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.     

Structural study of Pb(Mg1/3Nb2/3)O3 at low temperatures

The structure of the relaxor ferroelectric Pb(Mg_1/3Nb_2/3)O₃ crystal was studied with the X-ray single crystal diffraction at 110, 224 and 293 K. The remarkable redistribution of the reflections intensities at low temperatures was observed. The structure of the low temperature phase is described with the model of the substantially nonuniform displacements of the lead ions using the derived analytical expression of the scattering form-factor. The structure refinement shows the good agreement between the model and the experimental data at low temperatures.     

Large electric field induced strain of Bi(Mg1/2Ti1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 ceramics textured by Template Grain Growth

<001> oriented xBi(Mg_1/2Ti_1/2)O₃-(0.7-x)Pb(Mg_1/3Nb_2/3)O₃-0.3PbTiO₃ (BMT-PMN-PT) textured ceramics are successfully fabricated by the template grain growth method using BaTiO₃ platelets as template. BMT-PMN-PT textured ceramics with different BMT contents are studied in terms of crystal structure, microstructures, dielectric and ferroelectric properties, and electric field induced strain. The as-fabricated BMT-PMN-PT textured ceramics were found to have a strong orientation along <001> direction. The frequency dispersion of dielectric constant of BMT-PMN-PT textured ceramics increases gradually and its relaxability becomes stronger with increasing BMT content. A large electric-field induced strain (0.42 % at 4 kV/mm) is obtained in 0.25BMT-0.45PMN-0.3PT textured ceramics with Lotgering factor 0.94, which is about 83 % enhancement than that of the randomly oriented ceramics (0.23 % at 4 kV/mm). The strain of 0.25BMT-0.45PMN-0.3PT textured ceramics have a relatively high thermal stability, with a slight decrease from 0.42 % to 0.28 % in the temperature range of 20−100 °C. Our research suggests that 0.25BMT-0.45PMN-0.3PT textured ceramics have a greatly potential for actuator devices applications owing to its advantages of large electric field induced strain response.     

Sm掺杂Pb(Mg1/3Nb2/3)O3-PZT压电陶瓷的研究

本文通过一步反应合成法制备了铌镁-锆钛酸铅(Pb(Mg_1/3Nb_2/3)O₃-Pb(Zr,Ti)O₃,PMN-PZT)压电陶瓷,研究了稀土元素钐(Sm)掺杂对PMN-PZT(x%(摩尔分数)Sm-PMN-PZT)结构与电学性能的影响规律,得到了具有高压电性、高机电耦合系数和高居里温度的压电陶瓷。当x=2.0时,压电常数d₃₃=611 pC/N,机电耦合系数k_p=0.68,介电损耗tan δ=1.65%,相对介电常数ε_r=2 650,居里温度T_C=283 ℃。测试压电陶瓷电致应变性能,在3 kV/mm下单极电致应变达到0.20%,显示出其大应变材料的特征。结果表明,Sm掺杂PMN-PZT压电陶瓷具有优异的综合电学性能,有望在换能器、传感器以及致动器等领域广泛应用。     

Fabrication of 0.24Pb(In1/2Nb1/2)O3-0.42Pb(Mg1/3Nb2/3)O3-0.34PbTiO3 transparent ceramics by conventional sintering technique

0.24Pb(In_1/2Nb_1/2)O₃-0.42Pb(Mg_1/3Nb_2/3)O₃-0.34PbTiO₃ transparent ceramics were fabricated by a conventional sintering technique. Through optimization of sintering conditions of calcination and sintering temperatures and time, the obtained ceramics showed high optical transmittance of 53% and 71% at light wavelengths of 1300 and 2000 nm, respectively. The ceramics showed a rhombohedral to tetragonal phase transition at ~120°C and a tetragonal to cubic phase transition at 222°C. These transition temperatures were higher than those of 0.67Pb(Mg_1/3Nb_2/3)-0.33PbTiO₃ ceramics. In addition, the ceramics had a ferroelectric hysteresis loop, a large piezoelectric constant d₃₃ of 407 pC/N, and a planar electromechanical coupling factor k_p of 52%. These results suggest that the transparent ceramics may be used as a temperature-stable, linear electro-optic material.     

Preparation of the Pb(Mg1/3Nb2/3)O3 films by aqueous tape casting

Lead magnesium niobate (PMN) is a relaxor ferroelectric material. Because of its high dielectric constant and superior electrostrictive properties it is commonly used in the manufacture of multilayer electronic devices which is typically produced by tape casting. However, preparation of PMN slurry formulations to use in aqueous tape casting process is not investigated in detail yet. Therefore, in this study aqueous PMN formulations were developed for tape casting and its relation with the final properties of PMN films were investigated. The slurries were prepared using poly(acrylic acid)-based comb polymer as the dispersant, nonionic acrylic latex as the binder and the hydroxypropyl methyl cellulose as the wetting agent. The results showed that it is possible to prepare flexible, crack-free PMN films using highly concentrated suspensions without using any plasticizer. The study gives guidelines for the aqueous tape casting of PMN and can be adapted to processing of other multi-component metal oxides.     

