Ferroelectric properties of Pb(Zr1/2Ti1/2)O3–Pb(Zn1/3Nb2/3)O3 ceramics under compressive stress

Effects of compressive stress on the ferroelectric properties of ceramics in PZT–PZN system were investigated. The ceramics with a formula (1−x)Pb(Zr_1/2Ti_1/2)O₃–xPb(Zn_1/3Nb_2/3)O₃ or (1−x)PZT–(x)PZN (x = 0.1–0.5) were prepared by a conventional mixed-oxide method. The ferroelectric properties under the compressive stress of the PZT–PZN ceramics were observed at the stress levels up to 170 MPa using a compressometer in conjunction with a modified Sawyer–Tower circuit. It was found that with increasing compressive stress the area of the ferroelectric hysteresis (P–E) loops, the saturation polarization (P_sat), the remnant polarization (P_r), and the coercive field (E_c) decreased. These results were interpreted through the non-180° ferroelastic domain switching processes.     

Synthesis and electrical properties of Pb(Mg1/3Nb2/3)O3–PbTiO3 ceramics

Ceramic compositions of a combination between lead magnesium niobate, Pb(Mg_1/3Nb_2/3)O₃, and lead titanate, PbTiO₃, were fabricated by using Mg₄Nb₂O₉ precursor technique. Their electrical properties with respect to temperature and frequency were examined and the effect of sintering conditions on phase formation, densification, microstructure and electrical properties of the ceramics were examined. It has been found that optimisation of sintering condition can lead to a highly dense and pyrochlore-free PMN–PT ceramics. The gradual decreasing of the physical properties of the sintered ceramics was related to the gradual decrease of density and inhomogeneous microstructure. The results also revealed that for the lower concentration of lead titanate a relaxor behavior is noticed with a high electrostrictive effect, which was almost hysteretic free. However, higher amount of lead titanate led to a normal ferroelectric behavior.     

Dielectric Response of Ceramic 16BiScO3–42PbMg1/3Nb2/3O3–42PbTiO3 Solid Solutions in an Electrical Field

Physics of the Solid State - Some results of studying the dielectric and electromechanical properties of ceramic 16BiScO3–42PbMg1/3Nb2/3O3–42PbTiO3 relaxor ferroelectric samples in...     

Elastic–plastic deformation of Pb(Zn1/3Nb2/3)O3–(6–7)% PbTiO3 single crystals during nanoindentation

The elastic–plastic deformation behavior of (001)- and (011)-oriented single crystal solid solutions of Pb(Zn_1/3Nb_2/3)O₃–(6–7)% PbTiO₃ (PZN–PT) have been studied using a nanoindentation technique. A procedure is presented here to isolate the elastic, elastic–plastic and plastic contributions to the deformation using the unloading data, and a parameter, referred to as relaxation, is defined to characterize the elastic–plastic deformation during nanoindentations. This relaxation parameter increases with the maximum indentation load due to the higher indentation stress induced, and it also causes less recovery of the material upon indentation unloading compared to predicted pure elastic recovery. For a (001) surface, the relaxation value remains virtually unchanged within the range of the maximum indentation load of 10–50 mN, possibly due to a complete localized depoling of the non-180° domain switching. It is also found that the unpoled surface is more prone to stress-induced depolarization compared to the poled surfaces. Furthermore, by applying the continuous stiffness measurement (CSM) technique, the effects of multiple loading/unloading are studied for both (001)- and (011)-oriented PZN–PTs using the maximum indentation loads of 20 and 50 mN. With more loading/unloading cycles at higher CSM frequencies, stress-induced depolarization becomes prevalent and the contribution of the domain reorientation towards elastic recovery is significantly reduced. As a consequence, the relaxation value is increased, indicating more elastic–plastic deformation. This CSM effect is especially pronounced for poled (011) surfaces.     

Polarization Kinetics in Transparent Pb(Mg1/3Nb2/3)O3–23Pb(Zr0.53Ti0.47)O3 Ceramic

Physics of the Solid State - The polarization kinetics in a transparent Pb(Mg1/3Nb2/3)O3–23Pb(Zr0.53Ti0.47)O3 ferroceramic is investigated in the electric fields of 0 < E < 6...     

