_0.7Ti_0.3]_1–x/4O₃ (0 < x < 0.3), where the compensation for La ions was achieved via the appearance of B-site vacancies. All the compositions were synthesized using columbite precursor method and sintered using inverted crucible approach. Results of x-ray diffraction demonstrate that the solid solubility limit of La₂O₃ in the PZN-based MPB composition is more than 30 mole%. Incorporation of La₂O₃ into A-site sublattice of perovskite structure stabilizes rhombohedral phase against tetragonal phase, as a consequence, the location of the MPB composition range is displaced toward PT-rich end. In addition, the lattice distortion degree, represented by either tetragonality for tetragonal phase or rhombohedrality for rhombohedral phase, is reduced. Increasing La₂O₃ content remarkably decreases both the dielectric permittivity maximum and the temperature of the dielectric permittivity maximum. However, addition of La₂O₃ obviously strengthens the degree of the frequency-dispersion, which is correlated with the weakened degree of ferroelectric couplings among oxygen octahedra. The degree of diffuse phase transition (DPT) is prominently enhanced with increasing La₂O₃, for which the underlying mechanism is explored. Moreover, the ever-increasing extent of departure from Curie-Weiss behaviour induced by the lanthanum doping is indicative of some changes with the respect to the scale of polar microregions inherent to relaxors. The longitudinal piezoelectric coefficient (d ₃₃) is maximized at 1 mole% La₂O₃, which is attributed to the combined effect of phase coexistence and enhanced contribution from non-180° domain wall process associated with rhombohedral phase.     

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.     

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.     

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.     

Morphotropic phase boundary and electric properties in (1 − x)Bi0.5Na0.5TiO3–xBaSnO3 lead-free piezoelectric ceramics

Lead-free piezoceramics of (1 ? x)Bi_0.5Na_0.5TiO₃–xBaSnO₃ (BNT–BS, x = 0, 0.02, 0.03, 0.04, 0.06, 0.09 and 0.12) have been synthesized and investigated. A rhombohedral–tetragonal morphotropic phase boundary (MPB) exists near x = 0.03. The MPB composition shows improved electrical properties: the saturated polarization, remnant polarization, coercive field, piezoelectric coefficient, planar electromechanical coupling factor, and unipolar strain are 35.8, 28.5 μC/cm², and 4.5 kV/mm, 93 pC/N, 0.19, and 0.18 %, respectively. It is also found the introduction of BS can significantly enhance dielectric property. The structural and electrical properties are discussed by comparing with other BNT-based piezoceramics.     

The morphotropic phase boundary and electrical properties of (1?? x )Pb(Zn1/2W1/2)O3– x Pb(Zr0.5Ti0.5)O3 ceramics

Ceramics in the solid solution of (1 − x)Pb(Zn_1/2W_1/2)O₃–xPb(Zr_0.5Ti_0.5)O₃ system, with x = 0.80, 0.85, 0.90, and 0.95, were synthesized with the solid-state reaction technique. The perovskite phase formation in the sintered ceramics was analyzed with X-ray diffraction. It shows that the rhombohedral and the tetragonal phases coexist in the ceramic with x = 0.90, indicating the morphotropic phase boundary (MPB) within this pseudo-binary system. Dielectric and ferroelectric properties measurements indicate that the transition temperature decreases while the remanent polarization increases with the addition of Pb(Zn_1/2W_1/2)O₃. In the composition of x = 0.85 which is close to the MPB in the rhombohedral side, a high piezoelectric property with d ₃₃ = 222 pC/N was observed.     