Fatigue-less electrocaloric effect in relaxor Pb(Mg1/3Nb2/3)O3 multilayer elements

A study was made of the electrocaloric (EC) effect’s stability in relaxor Pb(Mg_1/3Nb_2/3)O₃ multilayer elements. The sample was subjected to 10⁶ unipolar cycles at an electric field amplitude of 110 kV cm⁻¹. The dielectric and ferroelectric properties of the material change only slightly, while the microstructure does not reveal any detrimental evidence of the cycling. The initially measured EC temperature change of 1.45 K decreases by only 0.01 K upon cycling, exhibiting a fatigue-less behavior. The results justify the choice of relaxor multilayers as the working bodies in EC cooling devices, where the material should withstand numerous electric field cycles with high amplitudes, sometimes exceeding 100 kV cm⁻¹.     

The influence of oxygen vacancies on piezoelectricity in samarium-doped Pb(Mg1/3Nb2/3)O3-PbTiO3 ceramics

A study of 0.71Pb(Mg_1/3Nb_2/3)O₃-0.29PbTiO₃ shows that, when it is doped with 2.5% Sm on the A-site, in addition to an almost threefold increase in piezoelectric charge coefficient and dielectric permittivity, there is a 2 order of magnitude reduction in conductivity, attributed to a decrease in oxygen vacancy concentration. An analysis of the nonlinearity of permittivity with respect to field amplitude shows that both the reversible and irreversible contributions increase significantly with Sm-doping, with simple models showing that these changes are consistent with a reduction in the concentration of dipolar defects that can inhibit both polarization rotation and domain wall translation. Contrary to the argument that doping increases heterogeneity, there is little change in the diffuseness of the peak in permittivity as a function temperature, whilst there is a 15% increase in spontaneous polarization with Sm addition. Through comparison of the Rayleigh law parameters with those published for other piezoelectric materials, it is concluded that a significant contribution to the observed increase in piezoelectric performance due to Sm-doping of PMN-PT is similar in origin to that seen in soft, donor-doped PZT and other conventional piezoelectric ceramics.     

Tunability properties in the paraelectric state of the Pb(Mg1/3Nb2/3)O3 ceramics

Pb(Mg_1/3Nb_2/3)O₃ ceramics prepared via columbite method exhibit high crystallinity and high density after sintering at 1200 °C. Typical relaxor behavior are demonstrated by the dielectric data. Although showing a diffuse phase transition, at room temperature the system is in its paraelectric state, i.e. the PMN structure is fully cubic. The dc-tunability was investigated above the room temperature, when other field-induced contributions than ferroelectric polarization might cause non-linearity. A random non-interacting dipolar unit in a double well potential was employed to describe the ?(E) non-linearity. The temperature-dependence of the average polarization corresponding to the polar nanoregions in the paraelectric state of the PMN relaxor was calculated from the ?(E) data at various temperatures above T_m. A similar trend of decreasing as increasing temperature shows the spin-glass local order parameter determined from the dielectric constant data in the paraelectric state. The local order parameter in the paraelectric state is determined by the nanopolar domains size and correlations.     

Composition dependent structure,dielectric and energy storage properties of Pb(Tm1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3 antiferroelectric ceramics

In order to stabilize the perovskite structure and improve the storage energy density (U) of Pb(Tm_1/2Nb_1/2)O₃ (PTmN) based materials, Pb(Mg_1/3Nb_2/3)O₃ (PMN) was introduced into PTmN to form binary (1-x)PTmN-xPMN solid solution ceramics. The XRD patterns show that all the compositions belong to orthorhombic phase with space group Pbnm. The Curie temperature (T_C) gradually decreases while the dielectric constant (ε') increases for (1-x)PTmN-xPMN with increasing PMN content. The ε' of each composition above T_C obeys the Curie-Weiss law. The appearance double hysteresis loop confirms the antiferroelectric nature of (1-x)PTmN-xPMN (x = 0.02–0.18) ceramics. With the increase of PMN concentration, the maximum polarization slowly increases from 8.58 μC/cm² to 29.5 μC/cm² while the threshold electric field (E_A-F) gradually declines from 290 kV/cm to 120 kV/cm. The maximum of U (3.12 J/cm³) is obtained in 0.92PTmN-0.08PMN ceramic with moderate E_A-F = 220 kV/cm, which makes (1-x)PTmN-xPMN ceramics safe in practical application.     