0.67 PbMg1/3Nb2/3O3-0.33 PbTiO3单晶中软模模式指认

应用显微拉曼技术对弛豫型铁电体0.67PbMg1/3Nb2/3O3-0.33PbTiO3(0.67PMN-0.33PT)的偏振拉曼光谱随温度变化的研究表明,在-196到600°C温度范围内0.67PMN-0.33PT存在两次相变:三方到四方(R-T)相变和四方到立方(T-C)相变。R-T相变的特征是106cm-1软模(-196°C时)随温度的升高而湮没到80cm-1"静态"模式中。依照群论分析,0.67PMN-0.33PT的80cm-1和106cm-1(-196℃时)两个模式分别为E(1TO)和A1(1TO)模。文章对三方相的对称结构(C3v点群)在背向散射配置下不同偏振方向的拉曼散射效率进行了计算。计算结果表明晶体中的A1(1TO)和E(1TO)模式能够通过使用不同的散射配置进行识别。理论计算和实验结果相比较得到了很好的吻合。     

Pb(Mg1/3Nb2/3)O3-PbTiO3/CoFe2O4复合薄膜 电学、磁学性能的研究

利用射频磁控溅射技术在LaNiO3/SiO2/Si基底上制备了Pb(Mg1/3Nb2/3)O3-PbTiO3/CoFe2O4和Pb(Mg1/3Nb2/3)O3-PbTiO3/CoFe2O4/Pb(Mg1/3Nb2/3)O3-PbTiO3两种复合薄膜.我们采取了三种退火条件对复合薄膜进行退火处理,研究两种复合薄膜的晶体结构、电学和磁学性能.通过对两种复合薄膜的结构的分析,发现两步法退火后得到复合薄膜同时存在纯钙钛矿相和尖晶石相两种结构.铁电性能测试表明:两种复合薄膜均具有较好的铁电性能,其中三层复合薄膜的剩余极化强度Pr最大可以达到14.9 μC/cm2,这要归因于多层复合薄膜内部的应力-应变效应和界面耦合效应.在电场强度为80kV/cm的漏电流密度数量级仅10-5A/cm2,其导电机制在高电场区满足Schottky机制.介频性能测试表明:复合薄膜的介频特性较差,双层复合薄膜的介电性能较好,其介电常数εr为1078,其介电损耗tgδ较大,约为0.43.此外,对复合薄膜的磁滞回线测试表明:两种复合薄膜中均存在磁学性能,且双层结构复合薄膜的铁磁性能较大,其饱和磁化强度Ms为119 emu/cm3,剩余磁化强度Mr达到31.6 emu/cm3,矫顽场Hc为1360 Oe. 以上测试结果表明,铁电有序和磁有序可以存在于钙钛矿-尖晶石结构当中,通过多层复合和合适退火方式可以增强其铁电和介电性能.     

铁电磁体Pb(Fe1/2Nb1/2)O3的磁电性能研究

对铁电磁体Pb(Fe1/2Nb1/2)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Néel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.     

A longitudinal (1−x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 single-crystal piezoelectric transformer

In present work, a simple longitudinal piezoelectric transformer with the size of 16-mm length, 2-mm width, and 2-mm thickness was designed and fabricated with relaxor ferroelectric single-crystal (1−x)Pb(Mg_1/3Nb_2/3)O₃-xPbTiO₃. Both the input and output parts utilized the ultrahigh longitudinal extensional electromechanical coupling coefficients. Compared to the Rosen-type transformer, this transformer has the advantages of smaller-size, simpler structure, no spurious vibration, and no acoustic mismatch between the input and output parts. The electrical measurement results indicated that under the resonance frequency of 114 kHz, a step-up voltage of about 30 can be obtained under a 10-MΩ load resistance, which agreed well with the calculated results. Besides, the frequency and load dependences of this transformer were also systematically studied and discussed. The results indicated that this transformer has potential applications in the small-size high-voltage amplifier and magnetoelectric/piezoelectric-transformer composite transducers.     

Effects of Zr/Ti ratio on dielectric and ferroelectric properties of 0.8Pb(ZrxTi1−x)O3–0.2Pb(Co1/3Nb2/3)O3 ceramics

The influences of Zr/Ti ratio on electrical properties of the 0.8Pb(Zr_xTi_1−x)O₃–0.2Pb(Co_1/3Nb_2/3)O₃ ceramics prepared by a mixed-oxide method (with x = 0.46, 0.48, 0.50, 0.52, and 0.54) have been investigated in order to identify the morphotropic phase boundary composition in this system. With XRD analysis, the crystal structure of dense specimens appeared to change gradually from tetragonal to rhombohedral with increasing Zr content. The dielectric properties measurements showed a maximum dielectric constant at x = 0.50, while the transition temperature decreased with increasing Zr content in the system. Moreover, all ceramics showed diffused phase transition behaviors with a minimum diffusivity at x = 0.50. In addition, the Polarization–Electric field (P–E) hysteresis loops of the ceramic systems also changed significantly with the Zr content. Interestingly, the loop squareness parameter reached maximum around x = 0.50. Other ferroelectric hysteresis parameters showed noticeable change at x = 0.50. These results clearly showed the significance of Zr/Ti ratio in controlling the electrical properties of the PZT–PCN ceramic systems.     

