Inverse hysteresis of field induced elastic deformation in the solid solution 90 mol% Pb(Mg1/3Nb2/3)O3-10 mol% PbTiO3

Elastic deformations induced by high electric fields in the solid solution system Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ have been measured using a strain gauge method at temperatures in the relaxation range. Unusual inverse hysteretic curves have been observed in the relation between the deformation and electric field typically in 90 mol% Pb-(Mg_1/3Nb_2/3)O₃-10 mol% PbTiO₃ at temperatures outside the range where they would be of practical use in electrostrictive displacement control.     

Synthesis of a solid solution of PbTiO3-PbZrO3-Pb (Mg1/3Nb2/3)O3 system through use of 8-quinolinol and its properties

A new method for the synthesis of a solid solution of PbTiO₃-PbZrO₃-Pb (Mg_1/3Nb_2/3)O₃ system (PZTMN) has been developed. An aqueous solution of Ti⁴⁺, Zr⁴⁺, Mg²⁺ and Nb⁵⁺ was dropped into a solution of 8-quinolinol in aqueous ammonia. The precipitate formed was washed, dried and fired, then an oxide (ZTMN) was obtained. The best firing temperature for the precipitate was 700 °C. The ZTMN powder was then mixed with PbO powder: when this mixture was fired, PZTMN was formed directly. By a conventional solid-state reaction among PbO, ZrO₂, TiO₂, MgO and Nb₂O₅ ([P + Z + T + M + N] method), PbTiO₃ and Pb(Mg_1/3Nb_2/3)O₃ were formed as intermediate products during the reaction. The single phase of PZTMN was obtained at 1200 °C for the [P + Z + T + M + N] method and at 800 °C for the new [P + ZTMN] method. The compositional fluctuation of PZTMN prepared by the [P + ZTMN] method was very small, and its dielectric constant was much higher than that of PZTMN prepared by the [P + Z + T + M + N] method. The density of PZTMN prepared by the [P + ZTMN] method practically attained the theoretical density under conditions of calcining at 800 °C and sintering at 1100 °C for 1 h.     

Synthesis and characterization of pseudo-ternary Pb(Fe<Subscript>1/2</Subscript>Nb<Subscript>1/2</Subscript>)O<Subscript>3</Subscript>-PbZrO<Subscript>3</Subscript>-PbTiO<Subscript>3</Subscript> ferroelectric ceramics via a B-site oxide mixing route

Perovskite phase formation and dielectric/ferroelectric properties of the pseudo-ternary Pb(Fe_1/2Nb_1/2)O₃-PbZrO₃-PbTiO₃ (PFN-PZ-PT) ferroelectric ceramics have been investigated as promising materials for multi-layer ceramic capacitors. Complete solid solution with pure perovskite phase can be formed in this system in the whole composition range studied using conventional solid-state reaction method via a B-site oxide mixing route. Crystal lattice of the ceramics obtained shrinkages with the increase of the concentration of Pb(Fe_1/2Nb_1/2)O₃ (PFN) and expands with the increase of the content of PbZrO₃ (PZ). With the increase of the concentration of PbTiO₃ (PT), crystal structure of PFN-PZ-PT changes from pseudo-cubic ferroelectric phase to tetragonal one while retains the fraction of PFN as constant. A morphotropic phase boundary (MPB) forms at the composition of 42 mol% PT regardless of whatever concentration of PFN, and the content of PFN affects little on the composition of MPB. The preliminary phase diagram of the PFN-PZ-PT system is determined by X-ray diffraction (XRD) measurements combining with dielectric/ferroelectric characterization. Dielectric measurements indicate that the value of dielectric maximum (ɛ_m) and the temperature where ɛ_m appears (T_m) increase with the increase of the concentration of PT. However, PFN exhibits opposite effects, i.e., ɛ_m increases with the increase of the concentration of PFN accompanied by the decrease of T_m.     