Dielectric properties of Pb[(1?x)(Zr1/2Ti1/2)?x(Zn1/3Ta2/3)]O3 ceramics prepared by columbite and wolframite methods

Polycrystalline samples of Pb[(1 − x)(Zr_1/2Ti_1/2) − x(Zn_1/3Ta_2/3)]O ₃ , where x = 0.1–0.5 were prepared by the columbite and wolframite methods. The crystal structure, microstructure, and dielectric properties of the sintered ceramics were investigated as a function of composition via X-ray diffraction (XRD), scanning electron microscopy (SEM), and dielectric spectroscopy. The results indicated that the presence of Pb(Zn_1/3Ta_2/3)O₃ (PZnTa) in the solid solution decreased the structural stability of overall perovskite phase. A transition from tetragonal to pseudo-cubic symmetry was observed as the PZnTa content increased and a co-existence of tetragonal and pseudo-cubic phases was observed at a composition close to x = 0.1. Examination of the dielectric spectra indicated that PZT–PZnTa exhibited an extremely high relative permittivity at the MPB composition. The permittivity showed a ferroelectric to paraelectric phase transition at 330 °C with a maximum value of 19,600 at 100 Hz at the MPB composition.     

The effect of poling treatment and crystal structure of PZT on fracture toughness and fatigue resistance

Empirical measurements of fracture toughness and fatigue strength were conducted for piezoelectric Pb(Zr _x ,Ti_{1 – x} )O₃ of various compositions such as tetragonal, MPB, and rhombohedral. Before the poling treatment the rhombohedral showed the highest fracture toughness, while the tetragonal revealed the lowest fracture toughness. After poling treatment, the fracture toughness measured by the pre-cracked SENB method decreased in all three compositions. The most remarkable decrease was observed in the tetragonal composition. However, when the indentation strength method was used the highest fracture toughness was observed in the tetragonal. The stress intensity factor relief due to microcracks around the indentation marks and the anisotropic internal stresses caused by domain alignment during the poling treatment were proposed as explanations for the comflicting results. Fatigue resistance was lowered by the compressive stress introduced during the poling treatment. The highest fatigue resistance was observed in the rhombohedral composition of low tetragonality, which exhibited low internal stress.     

Structural studies of BiFeO3 modified BMZ-PT ceramics

Bismuth perovskites have been attracting attention as a family of piezoelectric ceramics in place of the widely used Pb (Zr, Ti)O₃ (PZT) system. The advantages of bismuth perovskites over PZT are environmentally more-friendly materials, a higher mechanical strength and Curie temperature. Most recently BiMgZrO₃-PbTiO₃ has been reported to be high temperature morphotropic phase boundary (MPB) piezoelectric with appreciably good ferroelectric and piezoelectric properties.Bismuth containing crystalline solutions [(BiMgZrO₃)_1−y-(BiFeO₃)_y]_x-(PbTiO₃)_1−x, (BMZ-BF-PT) have been synthesized by high temperature solid-state reaction technique. The crystalline symmetry varied with the composition, indicating good solid-state solubility of BMZ and BF with PT. X-ray diffraction (XRD) reveals that BMZ-BF-PT has a single-phase perovskite structure. The Morphotropic Phase Boundary (MPB) of BMZ-PT system lies in the region x = 0.55 to x = 0.6 which is supported by the transformation from tetragonal to rhombohedral phase. The SEM photographs reveal the uniform distribution of grains in the matrix. Variation of dielectric parameters with frequency (at room temperature) exhibit typical dielectric behavior for all compositions.     

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.     

Piezoelectric properties of [Bi<Subscript>0.5</Subscript>(Na<Subscript>0.7</Subscript>K<Subscript>0.25</Subscript>Li<Subscript>0.05</Subscript>)<Subscript>0.5</Subscript>]TiO<Subscript>3</Subscript>−Ba(Ti,Zr)O<Subscript>3</Subscript> binary system ceramics

Dense lead-free binary system piezoelectric ceramics (1 − x)[Bi_0.5(Na_0.7K_0.25Li_0.05)_0.5]TiO₃−xBa(Ti_0.95Zr_0.05)O₃ (BNKLT–BZT) were prepared by a two-step sintering process. A phase transition from rhombohedral to tetragonal was observed with increasing BZT fraction in the range x = 0.06–0.1 and the morphotropic phase boundary (MPB) between rhombohedral and tetragonal appears in this range. Ceramics containing 10 mol% BZT with tetragonal phase near the MPB region has the maximum piezoelectric constant d ₃₃(151pC/N).     