Electric-field-induced tetragonal phase in [Pb(Mg1/3Nb2/3)O3]0.68–[PbTiO3]0.32 by Raman scattering

ABSTRACT

The paper describes investigation of the electric-field-induced phase transition in PMN-xPT single crystals with x = 0.32 by means of detailed polarized Raman scattering measurements. Field-induced tetragonal state was reached by applying an electric field up to 30 kV/cm along pseudo-cubic direction at a temperature slightly below that of the zero-field rhombohedral–tetragonal phase transition (T_RT). In this field-induced tetragonal state, the angular dependencies of the polarized Raman spectra were recorded and compared with the similar data available for the rhombohedral single-domain and multidomain states.     

铁电单晶0.62Pb(Mg1/3Nb2/3)O3-0.38PbTiO3折射率的研究

用最小偏向角法在20℃下精确测量了0.62Pb(Mg1/3Nb2/3)O3-0.38PbTiO3(0.62PMN-0.38PT)单晶的折射率,给出了该温度下折射率色散的Sellmeier方程.研究了能带结构与折射率的关系,计算了样品的Sellmeier光学系数:对no,E0=5.50eV,λ0=0.226μm,S0=1.004×1014m-2,Ed=28.10eV;对ne,E0=5.57eV,λ0=0.223μm,S0=1.017×1014m-2,Ed=28.10eV.ABO3型钙钛矿材料中,BO6八面体基元决定了晶体的能带结构,对折射率产生重要影响.     

Internal-friction study of the interstitial–substitutional effect on the deformation behaviour of Nb–O,Nb–Ta–O and Nb–Mo–O single crystals

To investigate the interstitial-substitutional interaction in dislocations, the effect of 0 on the temperature, frequency and amplitude dependence of the internal friction Q ^?1 in Nb–O, Nb-20 mol% Ta–O and Nb-20 mol% Mo–O single crystals has been studied (f = 1.55–8.2 Hz) in the temperature range from 298 to 1473 K. In our previous study, Nb–Mo and Nb–Ta single crystals were found to be strengthened by solute O. It was also suggested that the interstitial–substitutional interaction in dislocations contributes to the increase in their critical resolved shear stress (CRSS). In this study, Snoek-type relaxation peaks due to O are observed between 500 and 700 K in all the single crystals. The Snoek peak of Nb-20mol% Mo–O consisting of several peaks is analysed. The activation energy of the Snoek peak in Nb-20mol% Mo–O is higher than that of Nb–O. These results are attributable to the existence of the interstitial–substitutional complexes. The amplitude dependence of Q ^?1 at intermediate and high temperatures decreases as the O content increases. Moreover, the breakaway stress of Nb-20 mol% Mo–O still has a high value at 1200K and does not decrease much even at 1473 K. This suggests that the formation of Mo–O complexes reduces the dislocation mobility at high temperatures. From the results, the effect of the interstitial-substitutional interaction on the CRSS was discussed.     

Specific Features of the Local Structure and Transport Properties of ZrO2–Sc2O3–Y2O3 and ZrO2–Sc2O3–Yb2O3 Crystals

Optics and Spectroscopy - The specific features of the local structure of ZrO2–Sc2O3–Y2O3 and ZrO2–Sc2O3–Yb2O3 crystals are revealed by optical spectroscopy using the Eu3+...     

Dielectric properties and specific heat of the (1 ? x)PbNi1/3Nb2/3O3-xPbTiO3 ferroelectric ceramics

The temperature dependences of the permittivity and specific heat of a mixed (1 ? x)PbNi_1/3Nb_2/3O₃-xPbTiO₃ system (where x = 0.3, 0.4, 0.5) have been studied over a wide temperature range 290?C700 K. It has been shown that the composition with x = 0.3 undergoes a diffuse phase transition at T _m ?? 315 K. A specific heat anomaly that is characteristic of the phase transition has been revealed at T ?? 315 K in all the compositions under study.