Perovskite phase formation in the PbMg1/3Nb2/3 O3-PbZrO3-PbTiO3 system by the columbite route

The reaction mechanism of PbMg_1/3Nb_2/3O₃-PbZrO₃-PbTiO₃ (PMN-PZT) perovskite phase prepared by the columbite route has been studied in the temperature range from 600 to 800 °C. The effects of heating and cooling rate during the calcination of 3PbO +MgNb₂O₆+PZT powder mixtures have also been investigated. Nearly pure perovskite phase, 0.9 PMN-0.1 PZTsolid solution with no pyrochlore phase, as determined by X-ray diffraction, could be prepared at 800 °C for 2 H. From DTA/TGA, dilatometry and XRD data the reaction mechanism of PMN-PZT solid solution formation could be divided into three steps: (i) decomposition of columbite (MgNb₂O₆) by reacting with PbO at 350 to 600 °C (ii) the formation of a B-site-deficient pyrochlore phase Pb₂Nb_1.33Mg_0.17O_5.50 at close to 650 °C, and (iii) the formation of perovskite phase PMN-PZT solid solution from the reaction of Pb₂Nb_1.33Mg_0.17O_5.50 pyrochlore phase with MgO and PZT above 650 °C.     

Electric-field-induced strain and piezoelectric properties of a high Curie temperature Pb(In1/2Nb1/2)O3-PbTiO3 single crystal

The temperature dependence of dielectric and piezoelectric properties, electric-field-induced strains of 0.66 Pb(In_1/2Nb_1/2)O₃-0.34 PbTiO₃ single crystals, which were grown directly from melt by using the modified Bridgman technique with the allomeric Pb(Mg_2/3Nb_1/3)O₃-PbTiO₃ seed crystals, were determined as a function of crystallographic orientation with respect to the prototypic (cubic) axes. Ultrahigh piezoelectric response (d₃₃∼2000 pC/N, k₃₃∼94%) and strain levels up to 0.8%, comparable to rhombohedral (1−x)Pb(Mg_2/3Nb_1/3)O₃-xPbTiO₃ and (1−x)Pb(Zn_2/3Nb_1/3)O₃-xPbTiO₃ single crystals, were observed for the 〈0 0 1〉-oriented crystals. Strain levels up to 0.47% and piezoelectric constant d₃₃∼1600 pC/N could be achieved being related to an electric-field-induced rhombohedral-orthorhombic phase transition for the 〈1 1 0〉-oriented crystals. In addition, high electromechanical coefficients k₃₃ (∼88%) can be achieved even heating to 110 °C. High T_C (∼200 °C), large electromechanical coefficients k₃₃ (∼94%) and low dielectric loss factor (∼1%), along with large strain make the crystals promising candidates for a wide range of electromechanical transducers.     

Effects of Fe2O3 doping on the microstructure and piezoelectric properties of 0.55Pb(Ni1/3Nb2/3)O3-0.45Pb(Zr0.3Ti0.7)O3 ceramics

0.55Pb(Ni_1/3Nb_2/3)O₃-0.45Pb(Zr_0.3Ti_0.7)O₃(PNN-PZT) ceramics with different concentration of xFe₂O₃ doping (where x = 0.0, 0.8, 1.2, 1.6 mol%) were synthesized by the conventional solid state sintering technique. X-ray diffraction analysis reveals that all specimens are a pure perovskite phase without pyrochlore phase. The density and grain size of Fe-doped ceramics tend to increase slightly with increasing concentration of Fe₂O₃. Comparing with the undoped ceramics, the piezoelectric, ferroelectric and dielectric properties of the Fe-doped PNN-PZT specimens are significantly improved. Properties of the piezoelectric constant as high as d₃₃ ~ 956 pC/N, the electromechanical coupling factor k_p ~ 0.74, and the dielectric constant ε_r ~ 6095 are achieved for the specimen with 1.2 mol% Fe₂O₃ doping sintered at 1200 °C for 2 h.     

