等静压下0.75Pb（Mg1/3Nb2/3）O3-0.25PbTiO3陶瓷的介电性能研究

研究了等静压对0.75Pb（Mg_1/3Nb_2/3）O₃-0.25PbTiO₃（PMN-25PT）陶瓷介电温谱的影响,PMN-25PT剩余极化随等静压变化和等静压压致相变.结果表明,随着压力增加,PMN-25PT的介电峰值温度T_m降低,/+{dT_m}/-{dP}≈-4℃/kbar,极化弛豫增强;剩余极化随压力增加连续减小;介电常数对压力的依赖关系与对温度场的依赖相似,压力诱导PMN-25PT发生弛豫铁电—顺电相变,相变为宽化的渐变过程,频率色散和极化弛豫更加强烈和普遍. 关键词： 铌镁酸铅-钛酸铅 等静压 介电弛豫 压致相变     

The transverse laser induced thermoelectric voltages in step flow growth （1-x）Pb(Mg1/3Nb2/3)O3-xPbTiO3 thin films

This paper reports that the transverse laser induced thermoelectric voltages (LITV) are observed for the first time in the step flow growth (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT,x = 0.20, 0.33, 0.50) thin films deposited on vicinal-cut strontium titanate single crystal substrates. Because lead magnesium niobate-lead titanate is a solid solution of lead magnesium niobate (PMN) and lead titanate (PT), there are two types of signals. One is wide with a time response of a microsecond, and the other superimposed with the wide signal is narrow with a time response of a nanosecond. The transverse LITV signals depend on the ratio of PMN to PT drastically. Under the irradiation of 28-ns pulsed KrF excimer laser with the 248-nm wavelength,the largest induced voltage is observed in the 0.50Pb(Mg1/Nb2/3)O3-0.50PbTiO3 films. Moreover, the effects of film thickness, substrates, and tilt angles of substrates are also investigated.     

Piezoelectric properties of PbHfO3–PbTiO3–Pb(Mg1/3Nb2/3)O3 ternary ceramics

(1 – x)Pb(Hf_1–yTi_y)O₃–x Pb(Mg_1/3Nb_2/3)O₃ (x = 0.1 ～ 0.25, y = 0.555) ternary piezoelectric ceramics were prepared using the two‐step precursor method. Morphotropic phase boundary (MPB) compositions, located at x = 0.18 ～ 0.22, were confirmed using X‐ray diffraction and by their dielectric, piezoelectric and ferroelectric properties. The optimum dielectric and piezoelectric properties were achieved for the MPB composition 0.8Pb(Hf_0.445Ti_0.555)O₃–0.2Pb(Mg_1/3Nb_2/3)O₃, with dielectric permittivity ε_r, piezoelectric coefficient d₃₃, planar electromechanical coupling k_p and Curie temperature T_C being on the order of 2800, 680 pC/N, 70% and 276 °C, respectively. Of particular significance is that the new ternary ceramics exhibit comparable piezoelectric and electromechanical properties to commercial PZT5H ceramics, but with much improved T_C, showing a potential for applications at elevated temperature. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Electric field effects on the dielectric and acoustic anomalies of Pb[(Mg1/3Nb2/3)0.83Ti0.17]O3 single crystals studied by dielectric and Brillouin spectroscopies

The effect of the electric field on the dielectric and acoustic properties of Pb[(Mg_1/3Nb_2/3)_0.83Ti_0.17]O₃ single crystals was investigated as functions of temperature and the electric field strength. The dielectric constant and the acoustic mode behaviors exhibited typical relaxor behaviors when there was no bias field. The longitudinal acoustic mode showed splitting under a moderate electric field of 1 kV/cm applied along the [001] direction, indicating coexistence of macroscopic/mesoscopic ferroelectric states and relaxor states. Further increase in the electric field up to 2 kV/cm induced a clear ferroelectric phase transition, which became smeared out due to the proximity of the electric field to the critical point. The electric field-temperature phase diagram of Pb[(Mg_1/3Nb_2/3)_0.83Ti_0.17]O₃ was suggested based on the observed field-induced changes in the dielectric and the acoustic properties.     

