布里渊散射决定0.67Pb(Mg_(1/3)Nb_(2/3))O_3-0.33PbTiO_3单晶的弹性、压电和介电常数(英文)

我们报道了用高分辨布里渊散射,确定0.67Pb(Mg1/3Nb2/3)O3-0.33PbTiO3单晶中的弹性、压电和介电常数.所有的实验数据都是在一块沿[001]方向的极化的单晶样品上获得的。我们实验中得到的这些常数的数值和以往超声共振技术获得的数值相似。我们还研究了压缩模和剪切模在(010)和(001)平面内的方向依赖性。TA1和TA2模式的强度对散射角度有很强列依赖性。在散射角度为45°~65°内,一个新的峰出现在~18 GHz附近。它可能与晶体中的微观不均匀性或者局域微结构相关。     

布里渊散射决定0.67Pb(Mg1/3Nb2/3)Ｏ3－0.33ＰbTiO3单晶的弹性、压电和介电常数

我们报道了用高分辨布里渊散射,确定0.67Pb(Mg1/3Nb2/3)Ｏ３－０．３３ＰbTiO3单晶中的弹性、压电和介电常数.所有的实验数据都是在一块沿［001］方向的极化的单晶样品上获得的。我们实验中得到的这些常数的数值和以往超声共振技术获得的数值相似。我们还研究了压缩模和剪切模在(010)和(001)平面内的方向依赖性。TA1和TA2模式的强度对散射角度有很强列依赖性。在散射角度为45°~65°内, 一个新的峰出现在~18 GHz附近。它可能与晶体中的微观不均匀性或者局域微结构相关。     

布里渊散射决定0．67Pb（Mg1／3Nb2／3）03-0．33PbTiO3单晶的弹性、压电和介电常数

我们报道了用高分辨布里渊散射,确定0．67Pb（Mg1／3Nb2、3）O2-0．33PbTiO2单晶中的弹性、压电和介电常数．所有的实验数据都是在一块沿[001]方向的极化的单晶样品上获得的。我们实验中得到的这些常数的数值和以往超声共振技术获得的数值相似。我们还研究了压缩模和剪切模在（010）和（001）平面内的方向依赖性。TA1和TA2模式的强度对散射角度有很强列依赖性。在散射角度为45°～65°内,一个新的峰出现在～18GHz附近。它可能与晶体中的微观不均匀性或者局域微结构相关。     

Polarized Micro-Raman Study of the Temperature-Induced Phase Transition In 0.67 Pb（Mg1/3Nb2/3）O3-0.33PbTiO3

Polarized Raman spectra of ferroelectric relaxor 0.67Pb（Mg1/3Nb2/3）O3-0.33PbTiO3 （0.67PMN-0.33PT） single crystal are systematically investigated in a wide temperature range from -196 to 600℃ by micro-Raman scattering technique. The results clearly reveal that there are two structural phase transitions in such composite ferroelectric relaxor： the rhombohedral-tetragonal （R- T） phase transition and the tetragonal-cubic （T- C） phase transition. The former occurs at about TR-T =34℃, corresponding to the vanishing of the soft A1 mode at 106cm^-1 recorded in the parallel polarization. The latter appears at about TT-C = 144℃, which can be verified with the vanishing of mode at 780cm^-1 measured in the crossed polarization.     

Kinetics of the phase transition in crystals PbIn1/2Nb1/2O3–PbMg1/3Nb2/3O3–x PbTiO3

The time dependences of the optical transmission, velocity of sound, and elastic constants at room temperature in a number of the [001]-oriented PbIn_1/2Nb_1/2O₃–PbMg_1/3Nb_2/3O_3–x PbTiO₃ single crystals with the compositions lying both far from the morphotropic phase boundary and in its vicinity have been investigated. The analysis of the data obtained has been carried out. It has been shown that, in all the studied crystals, phase transitions induced by an electric field occur in two stages: the first stage is an incubation period associated with a small increase in the polarization of a part of the sample being in the glass phase, and the second phase (after the incubation period τ) is a rapid increase in the polarization and the formation of a long-range order. It has been found that the time τ depends on how close is the temperature of measurements to the Vogel–Fulcher temperature T _f . The closer is the temperature of measurements to the Vogel–Fulcher temperature T _f , the weaker is the electric field required to be applied to the sample in order to induce a ferroelectric phase. It has been demonstrated that the phase state of the studied crystals is unstable, which manifests itself in a strong dependence of the incubation period τ on the time between the annealing of the sample and the beginning of the measurements. The stability of the phase state depends on the PbTiO₃ concentration: an increase in the concentration leads to a significant increase in the stability.     