New evidence for rhombohedral symmetry in the relaxor ferroelectric Pb(Mg1/3Nb2/3)O3

Neutron diffraction data have been collected from powders of lead magnesium niobate (PMN) at 300 and 10 K, following their synthesis in an optimised two-step reaction. Subsequent Rietveld refinement indicates that macroscopic rhombohedral symmetry is obtained at both temperatures. Moreover, the existence of a polar structure at room temperature has been independently confirmed by second harmonic generation measurements. The derived crystal structures indicate R3m and R3c symmetry at 300 and 10 K, respectively. The significance of these results for an understanding of the mechanism of relaxor ferroelectricity in PMN is discussed. ©     

铌镁酸铅弛豫型铁电陶瓷的介电老化行为研究

通过典型弛豫型铁电陶瓷铌镁酸铅介电老化行为的研究,发现高温区的Debye型弛豫过程与介电老化现象存在有机联系,指出复合钙钛矿弛豫型铁电体的结构缺陷特征对其介电老化起着重要作用.介电极化行为与老化行为对比分析和恒温经时老化研究表明,结构缺陷上的局域化电子和空穴对铁电微畴畴壁"钉扎"效应产生弛豫型铁电体介电老化行为的快过程.     

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.     

部分草酸盐工艺制备Pb(Mg1/3Nb2/3)O3-PbTiO3铁电陶瓷

通过部分草酸盐工艺制备了颗粒尺寸较小、粒度分布较均匀、团聚较少的(1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3(PMN-PT)前驱体.以活性PMN-PT前驱体为原料,通过固相反应法制备PMN-PT陶瓷.XRD测量表明,通过部分草酸盐工艺制备的PMN-PT陶瓷中含有少量的焦绿石相.随着PbTiO3 (PT)含量的增加,PMN-PT陶瓷的晶体结构从三方铁电相逐渐向四方铁电相转变.烧成的PMN-PT陶瓷具有较高的致密度.组分和烧结温度对PMN-PT陶瓷的电学性能产生影响.随着烧结温度的升高,PMN-PT陶瓷的介电常数最大值εm增大,伴随着εm对应的温度Tc/Tm的不规律变化;剩余极化强度Pr增大,矫顽场Ec减小;压电应变常量d33值增大.随着PT含量的增加,Tc/Tm增大,介电响应特征从弥散型铁电相变向正常铁电相变转变,电滞回线从狭长的回线向接近矩形的形状转变.0.68PMN-0.32PT陶瓷呈现优良的综合电学性能,1200℃烧结的陶瓷1kHz时εm为14070,Tm为148.2℃,d33值为457pC/N,Pr为14.69μC/cm2,Ec为4.72kV/cm.     

Microwave properties of Ba(Mg1/3Ta2/3)O3, Ba(Mg1/3Nb2/3)O3 and Ba(Co1/3Nb2/3)O3 ceramics revealed by Raman scattering

Five Ba(Co_1/3Nb_2/3)O₃ samples sintered at different temperatures (form 1350 to 1550 °C), one Ba(Mg_1/3Ta_2/3)O₃ and a Ba(Mg_1/3Nb_2/3)O₃ sample were examined by Raman scattering to reveal the correlation of the 1:2 ordered perovskite structure with the microwave properties, such as dielectric constant and Q factors. The Ba(Co_1/3Nb_2/3)O₃ sample sintered at 1400 °C, which possesses the highest microwave Q value and the lowest dielectric constant among five Ba(Co_1/3Nb_2/3)O₃ samples, has the narrowest width and the highest frequency of the stretch mode of oxygen octahedron (i.e. A_1g(O) near 800 cm⁻¹). We found that the dielectric constant is strongly correlated with the Raman shift of A_1g(O) stretch modes, and the width of A_1g(O) stretch mode reflects the quality factor Q × f value in the 1:2 ordered perovskite materials. This concludes that the oxygen octahedron play an important role of the material's microwave performance. Based on the results of Q × f values and the lineshapes of A_1g(O) stretch mode, we found that the propagation of microwave energy in Ba(Mg_1/3Ta_2/3)O₃ and Ba(Mg_1/3Nb_2/3)O₃ shows weak damping behavior, however, Ba(Co_1/3Nb_2/3)O₃ samples sintered at different temperature exhibit heavily damped behavior.     

Effects of MgO Stoichiometry on the Dielectric and Mechanical Response of Pb(Mg1/3Nb2/3)O3

Careful control of the magnesia stoichiometry and hydration level overcomes the problem of pyrochlore formation in the synthesis of Pb(Mg_1/3Nb_2/3)O₃ (PMN). Careful removal of volatiles from MgO showed that excess MgO is not required to form pyrochlore-free PMN using the columbite method; this clarifies the previously reported need of excess MgO. The stoichiometric PMN shows a peak dielectric constant of ~15 000 for 1 kHz. In addition, the presence of volatiles in the MgO has been linked with a change in fracture mode. The relation between the MgO stoichiometry and the microstructural and dielectric properties is presented in an integrated study using X-ray diffraction at various temperatures, dielectric response, and microscopy.     