Properties of multilayer composite thin films based on morphotropic phase boundary Pb(Mg1/3Nb2/3)O3-PbTiO3

It has been reported that ferroelectric and piezoelectric properties of Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (PMNT) thin films, with compositions close to the morphotropic phase boundary (MPB), show lower values than those reported for bulk ceramics with the same composition, which has been attributed to a reduction of the remnant polarization caused by the small size of the grains in the films. An alternative has been proposed to take full advantage of the excellent piezoelectric properties of polycrystalline PMNT in thin film form: a multilayer configuration that uses ferroelectric layers with large remnant polarization, in this case PbTiO₃, to generate an internal electric bias within the PMNT layers and, thus, anchor an induced polarization on them, resulting in a consequent large piezoelectric behavior. The detailed study of the properties of these multilayer composite films reveals the complex correlations that arise in these heterostructures, which are key for the design of optimized piezoelectric films based on MPB PMNT.     

The Influence of Interface Reactions Between Ceramics and Electrodes on Ceramic Properties

In a multilayered ceramic actuator structure, controlling the interface between the electrode and the ceramics is an essential technology for obtaining highly reliable ceramic actuators. The interface between Ag-Pd internal electrode and Pb(Ni_1/3Nb_2/3)O₃-PbTiO₃-PbZrO₃(PNN-PT-PZ), and the grain boundary in PNN-PT-PZ ceramics, were studied using TEM and EDS. We found that Pb diffuses into the Ag-Pd electrode during firing. At the initial sintering stage, Ag in Ag-Pd seems to diffuse into the piezoelectric ceramics along the grain boundary. Ag diffused in the grain boundary is segregated, and a small amount of Ag diffuses into the grain of the ceramics at the medium sintering stage. When compared to the thick film process, the interfacial reaction between Ag-Pd and PNN-PT-PZ is promoted more in the cofiring process than the thick film process. This is because more Pb vapors diffuse into Ag-Pd in the cofiring process than the thick film process. The addition of Ag into PNN-PT-PZ decreases the dielectric constant and affects the dielectric loss slightly.     

Perovskite phase formation and microstructural evolution of lead magnesium tungstate-lead titanate ceramics

The perovskite phase formation and microstructural evolution in the Pb(Mg_0.5W_0.5)O₃-PbTiO₃ system have been investigated in this work. During the solid-state reaction of Pb(Mg_0.5W_0.5)O₃, only PbWO₄ and Pb₂WO₅ are formed as intermediate phases at low temperature range. Moreover, the perovskite phase Pb(Mg_0.5W_0.5O₃ begins to form at 600 °C and is complete at 850 °C. As Pb(Mg_0.5W_0.5)O₃ is doped with PbTiO₃, the formation of the perovskite phase becomes sluggish and the temperature for the complete reaction to take place increases up to 1000 °C. The doping of the Pb(Mg_0.5W_0.5)O₃ with PbTiO₃ apparently induces the formation of a small amount of liquid phase, which is possibly attributed to a reaction with residual Pb₂WO₅. This liquid phase not only accelerates the densification of specimens through a liquid phase sintering mechanism, but also causes abnormal grain growth, thereby forming an inhomogeneous microstructure. The dielectric permittivity of Pb(Mg_0.5W_0.5)O₃ does not depend on frequency, and a sharp phase transformation from the antiferroelectric to the paraelectric state occurs at around 40 °C. In contrast, the dielectric properties and broad phase transformation temperatures of Pb(Mg_0.5W_0.5)_0.9Ti_0.1O₃ and Pb(Mg_0.5W_0.5)_0.6Ti_0.4O₃ strongly depend on frequency. This dependency would imply that the PbTiO₃ addition to Pb(Mg_0.5W_0.5)O₃ alters the order arrangement of B-site cations to a disordered state and induces relaxor-ferroelectric characteristics.     

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).     

