(PbBa)(Zr,Sn,Ti)O_3反铁电/弛豫型铁电相界陶瓷的相变与介电、热释电性质

通过对(Pb087Ba01La002)(Zr06TixSn04-x)O3(004≤x≤020)固溶体的介电和偏压热释电性质的研究发现,当Ti含量004≤x≤007时,材料是反铁电四方相,而当009≤x≤020时,材料向弛豫型铁电体转化.在温度Ti含量相图中,x=009附近形成了反铁电铁电顺电三相共存点(Ttr).该点的相变温度最底;对于004≤x≤007的反铁电四方相,低温下呈现介电弛豫特征,并可被外电场诱导为亚稳铁电态,温度升高时,亚稳铁电→反铁电相变,反铁电→顺电相变引起两个热释电流峰,偏置电场下峰位和峰强均发生移动,在温度电场相图中也形成了铁电反铁电顺电三相点.从复杂化合物纳米相分离的观点和晶格动力学出发,讨论了相变与电学性能随Ti含量(x)和外电场(E)变化的物理机理. 关键词： 反铁电/弛豫型铁电相界 介电性能 偏压热释电性质 铁电-反铁电-顺电三相点     

钙钛矿型氧离子导体KNb1-xMgxO3-δ的制备和表征

在高温高压（4.0GPa，870℃）下合成了具有正交钙钛矿结构的KNb_1-xMg_x O_3-δ（x=0.0—0.3）系列固体电解质，并系统地研究了Mg掺杂对其结构相变和导电性的影响.变温拉曼谱和DTA测量结果表明，随着温度的升高，KNb_{1-xMgxO3-δ发生了结构相变，由铁电正交、四方相转变为顺 电立方相.由于Mg掺杂削弱了B位离子对自发极化的贡献以及A位离子与BO关键词： 钙钛矿 离子电导 1-xMgxO3-δ')" href="#">KNb1-xMgxO3-δ 高温高压 铁电相变}     

LiTaO3的高温拉曼光谱研究

利用显微共聚焦拉曼光谱技术研究了LiTaO3晶体在298～948K温度范围内的拉曼光谱,通过对其高波数拉曼峰的分析,研究了LiTaO3的相变机制。研究发现,除466.7cm-1峰外,LiTaO3的其余拉曼峰随着温度的升高向低波数方向明显频移;所有拉曼峰的半高宽随着温度的升高逐渐增加,同时拉曼峰的强度逐渐减弱;在933K附近,LiTaO3的三个拉曼峰的消失,表明LiTaO3发生了从低温铁电相到高温顺电相的相变;与此同时,在该温度附近,359.5,385.0以及466.7cm-1峰的半高宽存在超线性增加。研究结果表明,LiTaO3从低温铁电相到高温顺电相的相变是一种混合型相变,其相变过程可逆。     

PbZr_(0.52)Ti_(0.48)O_3陶瓷的高压拉曼光谱研究

作为重要的铁电陶瓷材料之一,PbZr0.52Ti0.48O3(PZT)陶瓷因其广泛的工业应用而成为研究的焦点。通过水溶的溶胶-凝胶法,合成了PbZr0.52Ti0.48O3陶瓷片。通过拉曼光谱测试技术结合高压实验,系统地研究了PZT(MPB-PZT:PbZr0.52Ti0.48O3)陶瓷在不同压力下的拉曼光谱。拉曼光谱实验结果分析表明,在0~25GPa的压力范围内,随着静水压力的增加,在压力为2.61GPa时,PZT陶瓷发生了从三方-四方混合相到四方-立方混合相的结构相变,随着压力继续增大到8.5GPa,PZT陶瓷完全相变为顺电立方相。同时,对PZT陶瓷片的介电常数进行了测试,确定PZT陶瓷片的居里温度为395℃。     

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。     

La调节Pb(Zr,Sn,Ti)O_3反铁电陶瓷的相变与电学性质

利用X射线衍射、弱场介电温度谱、强场极化强度研究了不同La含量(Pb1-xLa2x3)(Zr06Sn03Ti01)O3(000≤x≤012)(PLZSnT)陶瓷的相变与电学特性.实验发现,随La含量增大,室温下材料由铁电三方相(x=000)转变为反铁电四方相(003≤x≤009)和立方相(x=012).介电测试表明,La含量增大,反铁电→顺电相变温度降低,峰值介电常量减小.在x=006的PLZSnT三元相图中,反铁电四方相区扩大到Ti含量约为18at%,该系统反铁电陶瓷具有“窄、斜”型双电滞回线和“三电滞回线”;在高Zr、高Sn区,反铁电→顺电相变呈现弥散相变和介电频率色散特征,即反铁电极化弛豫现象.从ABO3钙钛矿结构的容忍因子(t)和反铁电相的结构特征出发,讨论了La对Pb(Zr,Sn,Ti)O3相变与电学性质的影响机理 关键词： 场诱相变 弛豫型反铁电体 介电性能 La调节Pb(Zr Sn Ti)O3     