ZnO-activated formation of phase pure perovskite Pb(In1/2Nb1/2)O3-Pb(Zn1/3Nb2/3)O3-PbTiO3 powder

This paper reports on the phase formation of perovskite Pb(In_1/2Nb_1/2)O₃-Pb(Zn_1/3Nb_2/3)O₃-PbTiO₃ (PIN-PZN-PT) powder when doped with 0.04 to 0.83 mol% ZnO. Air calcination of undoped powder mixtures for 4 hours at 800°C resulted in a mixture of Pb₂Zn_0.29Nb_1.71O_6.565 pyrochlore, PIN-PZN-PT perovskite, and In₂O₃. ZnO dopant concentrations as low as 0.04 mol% increased the rate of perovskite formation and resulted in near phase pure perovskite powder of 0.5 μm particle size when heated at 800°C in air. In all cases PbTiO₃ and Pb(In_1/2Nb_1/2)O₃ formed prior to PIN-PZN-PT formation. ZnO doping promotes perovskite phase formation by increasing the reactivity of the intermediate pyrochlore phase by substituting Zn²⁺ on Nb⁵⁺ sites and forming oxygen vacancies when heated in air. Heating in high resulted in an incomplete reaction and a mixture of perovskite and pyrochlore whereas low resulted in phase separation into a mixture of rhombohedral perovskite, tetragonal perovskite, and pyrochlore. The sensitivity clearly shows that oxygen vacancies due to ZnO-doping are critical for synthesis of phase pure PIN-PZN-PT powder.     

Effect of electric field on domain formation in relaxor based Pb(Zn1/3Nb2/3)O3 - PbTiO3 single crystals

Domain switching has been observed in 0. 9PZN - 0. 1PT single crystals under the influence of electric field. The crystal being near the morphotropic phase boundary contains two phases - rhombohedra1 and tetragonbal. The electric field was applied along two principal directions [001] and [111]. Their formation as the temperature is reduced with the electric field is discussed here. For electric field along [001]. it was found that a single domain could be induced in tetragonal phase. When the electric field was applied along [111], the formation of domains as temperature is reduced are shown to be remarkably similar to those formed when the temperature is fixed and the concentration of IT varied. This type of domain hierarchy may be a contributing factor for the high k (electromechanical factor) observed in these crystals.     

Structural Evolution and Properties of 0.3Pb(In1/2Nb1/2)O3–0.38Pb(Mg1/3Nb2/3)O3–0.32PbTiO3 Ferroelectric Ceramics with Different Sintering Times

The structural evolution and properties of 0.3Pb(In_1/2Nb_1/2)O₃–0.38Pb(Mg_1/3Nb_2/3)O₃–0.32PbTiO₃ (0.3PIN‐0.38PMN‐0.32PT) ferroelectric ceramics with different sintering times have been investigated. The content of the tetragonal phase is increased in samples sintered for more than 6 h, despite that the composition falls in the rhombohedral region of the previously established phase diagram. The results show that the metastable tetragonal phase at room temperature is induced and stabilized by the tensile residual stresses. Excessively long sintering time generally leads to grain coarsening, loss of lead, and deterioration of properties, while the increasing amount of the tetragonal phase, and the large residual tensile stress appear to improve the dielectric and electromechanical properties. This study offers new insights into the sintering of Pb‐based ferroelectric ceramics with complex compositions.     

Processing and properties of 0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 thick films

We have investigated the processing of 0.65Pb(Mg_1/3Nb_2/3)O₃–0.35PbTiO₃ (PMN–PT) thick films on platinised alumina substrates. Nanosized PMN–PT powder with 2 mol% of excess PbO was prepared by high-energy milling and deposited on the substrate using screen-printing technology. The films were then sintered at 950 °C in a PbO-rich atmosphere. The influence of the sintering time and the amount of PbO-containing packing powder was studied and related to the structural, microstructural, dielectric and piezoelectric properties of the film. In order to obtain a homogeneous and dense thick film without any secondary phase, the PMN–PT films had to be sintered in the presence of a PbO-based liquid phase that had to be completely removed from the thick film during the final stage of the sintering. Under optimal sintering conditions we obtained a room temperature relative dielectric permittivity of 3600, dielectric losses of 0.036, a T_m of 174 °C, a permittivity at the T_m of 21,000 and a d₃₃ of 140 pC/N.