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.     

Morphotropic phase boundary and piezoelectric properties of (Bi1/2Na1/2)1 − x(Bi1/2K1/2)xTiO3-0.03(Na0.5K0.5)NbO3 ferroelectric ceramics

Lead-free piezoelectric ceramics, (Bi_1/2Na_1/2)_1 − x(Bi_1/2K_1/2)_xTiO₃-0.03(Na_0.5K_0.5)NbO₃ (x = 0.10-0.40) were synthesized by conventional solid-state sintering. A morphotropic phase boundary (MPB) between rhombohedral and tetragonal phases was confirmed. Two dielectric anomalies can be observed, showing diffused phase transition behavior. There is no shift of the dielectric maximum temperature with frequency due to the contribution of space charge at high temperatures, similar to pure (Bi_1/2Na_1/2)TiO₃. The materials near MPB show a strong compositional dependence with the optimal properties of a d₃₃ of 167 pC/N, a k_p of 35.5%, a P_r of 27.6 μC/cm² and a E_c of 27.9 kV/cm, suitable for future application.     

Structural investigations on Pb(ZrxT1?x)O3 solid solutions using the X-ray Rietveld method

Solid solutions in the series Pb(Zr _x Ti_1-x )O₃ which belong to ABO₃ type compounds were studied using the X-ray Rietveld technique from the tetragonal PbTiO₃ end to Pb(Zr_0.53 Ti_0.47)O₃ which is near the morphotropic phase boundary. A systematic structure analysis carried out for this series revealed that tetragonal and rhombohedral phases coexist even when Zr/Ti ratio is 40/60. Quantitative phase analysis using Rietveld method has been carried out for compositions falling in the two phase region. Substantial decrease in distortions of the BO₆ octahedra has been observed for the compositions near the morphotropic phase boundary.     

Piezoelectric properties,hysteresis behaviour and dielectric properties of PMN-PZT ceramics

Ferroelectric and piezoelectric properties ofxPb(Mg_1/3Nb_2/3)O₃−(1−x)Pb (Zr_0·55Ti_0·45)O₃ system have been investigated. X-ray diffraction patterns indicate rhombohedral and cubic structures. Maximum dielectric constant and piezoelectric properties are exhibited by 0·5–0·5 PMN-PZT composition.P _r is high in 0·6–0·4 PMN-PZT composition.     

Ferroelectricity of Pb(Zn1/3Nb2/3)O3-BaTiO3-PbTiO3 ceramics in the vicinity of morphotropic phase boundary

The morphotropic phase boundary (MPB) in the (0.85 – x)Pb(Zn_1/3Nb_2/3)O₃ – 0.15BaTiO₃ – xPbTiO₃(0 < x < 0.2) ceramic system was delineated by x-ray diffraction analysis. Polarization hysteresis loop measurements at room temperature were performed for compositions in the vicinity of the MPB. Experimental results demonstrate that the MPB, by its definition the rhombohedral and tetragonal phase coexist in the present system, is a broad composition region where the value of x ranges from 0.12 to 0.18. The remanent polarization, P _r, increases with PbTiO₃(PT) reaching a maximum value of 18 C/cm² at 15 mol%PT, then decreases remarkably with further PT addition, whereas the variation of coercive field, E _c, with PT content shows the opposite trend. The effect of PT incorporation on P _r is more pronounced than on E _c. Correlation between the degree of lattice distortion, instead of the maximization of the polarization orientations inherent to both phases, and P _r is attained to account for the observed phenomenon. The dependence of E _c upon PT content, however, reflects the transition from typical relaxor ferroelectrics to weak normal ferroelectrics, as confirmed by the results of the dielectric measurement.     

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.