Electrical properties of Pb(Mg1/3Nb2/3)O3-PbTiO3 ceramics modified with WO3

Ferroelectrics 0.67Pb (Mg_1/3Nb_2/3)O₃-0.33PbTiO₃ (PMN-PT) + x mol% WO₃ (x=0.1, 0.5, 1, 2) were prepared by columbite precursor method. Electrical properties of WO₃-modified ferroelectrics were investigated. X-ray diffraction (XRD) was used to identify crystal structure, and pyrochlore phase were observed in 0.67Pb (Mg_1/3Nb_2/3)O₃-0.33PbTiO₃+2 mol% WO₃. Dielectric peak temperature decreased with WO₃ doping, indicating that W⁶⁺ incorporated into PMN-PT lattice. Lattice constant, pyrochlore phase and grain size contribute to the variation of K_max. Both piezoelectric constant (d₃₃) and electromechanical coupling factors (k_p) were enhanced by doping 0.1 mol% WO₃, which results from the introduction of “soft” characteristics into PMN-PT, while further WO₃ addition was detrimental. We consider that the two factors, introduction of “soft” characteristics and the formation of pyrochlore phase, appear to act together to cause the variation of piezoelectric properties of 0.67PMN-0.33PT ceramics doping with WO₃.     

Growth and electrical performance of Pb(Mg1/3Nb2/3)O3-PbTiO3-Pb(Fe1/2Nb1/2)O3 single crystals

For the first time, we have grown ferroelectric single crystals Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃-Pb(Fe_1/2Nb_1/2)O₃ (PMN-PT-PFN) from the melt by the simple slow cooling process. The chemical composition of the single crystals PMN-PT-PFN (0.59/0.31/0.10) is near the morphotropic phase boundary (MPB). X-ray diffraction (XRD) was used to study phase structure of the as-grown crystals, energy dispersive X-ray spectrometer (EDS) and electron probe micro-analyzer (EPMA) were employed to confirm the chemical composition and element distribution of the as-grown crystals, respectively. The ferroelectric, dielectric and piezoelectric properties of the as-grown PMN-PT-PFN (0.59/0.31/0.10) single crystal oriented along the (0 0 1) axis were measured, which showed that the remnant polarization (P_r), coercive electric fields (E_c), the Curie temperature (T_c) and the piezoelectric coefficient (d₃₃) were 50.2 μC/cm², 13.9 kV/cm, 158 °C and about 1800 pC/N, respectively. All the results indicated that the PMN-PT-PFN (0.59/0.31/0.10) single crystals are promising for applying to field of high frequency.     

Structure and ferroelectric properties in (K0.5Bi0.5)TiO3-BiScO3-PbTiO3 piezoelectric ceramic system

(K_0.5Bi_0.5)TiO₃-BiScO₃-PbTiO₃ ceramics were synthesized by conventional solid-state method. A morphotropic phase boundary (MPB) was confirmed with the aid of structural analysis. Two dielectric anomalous peaks were observed, the one around dielectric maximum temperature (T_m) due to phase transformation from ferroelectric to paraelectric while the second one could be ascribed to space charges. Furthermore, the existence of space charges also resulted in the independence of T_m with frequency at low lead composition. A new high temperature piezoelectric ceramic, 0.30(K_0.5Bi_0.5)TiO₃-0.30BiScO₃-0.40PbTiO₃ close to MPB exhibited excellent electrical properties with T_m of 384 °C, d₃₃ of 247 pC/N, k_p of 38.9%, P_r of 19.41 μC/cm², and E_c of 2.25 kV/mm, indicative of a candidate for high temperature application.     