弛豫型铁电单晶0.67Pb(Mg_(1/3)Nb_(2/3))O_3-0.33PbTiO_3的拉曼散射研究

本文采用拉曼散射技术在温度从374到-196℃的范围内,研究了弛豫型铁电单晶0.67Pb(Mg1/3Nb2/3)O3-0.33PbTiO3(PMNT)。观察了在不同温度下拉曼光谱的变化,经分析这些变化反映了该晶体经历了两个相变:第一个相变温度发生在120℃,从顺电立方相到铁电四方相的相变,780 cm-1处模式在VH偏振下的改变标志了这一相变;第二个相变温度发生在34℃,是从铁电四方相到铁电三方相的相变,软模的出现代表了这一相变。     

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.     

0.7Pb(Mg1/3 Nb2/3)O3-0.3PbTiO3单晶/环氧树脂1-3型复合材料的压电性能研究

模拟了0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3(PMN-0.3PT)单晶1-3型压电复合材料的性能与单品体积分数的关系,得出性能最优时压电相的体积分数为64%,在这一体积分数下,采用切割-填充法,并使用了不同类型的环氧树脂填充制备复合材料.系统地研究了聚合物相对复合材料性能的影响,研究表明,减小聚合物相的刚度系数c和密度ρ有利于提高复合材料的性能,且聚合物相与压电相的结合强度对性能的影响非常明显,制备的PMN-0.3 PT单晶1-3型复合材料的厚度伸缩机电耦合系数k1高达90.1%,压电系数d33大于1000 pC/N,机械品质因数Qm为10.39,声阻抗Z也大大降低,性能明显优于传统的Pb(Zrx,Ti1-x)O3(PZT)陶瓷及其1-3复合材料,在压电换能器和传感器中显示出广阔的前景.     

KTa_(1-x)Nb_xO_3单晶的相变软模(英文)

用Ｒａｍａｎ散射研究了四方钽铌酸钾单晶的顺电 铁电结构相变,在相变时发现和分析了一个凝聚的软晶格振动模ｖ５,它是产生于Ｏ２ Ｏ３键的对称弯曲振动。     

纳米尺寸下Pb1-xBaxTiO3的喇曼振动光谱及软模行为的研究

测量了Pb_1-xBa_xTiO₃(x=0,0.2,0.3)的喇曼光谱。实验结果表明该体系存在着明显的晶粒小尺寸效应。 关键词：     

Polarized Raman mapping study of the microheterogeneity in 0.67PbMg1/3 Nb2/3O3‐0.33PbTiO3 single crystal

Polarized micro‐Raman spectroscopy was carried out on the (001) face of a 0.67PbMg_1/3Nb_2/3O₃‐33%PbTiO₃ (PMN‐33%PT) single crystal. The Raman images revealed the spatial variations of the intensity of the Raman bands, suggesting that the structure in the PMN‐33%PT single crystal varied from one micro‐area to another. When changing the polarization direction of the incident light with respect to the selected crystalline axes, the intensities of the Raman modes varied periodically. According to the Raman selection rules (RSRs), the angular dependences of the Raman modes indicated that the PMN‐33%PT single crystal is in the monoclinic phase. Furthermore, the color patterns in the Raman images were associated with the coexistence of the M_A‐ and M_C‐type monoclinic phases in the PMN‐33%PT single crystal. Our results provide useful information for understanding the microheterogeneity of the relaxor PMN‐xPT single crystals with compositions near the morphotropic phase boundary region. Copyright © 2010 John Wiley & Sons, Ltd.     

Optical and acoustic properties of 33PbIn1/2Nb1/2O3-35PbMg1/3Nb2/3O3-32PbTiO3 single crystals in an electric field

The influence of different conditions of applying a dc electric field (0 < E < 4 kV/cm) on the behavior of optical transmission and on the acoustic parameters (sound velocity and attenuation) in the [001]- and [011]-oriented single crystals 33Pb(In_1/2Nb_1/2)O₃-35PbMg_1/3Nb_2/3O₃-32PbTiO₃ existing near the morphotropic phase boundary has been investigated. It has been found that the optical transmission, sound velocity, and attenuation sharply change near the phase transition in a narrow range of electric fields for any method of their applying. In the field applied along [001], the change in the sound velocity due to the phase transition is 1.5 times greater than that in the field applied along [011]. This is caused by a larger contribution of the piezoelectric effect to the elastic modulus determining the sound velocity along [001] as compared to [011]. It has been shown that the number, symmetry, and stability of the phases formed in the field depend on the conditions of applying the field.     

