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.     

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.     

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.     

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.     

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.     

Synthesis and characterization of 0.65Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 fibers with Pt core

This paper reports the synthesis and electromechanical characterization of 0.65Pb(Mg_1/3Nb_2/3)O₃-0.35PbTiO₃ (PMN-35PT) ceramics and fibers. To prevent the lead loss during the sintering of the fibers, lead-atmosphere was used during the sintering process. As a consequence, it was possible to ensure a good densification of the fiber and a pure perovskite phase. The electromechanical coupling factor and piezoelectric coefficient of the piezoelectric fiber were found to be k₃₁ = 0.20 and d₃₁ = −130 pC/N, respectively. These results are lower than ceramic sample properties (k₃₁ = 0.32 and d₃₁ = −234 pC/N). In order to determine reasons for these lower results in fiber shape sample, density and poling studies were performed. It is shown that fiber shape samples cannot be poled correctly because of the ratio between core and ceramic diameters.     

Stoichiometric Pb(Mg1/3Nb2/3)O3 perovskite ceramics produced by reaction-sintering process

Stoichiometric lead magnesium niobate, Pb(Mg_1/3Nb_2/3)O₃ (PMN), perovskite ceramics produced by reaction-sintering process were investigated. Without calcination, a mixture of PbO, Nb₂O₅, and Mg(NO₃)₂ was pressed and sintered directly. Stoichiometric PMN ceramics of 100% perovskite phase were obtained for 1, 2, and 4 h sintering at 1250 and 1270 °C. PMN ceramics with density 8.09 g/cm³ (99.5% of theoretical density 8.13 g/cm³) and K_max 19,900 under 1 kHz were obtained.     

Composition dependent phase connectivity, dielectric and magnetoelectric properties of magnetoelectric composites with Pb(Mg1/3Nb2/3)0.67Ti0.33O3 as piezoelectric phase

Ferrite (Ni_0.6Co_0.4Fe₂O₄) phase, ferroelectric (Pb(Mg_1/3Nb_2/3)_0.67Ti_0.33O₃) phase and magnetoelectric composites of (x)Ni_0.6Co_0.4Fe₂O₄ + (1 − x)Pb(Mg_1/3Nb_2/3)_0.67Ti_0.33O₃ with x = 0.15, 0.30 and 0.45 were prepared using solid-state reaction technique. Presence of Ni_0.6Co_0.4Fe₂O₄ and Pb(Mg_1/3Nb_2/3)_0.67Ti_0.33O₃ was confirmed using X-ray diffraction technique. The scanning electron microscopic images were used to study the microstructure of the composites. Connectivity scheme present in the magnetoelectric (ME) composites are discussed from the microscopic images. Variation of dielectric constant and dielectric loss with temperature for all the composites was studied. Here we report the effect of Ni_0.6Co_0.4Fe₂O₄ mole fraction on connectivity schemes between Ni_0.6Co_0.4Fe₂O₄ and Pb(Mg_1/3Nb_2/3)_0.67Ti_0.33O₃ composite. The variation of magnetoelectric voltage coefficient with dc magnetic field shows peak behaviour. The maximum value of magnetoelectric voltage coefficient of 9.47 mV/cm Oe was obtained for 0.15Ni_0.6Co_0.4Fe₂O₄ + 0.85Pb(Mg_1/3Nb_2/3)_0.67Ti_0.33O₃ composites. Finally we have co-related the effect of Ni_0.6Co_0.4Fe₂O₄ content and dielectric properties on magnetoelectric voltage coefficient.     

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.     

Effect of MnO2 addition on the piezoelectric properties in Pb(Mg1/3Nb2/3)O3 relaxor ferroelectrics

The effects of MnO₂ addition on the piezoelectric properties in Pb(Mg_1/3Nb_2/3)O₃ relaxor ferroelectrics were studied in the ferroelectricity-dominated temperature range from −40 to 30°C. Dielectric, piezoelectric, and electrostrictive properties were examined to clarify the effect of MnO₂ addition. As an added amount of MnO₂ increases, the dielectric constant decreases and the mechanical quality factor increases in Pb(Mg_1/3Nb_2/3)O₃. From the experimental results, it has been found that Mn behaves as a ferroelectric domain pinning element.     

Distribution of pyrochlore phase in Pb(Mg1/3Nb2/3)O3-PbTiO3 films and suppression with a Pb(Zr0.52Ti0.48)O3 interfacial layer

Thin films of the relaxor ferroelectric Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (PMN-PT) on Pt/Ti/SiO₂/Si (Pt/Si) substrates both with and without a Pb(Zr_0.52Ti_0.48)O₃ (PZT) interfacial layer were investigated. Perovskite and pyrochlore coexistence was observed for PMN-PT thin films without a PZT interfacial layer. Interestingly, most of the pyrochlore phase was observed in single-coated films and in the first layer of multi-coated films. The pyrochlore phase exhibited grains with an average size of about 25 nm, which is smaller than those of the perovskite phase (about 90 nm). In contrast, for PMN-PT thin films grown on a PZT interfacial layer, the formation of a pyrochlore phase at the interface between PMN-PT layers and the substrate is completely suppressed. Moreover, small grains are not observed in the films with a PZT interfacial layer. The measured polarization-electric field (P-E) hysteresis loops of PMN-PT films with and without PZT layers indicate that enhanced electrical properties can be obtained when a PZT interfacial layer is used. These enhanced properties include an increase in the value of remanent polarization P_r from 2.7 to 5.8 μC/cm² and a decrease in the coercive field E_c from 60.5 to 28.0 kV/cm.     