Predominant factors affecting the dielectric and piezoelectric properties of bismuth-containing complex perovskite solid solution

To study the factors affecting the dielectric and piezoelectric properties of bismuth-containing complex perovskites, the solid solution (1−x)Pb(Mg_1/3Nb_2/3)O₃-xBi(Mg_2/3Nb_1/3)O₃ was prepared by the solid state reaction method and its dielectric and piezoelectric properties were investigated. It is found that (1) at room temperature, the nonlinearity of the DE-loop for Pb(Mg_1/3Nb_2/3)O₃ is completely suppressed at a rather low x (<5%); (2) dielectric constant versus temperature curves deviate from the Curie-Weiss law at a temperature T_d much higher than the dielectric constant peak temperature T_m and T_m−T_d decreases considerably with increasing x; and (3) frequency dispersion ΔT_m=T_m (1 MHz)−T_m (10 kHz) increases with increasing x. Possible factors responsible for the variation of the dielectric and piezoelectric properties with x are discussed.     

Electric field induced ferroelectricity in PbBO3 perovskites with complex substitution in the B position

Processes of the polarization switching in ceramic relaxors Pb(Mg_1/3Ti_1/3W_1/3)O₃, Pb(Mg_1/4Sc_1/4Nb_1/4W_1/4)O₃, Pb(Mg_1/5Sc_1/5Ti_1/5Nb_1/5W_1/5)O₃, and Pb(Mg_1/6Sc_1/6Ti_1/6Sn_1/6Ta_1/6W_1/6)O₃ have been investigated at frequencies from 50 Hz to 2 kHz in the temperature range 90–300 K for measuring field amplitudes up to 20 kV/cm. It has been demonstrated that, under specific conditions, these materials are characterized by saturated dielectric hysteresis loops, which indicate the appearance of the ferroelectric state induced by the electric field. The dependences of the spontaneous polarization and the coercive field of the relaxors under investigation on their chemical composition, temperature, and frequency of the measuring voltage have been determined.     

Dielectric and piezoelectric properties of manganese‐modified PbHfO3–PbTiO3–Pb(Mg1/3Nb2/3)O3 ternary ceramics with morphotropic phase boundary compositions

High piezoelectric and electromechanical properties were reported in the PbHfO₃–PbTiO₃–Pb(Mg_1/3Nb_2/3)O₃ ternary system with morphotropic phase boundary (MPB) compositions. This work focuses on the effect of MnO₂ addition on 0.8Pb(Hf_0.443Ti_0.557)O₃–0.2PMN (0.8PHT–0.2PMN) ceramics. It was observed that the Mn acceptor modification induced a “hardening” effect in 0.8PHT–0.2PMN, with decreased piezoelectric coefficients d₃₃ and dielectric loss tan δ and a significantly increased mechanical quality factor Q_m. Moreover, the 0.2 wt% MnO₂‐doped 0.8PHT–0.2PMN ceramics exhibited good piezoelectric and electromechanical properties with d₃₃, planar electromechanical coupling k_p and Q_m being on the order of 360 pC/N, 61% and 700, respectively, showing advantages compared to those of commercial hard PZT4 ceramics, which is attractive for high power applications. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A comparative study of dielectric and Raman spectroscopy of Pb(Y b1/2Ta1/2)O3 and Pb(Y b1/2Nb1/2)O3

A comparative study of the properties of two highly ordered lead based complex perovskites Pb(Y b_1/2Ta_1/2)O₃ and Pb(Y b_1/2Nb_1/2)O₃ has been carried out through x-ray diffraction, dielectric and Raman scattering measurements. These two compounds differ significantly in their structure, dielectric response and phonon vibration although the ionic radii and valencies are same for Ta and Nb. The room temperature x-ray diffraction pattern and Raman spectra show that the symmetry of lead ytterbium tantalate is lower than that of lead ytterbium niobate. The Raman spectra of Pb(Y b_1/2Ta_1/2)O₃ also indicates the presence of local distortion in the lattice which may be one of the factors responsible for the existence of a secondary transition.     