A polarized micro-Raman study of a 0.65PbMg1/3Nb2/303-0.35PbTi03 single crystal

Polarized micro-Raman spectra of a 0.65PbMg_1/3Nb_2/3O₃-0.35PbTiO₃ （0.65PMN-0.35PT） single crystal poled in the [001] direction are obtained in a wide frequency range （50-2000 cm 1） at different temperatures.The best fit to the Raman spectrum at 77 K is achieved using 17 Lorenzians to convolute into it,and this is proved to be a reasonable fit.According to the group theory and selection rules of overtone and combinational modes,apart from the seven Raman modes that are from first-order Raman scattering,the remaining ones are attributed to being from second-order Raman scattering.A comparison between the experimental results and theoretical predictions shows that they are in satisfactory agreement with each other.Our results indicate that at 77 K the sample belongs to the rhombohedral symmetry with the C 5 3v （R3m） space group （Z=1）.In our study,on heating,the 0.65PMN-0.35PT single crystal undergoes a rhombohedral → tetragonal → cubic phase transition sequence.The two phase transitions occur at 340 and 440 K,which correspond to the disappearance of the soft mode near 106 cm 1 recorded in VV polarization and the vanishing of the band around 780 cm 1 in VH polarization,respectively.     

弛豫铁电单晶0.93Pb(Zn1/3Nb2/3)O3-0.07PbTiO3的电光性能研究

以波长为632.8 nm的He-Ne激光作为光源,研究了三方相弛豫铁电单晶0.93Pb(Zn1/3Nb2/3)O3-0.07PbTiO3在室温下的折射率和线性电光性质.通过测量晶体的布儒斯特角,确定了单晶的两个主轴折射率:no=2.466,ne=2.488.利用改进的马赫-泽德尔干涉法测量了单晶的线性电光系数:r33=71 pm/V,r13=4 pm/V.计算得到有效电光系数rc=67 pm/V及半波电压Vπ=610 V.单晶优异的电光性能使其在激光调制与偏转领域有着巨大的应用潜力.     

Elastic,dielectric, and piezoelectric characterization of 0.92Pb(Zn1/3Nb2/3)O3-0.08PbTiO3 single crystal by Brillouin scattering

In this paper,a complete set of elastic,piezoelectric,and dielectric constants of high-quality tetragonal poled0.92Pb(Zn_(1/3)Nb_(2/3))O_3-0.08PbTiO_3 single crystal grown by the modified flux method is determined using high-resolution Brillouin scattering.A comparison is made between the results obtained by a hybrid method combining ultrasonic and resonant techniques and the results obtained by the Brillouin scattering.The elastic,piezoelectric,and dielectric constants obtained by the two methods are similar.The Brillouin spectrum consists of one longitudinal and two transverse acoustic phonon modes,and the variations of the Brillouin shifts,the full widths at half maximum,and the scattering intensities of these modes with scattering angle 9 are investigated.In particular,the transverse acoustic phonon mode at the lowfrequency becomes markedly soft from 28.2 GHz to 18.4 GHz and broadens gradually with the increase of θ,while its intensity decreases gradually as compared with that of the original one.The possible origins of the results are discussed.     

Effect of electric field on the smeared phase transition in crystals PbIn1/2Nb1/2O3-28PbTiO3 and PbIn1/2Nb1/2O3-37PbTiO3

The effect of a direct-current electric field (0 < E < 3 kV/cm) on the smearing of the phase transition and the Curie-Weiss exponent (γ) for two PbIn_1/2Nb_1/2O₃-28PbTiO₃ and PbIn_1/2Nb_1/2O₃-37PbTiO₃ crystals lying at different distances from the morphotropic phase boundary has been investigated. The universal Curie-Weiss law has been used to approximate the temperature dependences of the dielectric permittivity. It has been shown that the more remote is the crystal from the morphotropic phase boundary, the larger is the exponent γ and, consequently, the more smeared is the phase transition (in the zero field, γ = 1.67 and 1.49 for PbIn_1/2Nb_1/2O₃-28PbTiO₃ and PbIn_1/2Nb_1/2O₃-37PbTiO₃, respectively). It has been found that a weak electric field (no greater than 2–3 kV/cm) in the case of the more smeared phase transition almost does not affect the Curie-Weiss exponent, whereas for the PbIn_1/2Nb_1/2O₃-37PbTiO₃ crystal, this exponent decreases with increasing electric field strength and approaches γ = 1, which is characteristic of the conventional ferroelectric.