Effect of CeO<Subscript>2</Subscript> on dielectric,ferroelectric and piezoelectric properties of PMN–PT (67/33) compositions

Lead magnesium niobate–lead titanate [Pb(Mg_1/3Nb_2/3)O₃–PbTiO₃] powders doped with different mole % of CeO₂ were prepared by a modified columbite route with compositions corresponding to morphotropic phase boundary (MPB) region. These powders were calcined at 800 °C for 4 h and circular test specimens were prepared by uniaxial pressing. The specimens were sintered at 1150 °C/2 h, poled at 2 kV/mm d.c. voltage and were characterized for dielectric, ferroelectric and piezoelectric properties. It was observed that the piezoelectric and ferroelectric properties initially increase up to 2 mol% of ceria addition and then decrease with increase in ceria concentration. The diffusivity of the dielectric curves increases with increase in ceria concentration. The decrease in Curie temperature was observed from 173 °C corresponding to pure PMN–PT to a temperature of 138 °C for 10 mol% of ceria addition.     

Piezoelectric shear-mode properties of Pb(Yb1/2Nb1/2)O3-PbTiO3 ceramics

A Pb(Yb_1/2Nb_1/2)O₃-PbTiO₃ [PYNT] solid solution was synthesized and characterized for its potential use. The shear-mode dielectric and piezoelectric behaviors of PYNT with a morphotropic phase boundary (MPB) composition were studied as a function of temperature. Dielectric permittivity K₁₁^T and loss were found to be 2310 and 2.5%, respectively, at room temperature. Piezoelectric coefficient d₁₅ and electromechanical coupling factor k₁₅ were calculated to be 710 pC/N and 0.70, respectively, maintaining nearly constant up to 300 °C, resistivity and RC time constant were observed to be 2.4 × 10⁹ Ω cm and 1.07 s, respectively, at 350 °C. These good piezoelectric properties, together with the high Curie temperature (T_c ∼ 370 °C), indicate that PYNT is a promising candidate for high temperature-shear sensor and inkjet actuator applications.     

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.     

Triple-like hysteresis loop and microdomain-macrodomain transformation in the relaxor-based 0.76Pb(Mg1/3Nb2/3)O3-0.24PbTiO3 single crystal

Polarization and depolarization behavior of the relaxor-based 0.76Pb(Mg_1/3Nb_2/3)O₃-0.24PbTiO₃ single crystal has been studied between 25 and 200 °C by means of dielectric measurement with or without dc bias, Polarization-Electric field (P-E) hysteresis loop and discharging current measurements. Triple-like P-E loops were obtained in a temperature range between 80 and 90 °C, disclosing the transformation between microdomain state and metastable macrodomain state. For the poled crystals, the microdomain state with dipoles partially oriented was indicated to exist in the similar temperature range and mediate between the lower temperature macrodomain state with dipoles oriented and the higher temperature microdomain state with dipoles in a random system.     

Structure and physical properties of tetragonal PbMg<Subscript>1/3</Subscript>Nb<Subscript>2/3</Subscript>O<Subscript>3</Subscript>-PbTiO<Subscript>3</Subscript> solid solutions

The principal bond distances in the structure of tetragonal PbMg_1/3Nb_2/3O₃-PbTiO₃ (PMN-PT) solid solutions have been determined by the Rietveld method. The ferroelectric state of (PbMg_1/3Nb_2/3O₃)_0.62(PbTiO₃)_0.38 samples is shown to be governed by the displacement of the Pb ions from their ideal crystallographic site. In the frequency range 4000–5000 cm^?1, the refractive index of the samples is 2.70–2.75, as determined by the Kramers-Kronig method.     

Piezoelectric anisotropy: Enhanced piezoelectric response along nonpolar directions in perovskite crystals

This paper discusses the mechanisms that can contribute to the enhanced longitudinal piezoelectric effect along nonpolar directions in perovskite crystals, such as BaTiO₃, PbTiO₃, KNbO₃, Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ and Pb(Zn_1/2Nb_2/3)O₃-PbTiO₃. Piezoelectric anisotropy is discussed in relation to temperature induced phase transitions, compositional variation in solid solutions with morphotropic phase boundaries, applied electric fields, the domain wall structure and domain wall displacement.     

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.