Giant dielectric relaxation in SrTiO3-SrMg1/3Nb2/3O3 and SrTiO3-SrSc1/2Ta1/2O3 solid solutions

Ceramic samples of (1−x)SrTiO₃-xSrMg_1/3Nb_2/3O₃ and (1−x)SrTiO₃-xSrSc_1/2Ta_1/2O₃ were prepared, and their dielectric properties were studied at x=0.005–0.15 and 0.01–0.1, respectively, at frequencies 10 Hz–1 MHz and at temperatures 4.2–350 K. A giant dielectric relaxation was observed in the temperature range 150–300 K, and not so strong but well-developed relaxation was found in the temperature range 20–90 K. The activation energy U and the relaxation time τ₀ were determined to be 0.21–0.3 eV and from 10⁻¹¹ to 10⁻¹² s for the high-temperature relaxation and 0.01–0.02 eV and 10⁻⁸–10⁻¹⁰ s for the low-temperature relaxation, respectively. The additional local charge compensation of the heterovalent impurities Mg²⁺ and Nb⁵⁺ (or Sc³⁺ and Ta⁵⁺) by free charge carriers or the host ion vacancies is suggested to be the underlying physical mechanism of the relaxation phenomena. On the basis of this mechanism, the Maxwell-Wagner model and the model of reorienting dipole centers Mg²⁺ (or Sc³⁺) associated with the oxygen vacancy are proposed to explain the high-temperature relaxation with some arguments in favor of the latter model. The polaron-like model with the Nb⁵⁺-Ti³⁺ center is suggested as the origin of the low-temperature relaxation. The reasons for the absence of ferroelectric phase transitions in the solid solutions under study are also discussed. From Fizika Tverdogo Tela, Vol. 44, No. 11, 2002, pp. 1948–1957. Original English Text Copyright ? 2002 by Lemanov, Sotnikov, Smirnova, Weihnacht. This article was submitted by the authors in English.     

Low- and infralow-frequency dielectric properties of the Pb(Mg1/3Nb2/3)O3 + 2 wt % Li2O ceramics

A dielectric response of the Pb(Mg_1/3Nb_2/3)O₃ ferroelectric ceramics with impurity of 2 wt % Li has been studied. The phase transition has been found to exhibit a relaxor character, as is the case in PMN without Li. However, unlike pure PMN, the dielectric response dispersion in PMN + 2 wt % Li₂O has been described by the Cole-Cole equation at temperatures below the temperature of the low-frequency maximum of the permittivity. An analysis of the dispersion parameters in a wide temperature range has demonstrated that it can be due to the relaxation of domain walls in PMN + 2 wt % Li₂O that appear most likely because of the existence of anomalously coarse grains in PMN + 2 wt % Li₂O.     

Properties of (Bi1/9Na2/3)(Mn1/3Nb2/3)O3 analysed within dielectric permittivity,conductivity, electric modulus and derivative techniques approach

The (Bi_1/9Na_2/3)(Mn_1/3Nb_2/3)O₃ ceramics with perovskite structure were sintered. The XRD test proved that the samples are cubic (a?=?3.920?±?0.001?Å). Microstructure and atomic composition were determined with a SEM (JSM-5410) equipped with energy dispersion X-ray analyser (ISIS-300). The fluctuation in the chemical composition was found indicating on local disorder. Broadband dielectric spectroscopy in the range 10^?1–3?·?10⁷?Hz was applied within the range of 100–650?K. The real, ?′(f,?T), and imaginary, ?″(f,?T), parts of complex dielectric permitivity characteristics, both in the temperature and frequency domain, show relaxation processes partially covered by electric conductivity. At high temperatures the electric conductivity exhibits a thermally activated behaviour σ(f,?T)?∝?exp(?E _a/kT) but the variable range hopping (VRH) dependence σ?∝?exp[?(T ₀/T)^1/4] is manifested at low temperatures. The derivatives technique in the frequency (??log??/??log?ω) and temperature (??log??/?T) domain enabled various relaxation processes to be distinguished. The data converted to electric modulus representation, M*(f,?T)?=?1/?*, exhibited clearly resolved relaxation peaks. The relaxation times obtained from the peaks position show a slightly non-Arrhenius temperature behaviour with the activation energy varying in 0.4–0.6?eV range and characteristic time of the electric conductivity relaxation of the order of 10^?12?s. The relaxation times can be fitted at better accuracy with the VRH dependence where T ₀ are of the order of 10⁸?K. It is shown that the low frequency ac-conductivity converges to dc-conductivity and the relation σ(0)?～?ω_m?～?τ_m ^?1 typical for the disordered solids applies. The conduction current relaxation relationship behaves in accord with the VRH system: σ_dc?∝?(T/T ₀)^q (e ²/kT) ω_c, where ω_c?=?ν_ph exp[?(T ₀/T)^1/4] is valid for the locally disordered (Bi_1/9Na_2/3)(Mn_1/3Nb_2/3)O₃ compound.     