相界附近Pb(Zn1/3Nb2/3)O3-PbZrO3-PbTiO3固溶体的弛豫相变研究

利用常规电子陶瓷工艺在相界附近合成得到纯钙钛矿相的Pb(Zn1/3Nb2/3)O3PbZrO3PbTiO3(PZNPZT)三元系固溶体,其相界位于Zr/Ti比37/33处.在实验中发现和证实了相界附近PZNPZT三元系固溶体存在铁电弛豫顺电相变.在极化后Zr/Ti比为37/33及39/31PZNPZT样品的介电温度谱观测到菱方四方相相变,认为PZNPZT固溶体相界是向富Zr区弯曲. 关键词：     

Pb(Zr,Sn,Ti)O_3反铁电陶瓷场诱相变性能的改进

为了获得场诱反铁电 (AFEt)—铁电 (FER)相变临界电场Ef 小、电滞ΔE小、场致应变x适当的反铁电陶瓷 ,对Pb(Zr ,Sn ,Ti)O3 采用Ba2 置换Pb2 ,同时在四方反铁电相AFEt—三方铁电FER 相界附近调节Ti/Sn比 ,来控制FER AFEt,AFEt 顺电相 (FEC)之间的相变温度TFA,TC,最终实现了对场诱相变参量 (Ef,ΔE)和反铁电工作温区 (ΔT =TC-TFA)的优化与调节 .获得了ΔE =0 85kV/mm ,Ef=1 6kV/mm ,x =0 1% - 0 2 %可用作开关致动器的新型反铁电陶瓷 .借助于X射线衍射、介电温谱、去极化电流谱、电滞回线等手段得到了这一系统AFEt/FER相界附近的温度 Ti含量相图 .     

(Pb0.97La0.02)(Zr0.65Sn0.35-xTi x)O3反铁电陶瓷的热膨胀性质

在-100—200℃温度范围内，测量了(Pb_0.97La_0.02)(Zr_{0.65< /sub>Sn0.35-xTix)O3(PZST，0.1≤x≤0.14)反铁电陶 瓷的热膨胀性质.实验结果表明，组分在0.1 ≤x≤0.12的试样室温下为反铁电(AFEt)四方相，热膨胀系数(α)在低温段发生 “弯曲” ，而变温x射线衍射谱(XRD)显示材料保持四方相结构；当Ti含量在0.125≤x≤0.14时，室温 下是铁电三方相(FER)，温度升高时FER→AFEt相变体 积收缩，AFEt→立方顺电(PE c)相变体积增大；变温XRD谱证明了材料相结构随温度的转变过程.用多元复杂 化合物存在 纳米线度组分非均匀的观点解释了热膨胀性质随Ti含量演化的物理机理，并得到了该系统的 温度-Ti(x)含量相图. 关键词： 热膨胀性质 铁电/反铁电相界 反铁电陶瓷 PZST}     

铁掺杂四方、三方两相共存PZN-PZT陶瓷的Raman散射分析

Raman散射常用于研究温度变化时铁电体的各种相变,如铁电-顺电相变等,但是,利用Raman散射研究掺杂诱导的相变并不常见。本文采用Raman散射研究了铁掺杂Pb(Zn1/3Nb2/3)0.2(Zr0.5Ti0.5)0.8O3(PZN-PZT)铁电陶瓷中三方-四方共存现象。通过分析四方相E(3TO)和A1(3TO)模式与三方相Rl模式,确定了铁掺杂对PZN-PZT陶瓷中三方-四方共存结构的影响。这一结果,得到了XRD相分析的验证。因此,通过对Raman散射中三方-四方振动模式的分析,可以表征掺杂诱导的PZT基陶瓷中三方-四方相结构变化趋势。     

Phase transformation in (0.90−x)Pb(Mg1/3Nb2/3)O3-xPbTiO3-0.10PbZrO3 piezoelectric ceramic: X-ray diffraction and Raman investigation

Piezoelectric ceramics with compositions of (0.90−x)Pb(Mg_1/3Nb_2/3)O₃-xPbTiO₃-0.10PbZrO₃, x=0.28, 0.31, 0.34, 0.37, 0.40 and 0.43, were prepared using the conventional columbite precursor method, and their structural phase transformation and piezoelectric behaviors near the morphotropic phase boundary (MPB) have been systematically investigated as a function of PbTiO₃ content. X-ray diffraction (XRD) results demonstrate that the structure of the ceramics experiences a gradual transition process from rhombohedral phase to tetragonal phase with the increasing of PbTiO₃ content, and that compositions with x=0.34-0.40 lie in the MPB region of this ternary system. A Raman spectra investigation of the ceramic samples testified to the transformation process of rhombohedral phase to tetragonal phase by comparing the relative intensities of tetragonal E(2TO₁) mode and rhombohedral phase R_h mode. The structure information was also correlated to the parabola change of the piezoelectric constant; the maximum piezoelectric constants were obtained near the MPB region.     