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.     

Effect of Pb(Zn1 / 2W1 / 2)O3 introduction on perovskite development and dielectric properties of (Ba,Pb)TiO3

Powders of a Pb(Zn_1 / 2W_1 / 2)O₃-introduced BaTiO₃-PbTiO₃ system were prepared. A two-step calcination route of a B-site precursor method was employed to promote perovskite formation. The overall effects of the Pb(Zn_1 / 2W_1 / 2)O₃ incorporation on changes in crystalline aspects as well as dielectric properties were explored.     

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.     

Neutron powder diffraction and magnetic study of perovskites Pb(Mn1/2Nb1/2)O3 and Pb(Mn1/4Fe1/4Nb1/2)O3

The structural and magnetic properties of the complex metal oxides Pb(Mn_1/2Nb_1/2)O₃ (PMNO) and Pb(Mn_1/4Fe_1/4Nb_1/2)O₃ (PMFNO), which belong to a class of disordered perovskites have been studied. The magnetic susceptibilities of PMNO showed hysteresis between field cooled and zero-field cooled conditions below the transition of 15 K, suggesting that the material has a spin-glass feature. Neutron diffraction patterns of PMNO showed no evidence of a long-range magnetic ordering at 1.5 K, which is consistent with spin-glass behavior. Rietveld refinements of neutron powder diffraction data collected at different temperatures between 1.5 and 700 K have been carried out in order to extract structural information. The crystal structure of this compound is cubic (space group Pmm) within the whole temperature interval. The Mn and Nb ions were found to be disordered over the perovskite B-sites. The main feature of this structure is the positional disorder at the Pb site, the importance of which in connection with the ferroic transitions is briefly discussed. The Pb cations show a positional disorder shifting from their high-symmetry positions along the [1 1 1] direction. The effect of Fe-doping on PMNO has been studied. The substitution of Fe at the Mn site in PMFNO results in a small changes of the magnetic properties without significant differences in the crystal structures. The factors governing the observed structural and magnetic properties of PMNO and PMFNO are discussed and compared with those of other quaternary Mn-containing perovskites. For the PbB³⁺_1/2Nb_1/2O₃ series with the isomorphous substitution B³⁺, graphs of average lattice parameters of the perovskite phase and the temperatures of ferroelectric and magnetic phase transitions as functions of the B³⁺ cation radius were constructed and are discussed. Influence of A-cation sublattice on magnetic properties is also considered.     

Dielectric properties of a new ceramic system (1 − x)Mg4Nb2O9-xCaTiO3 at microwave frequency

The microstructures and the microwave dielectric properties of the (1 − x)Mg₄Nb₂O₉-xCaTiO₃ ceramic system were investigated. In order to achieve a temperature-stable material, CaTiO₃ (τ_f ∼ 800 ppm/°C) was chosen as a τ_f compensator and added to Mg₄Nb₂O₉ (τ_f ∼ −70 ppm/°C) to form a two phase system. It was confirmed by the XRD and EDX analysis. By appropriately adjusting the x-value in the (1 − x)Mg₄Nb₂O₉-xCaTiO₃ ceramic system, near-zero τ_f value can be achieved. A new microwave dielectric material, 0.5Mg₄Nb₂O₉-0.5CaTiO₃ applicable in microwave devices is suggested and possesses the dielectric properties of a dielectric constant ?_r ∼ 24.8, a Q × f value ∼82,000 GHz (measured at 9.1 GHz) and a τ_f value ∼−0.3 ppm/°C.     

The influence of defects on ferroelectric and pyroelectric properties of Pb(Mg1/3Nb2/3)O3-0.28PbTiO3 single crystals

Relaxor-based ferroelectric single crystals 0.72Pb(Mg_1/3Nb_2/3)O₃-0.28PbTiO₃ (PMN-0.28PT) were grown by a modified Bridgman technique. The direct current (dc) conductivity was investigated and corresponding conduction mechanisms were discussed. V^″Pb−VO defects are dominant from 245 °C to 650 °C. The ferroelectric properties of [1 1 1]-oriented PMN-0.28PT were systematically investigated, with the coercive field (E_c) of 5.2 kV cm⁻¹ and remnant polarization (P_r) of 37.8 μC cm⁻² at room temperature. Moreover, the dielectric and pyroelectric performances of PMN-0.28PT were measured and the integrated pyroelectric performances greatly enhanced after annealing in oxygen at 500 °C for 20 h. This is due to the decrease of oxygen vacancies in the single crystals when being annealed in the oxygen-rich atmosphere. These make [1 1 1]-oriented PMN-0.28PT crystals a promising candidate for infrared detectors and thermal imagers used at room temperature.     

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.     

Crystallographic and dielectric properties of barium-substituted Pb(Mg1/3Ta2/3)O3 ceramics

Ceramic powders of (Ba,Pb)Pb(Mg_1/3Ta_2/3)O₃ were prepared via a B-site precursor route. Crystal symmetries and lattice parameters were determined. Monophasic perovskite was developed after the two-step reaction process, in which the lattice parameters showed linear changes in the entire composition range. Dielectric responses of the ceramics with compositional and frequency changes were investigated. The results were also compared with the (Ba,Pb)(Zn_1/3Ta_2/3)O₃ data.