The role of the secondary pyroelectric effect in a ferroelectric relaxor 0.72Pb(Mg<Subscript>1/3</Subscript>Nb<Subscript>2/3</Subscript>)O<Subscript>3</Subscript>-0.28PbTiO<Subscript>3</Subscript>

The depth profile of the pyroelectric coefficient effective values of a 0.72Pb(Mg_1/3Nb_2/3)O₃-0.28PbTiO₃ (PMN-0.28PT) single crystal is studied. It was shown that owing to high pyroelectric coefficients the secondary pyroelectric effect significally contributes (∼40%) to the total pyroelectric coefficient.     

Dielectric response of disordered Pb(Sc1/2Ta1/2)O3 single crystal under hydrostatic pressure

The effect of hydrostatic pressure on the dielectric response of Pb(Sc_1/2Ta_1/2)O₃ single crystal with the degree of order S = 0.16 has been studied. At elevated pressures the dielectric anomaly characteristic of ferroelectric relaxors is shifted to lower temperatures, its amplitude decreases and the relaxor peak becomes more diffused. In the pressure range studied up to 0.75 GPa, the temperature dependencies of the characteristic relaxation time obey the Vogel–Fulcher law. It has been found that the Vogel–Fulcher temperature decreases with increasing pressure while the activation energy of the dipolar entities increases. This increase can be ascribed to the pressure-induced changes in the atom–atom and dipolar interactions, resulting in the increased energy barriers for dipolar fluctuations.     

Effects of strontium on the characteristics of Pb(Zr1/2Ti1/2)O3--Pb(Zn1/3Nb2/3)O3 ceramics

The dielectric and piezoelectric properties of pyrochlore-free lead zirconate titanate-lead zinc niobate ceramics were investigated systematically as a function of Sr doping. The powders of Pb_{(1? x )}Sr _x [0.7(Zr_{1 / 2}Ti_{1 / 2})–0.3(Zn_{1 / 3}Nb_{2 / 3})]O₃, where x?=?0–0.06 were prepared using the columbite-(wolframite) precursor method. The ceramic materials were characterized using X-ray diffraction, dielectric spectra, hysteresis and electromechanical measurements. The phase-pure perovskite phase of Sr-doped PZN--PZT ceramics was obtained over a wide compositional range. The results showed that the optimized electrical properties were also achieved at composition x?=?0.0, which were K _P?=?0.69, d ₃₃?=?670?pC?N^?1, P _r?=?31.9?µC?cm^?2 and ε_rmax?=?18600. Maximum dielectric constant values of the systems decreased rapidly with increasing Sr concentration. Moreover, with increasing Sr concentration dielectric constant versus temperature curves become gradually broader. The diffuseness parameter increased significantly with Sr doping. Furthermore, Sr doping has been shown to produce a linear reduction in the transition temperature (T _m)?=?294.1–12.7x°C with concentration (x). Sr shifts the transition temperature of this system at a rate of 12.7°C?mol^?1%.     

Phase transitions in solid solutions (1 ? x)BaTiO3-xBaMg1/3B2/3O3 (B = Nb, Ta)

The dielectric properties of ceramic samples of (1 − x)BaTiO₃-xBaMg_1/3Nb_2/3O₃ and (1 − x)BaTio₃-xBaMg_1/3Ta_2/3O₃ solid solutions (x = 0–0.25) are investigated in the frequency range from 10 Hz to 100 kHz at temperatures of 77–450 K. It is shown that the (x−T) phase diagrams of these solid solutions at x = 0.05 have a multiphase point at which the lines of all three phase transitions of BaTiO₃ converge. Original Russian Text ? V.G. Zalesskiĭ, V.V. Lemanov, E.P. Smirnova, A.V. Sotnikov, N. V. Zaĭtseva, 2007, published in Fizika Tverdogo Tela, 2007, Vol. 49, No. 1, pp. 108–112.     