A comparative Raman study of 0.65(PbMg<Subscript>1/3</Subscript>Nb<Subscript>2/3</Subscript>O<Subscript>3</Subscript>) -0.35(PbTiO<Subscript>3</Subscript>) single crystal and thin film

We report a comparative Raman study of 0.65(PbMg_1/3Nb_2/3O₃)-0.35(PbTiO₃) (PMN-0.35PT) single crystal and thin film. Raman spectra investigation indicates a change in bulk from the high temperature cubic to the tetragonal phase and then to the low temperature Mc monoclinic phase. The transition temperatures are in good agreement with the ones previously observed by dielectric measurements on the same sample. In contrast, we observe no phase transition to the monoclinic phase in the PMN-0.35PT 4000 Å thick film and only a cubic to tetragonal diffuse transition has been determined at high temperature. The enhanced stability of the tetragonal phase and the absence of low temperature monoclinic phase have been attributed to the in plane strain.     

正磷酸盐晶体Ba3(PO4)2和Sr3(PO4)2高温拉曼光谱研究

测量了碱土金属正磷酸盐Ba₃(PO₄)₂和Sr₃(PO₄)₂常温及高温拉曼光谱, 对拉曼振动模式进行指认, 并分析了晶体拉曼振动光谱及晶体结构在高温下的变化. 在温度升高的过程中, 拉曼振动频率向低频移动且振动峰宽度展宽, 晶体中的P-O平均键长随温度升高而变长, 但O-P-O的键角并未发生变化. 晶体在900 ℃以下无结构相变发生. 关键词： 3(PO₄)₂和Sr₃(PO₄)₂')" href="#">Ba₃(PO₄)₂和Sr₃(PO₄)₂ 高温拉曼光谱 振动模式 高温结构     

A polarized micro-Raman study of a 0.65PbMg1/3Nb2/3O3 - 0.35PbTiO3 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_3v⁵ (R3m) space group (Z=1). In our study, on heating, the 0.65PMN-0.35PT single crystal undergoes a rhombohedral to tetragonal to 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.     

Raman spectra of YBa2Cu3Ox (x=6−7)

Raman spectra of polycrystalline YBa₂Cu₃O_x with various oxygen content x were recorded at 30 K. The intensity of the Cu-O stretching mode at 505 cm^-1 depends on the oxygen content significantly. This peak becomes weak as the oxygen content decreases and finally disappears at x=6.05. The last result disagrees with previous Raman studies on the tetragonal phase. Other spectral changes, disappearance of the 115 cm^-1 peak and shifts of some peaks, are observed at the oxygen content of ≈6.8.     

Raman study of the phase separation in ZrO2-12 mol% CeO2 ceramic

We present Raman spectra of the ZrO₂-12 mol% CeO₂ ceramic heat- treated at 1000°C, 1200 °C and 1420 °C in the flowing mixture gas of H₂+Ar. Raman spectra reveal the tetragonal to monoclinic phase transition and three Raman bands are observed at 279 cm^-1, 410 cm^-1 and 456 cm^-1 at temperatures above 1200 °C; it turned out that these Raman bands are assigned to neither of the monoclinic phase nor the tetragonal phase. It is suggested that the starting ceramic undergoes phase separation in the heat-treatments in the mixture gas of H₂+Ar; the phase separation probably takes place as a result of the valence change of Ce during the heat-treatments, which leads to destabilization of the original tetragonal phase.     

低温拉曼光谱研究钛酸铋尺寸驱动的相变

本文对粒径为25~75 nm的钛酸铋纳米晶在-190℃温度的低温拉曼光谱进行了研究,结果表明,在钛酸铋纳米晶中,除了存在已知的尺寸驱动的铁电正交-顺电四方的结构相变外,还存在尺寸驱动的细微的单斜-正交的结构相变。     

紫外拉曼光谱研究钇掺杂的氧化锆体系表面相变

本文用紫外拉曼 ,近可见拉曼光谱和XRD检测了不同焙烧温度下Y2 O3-ZrO2 的相变过程。紫外拉曼光谱对样品表面相变极其灵敏 ,而近可见拉曼光谱和XRD提供的主要是体相和表面的混合信息。在紫外拉曼谱图中 ,只观察到单斜相的谱峰 ,没有明显的四方晶相的信号 ,这表明样品的表面主要是单斜晶相。然而 ,XRD和近可见拉曼光谱的结果显示Y2 O3-ZrO2 体相是四方晶相。焙烧温度超过 40 0°时 ,紫外拉曼 ,近可见拉曼和XRD晶之间明显不同的结果表明Y2 O3-ZrO2 在表面区四方相很易转变为单斜相 ,体相中的四方相由于钇的添加而稳定存在。根据紫外拉曼和XRD结果 ,当升高温度时 ,在样品的表面形成一单斜相层 ,体相钇稳定的四方相 ,且由于Y2 O3的存在抑制了单斜相进一步向体相发展。