Equivalent magnetic noise in magnetoelectric Metglas/Pb(Mg1/3Nb2/3)O3‐PbTiO3 laminate composites

We have experimentally and theoretically investigated the equivalent magnetic noise in a magnetoelectric Metglas/ 0.7Pb(Mg_1/3Nb_2/3)O₃‐0.3PbTiO₃ laminate sensor unit by considering the constituent noise sources of dielectric loss (N_DE) and DC leakage resistance (N_R). In the low frequency range (f = 1 Hz), theory predicts that N_R dominates the noise charge (1.6 times larger than N_DE), with a 1 Hz noise of 9.1\;{\rm pt}/\sqrt {\rm Hz}. The experimental equivalent magnetic noise was 10.8\;{\rm pt}/\sqrt {\rm Hz}. This observed value is slightly higher than the predicted one, which might be due to an oversimplification of the theoretical model in terms of electrical charge amplifier and external vibration noise sources. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

铁电磁体Pb(Fe1/2Nb1/2)O3的磁电性能研究

对铁电磁体Pb(Fe_1/2Nb_1/2)O₃单晶样品中的 介电和磁性能进行了研究. 认为在其反铁磁相变点观察到的介电常数和损耗的异常来自于自发极化序和自旋序的相互作用 引起的磁电耦合. 磁矩与温度的关系曲线在Nel点以下的低温段呈上升趋势，测得的磁滞 回线证明有弱铁磁性出现. 对铁电磁体磁电相互作用的Monte Carlo模拟得到与实验类似的 结果. 关键词： 铁电磁体 1/2Nb_1/2)O₃')" href="#">Pb(Fe_1/2Nb_1/2)O₃ 磁电耦合 Monte Carlo模拟     

Pb-driven anti-ferroelectric phase in Pb(Mg1/3Nb2/3)O3 : First-principle study

Density functional calculations are used to investigate the role of Pb displacement in the formation of anti-ferroelectric phase in Pb(Mg_1/3Nb_2/3)O₃. Order and disordered supercells, both are used. Through geometry optimization without symmetry imposed, the two supercells are found to be anti-ferroelectric. Displacement of cations are analyzed and it is shown that asymmetry of Pb’s next-nearest B-site shell is probably the reason for anti-parallel displacement of Pb. A–B-site, B-site–O bond distances and O₆ octahedral volumes are also calculated.     

Combinatorial processing libraries for bulk BiFeO3–PbTiO3 piezoelectric ceramics

A high throughput approach for generating combinatorial libraries with varying processing conditions for bulk ceramics has been developed. This approach utilized the linear temperature gradient in a tube furnace to screen a whole temperature range for optimized preparation. With this approach, the processing of 0.98[0.6BiFeO₃–0.4PbTiO₃]–0.02Pb(Mg_1/3Nb_2/3)O₃ ceramic powders and pellets for high-temperature piezoelectric applications was demonstrated to identify the best synthesis conditions for phase purity. The dielectric property measurement on the as-processed solid solution ceramics confirmed the high Curie temperature and the improved loss tangent with the Pb(Mg_1/3Nb_2/3)O₃ doping.     

Microstructure and properties of Pb(Mg1/3Nb2/3)O3–Portland cement composites

Lead magnesium niobate, Pb(Mg_1/3Nb_2/3)O₃ (PMN), ceramics particles was mixed with Portland Cement (PC) using a water to cement ratio of 0.50 and PMN content at 40% and 60% by weight to produce 0–3 Pb(Mg_1/3Nb_2/3)O₃–Portland cement (PMN–PC) composites. Microstructure and hydration of the composites were investigated. Calcium silicate hydrate gel can be seen surrounding the PMN particles. Dielectric constant of the composites was found to increase with PMN content. Successful poling of the composites was achieved. Interestingly, SEM micrographs of the PMN40 composite clearly showed calcium silicate hydrate gel (an essential hydration product of Portland cement) surrounding the PMN particles. In PMN60 composite, the gel can also still be seen but of less quantity. This is thought to be due to the increase in the volume ratio of the ceramics where the amount of calcium silicate hydrate gel was reduced in relation to the overall volume.