Pb(Zr,Sn,Ti)O3反铁电陶瓷场诱相变性能的改进

为了获得场诱反铁电(AFE_t)—铁电(FE_Ｒ)相变临界电场E_{f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Ba ^2＋置换Pb^2＋,同时在四方反铁电相AFEt—三方铁电F EＲ相界附近调节Ti/Sn比,来控制FEＲ-AFEt,AFEt关键词： Pb(Zr Sn 3基反铁电陶瓷')" href="#">Ti)O3基反铁电陶瓷 场诱相变 场致应变 掺杂改性}     

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 .     

(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     

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     

(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}     

La诱导(Pb(1-3x/2)Lax)(Zr0.5Sn0.3Ti0.2)O3反铁电介电弛豫研究

采用标准电子陶瓷工艺制备了(Pb_(1-3x/2)La_x)(Zr_0.5Sn_0.3Ti_0.2)O₃(PLZST,0.00≤x≤0.18)反铁电陶瓷,利用X射线衍射、不同频率下弱场介电温谱、强场下的极化强度-电场(P-E)测试研究了材料相结构和电学性能.实验结果发现,随La含量x增大,室温下材料由铁电三方相(关键词： 反铁电陶瓷 介电频率色散 相变弥散 介电弛豫     

改性锆钛酸铅温度诱导相变的热释电性

测量结果显示,Pb_0.99Nb_0.02［(Zr_1-xSn_x)_1-yTi_y］_0.98O₃在温度诱导相变时伴随有正的和负的热释电电流峰.电流的方向与相变类型有如下关系：铁电相向反铁电或顺电相转变时形成正的电流峰,反铁电相向铁电或顺电相转变时形成负的电流峰.按照铁电相与反铁电和顺电相之间存在静电势差的观点,可以很好地解释热释电电流的方向与 关键词： 改性锆钛酸铅化合物 温度诱导相变 热释电性     

Pb(Zr,Sn,Ti)O3反铁电陶瓷的低温相变扩散与极化弛豫

用弱场介电温谱、热释电流谱、强场电滞回线和变温X射线衍射谱研究了微量La掺杂Pb(Zr,Sn,Ti)O₃(PZST)反铁电(AFEt)陶瓷在-100—180℃温区内的结构与电学特性.弱场介电温谱显示,AFEt陶瓷在低温段(-100—50℃)呈现介电频率弥散(0.1—100kHz)和扩散型相变的特征,而变温X射线衍射谱却表明材料在这一温区内保持四方相结构;低温下经强场作用后,AFEt被诱导为亚稳三方铁电态,介电频率弥散消失.基于多元复杂化合物的组分起伏理论,讨论了PZST AFEt陶瓷 关键词： Pb(Zr Sn 3反铁电陶瓷')" href="#">Ti)O₃反铁电陶瓷 反铁电弛豫 相变 变温X射线衍射     

等静压和温度诱导的PbLa(Zr,Sn,Ti)O3反铁电陶瓷相变和介电性能研究

研究了等静压和温度诱导掺镧La的Pb(Zr,Sn,Ti)O₃(PLZST)陶瓷材料的铁电反铁电相变、介电压力谱和介电温度谱,研究了温度对压致相变和介电压力谱的影响,结果发现温度使铁电反铁电相变压力降低,介电压力谱具有明显的扩散相变和频率弥散的特点;研究了等静压对介电温度谱的影响,结果表明等静压使铁电反铁电相变温度降低,反铁电顺电相变温度升高.这些现象有利于丰富和拓宽人们对温度和压力诱导的多组元弛豫型铁电体和弛豫型反铁电体扩散相变和弛豫行为的认识和理解. 关键词： 等静压和压致相变 铁电反铁电相变 介电压力谱 介电温度谱     

钛酸锶钡材料在外加电场作用下的拉曼光谱研究

采用传统的固相反应烧结方法制 备Ba_xSr_1-xTiO₃（0.40≤ x ≤0.70）陶瓷,借助于Raman散射光谱,研究了陶瓷样品在不同原位电场作用下Raman振动模式的变化,观察到居里温度附近显著的电场诱导的四方–立方相之间的转变. 结果表明A₁（TO₃）和E（TO₄）两种振动模式与晶体的结构存在密切的联系,这两种模式源于O-Ti-O沿晶格中c轴的方向和ab面内的振动. A₁（TO₃）/E（TO₄）之间Raman峰的相对强度比,随外加场强的增加明显升高,顺电相逐渐转变为铁电相,晶格的畸变越来越明显,其宏观性能上表现为介电常数的降低,可调率的增加. 同时对居里温度附近电场诱导的结构相变对顺电相下介电非线性的贡献进行了探讨. 关键词： 钛酸锶钡 Raman散射光谱 结构相变     

Dielectric properties and phase transitions of (Pb0.87La0.02Ba0.1)(Zr0.6Sn0.4−xTix)O3 ceramics with compositions near AFE/RFE phase boundary

The electrical properties and phase transition behavior of (Pb_0.87La_0.02Ba_0.1)(Zr_0.6Sn_0.4−xTi_x)O₃ solid solutions (PLBZST, 0.04≤x0.2) were investigated by the X-ray diffraction, permittivity, pyroelectric current, and P-E electric hysterisis loops. As the composition x increased from 0.04 to 0.2, the antiferroelectric ceramics (x≤0.07, AFE) with tetragonal phase changed to the ferroelectric relaxors (RFE, 0.09≤x). AFE ceramics showed a peculiar diffuse phase transition and dielectric relaxation at the low temperature (down to −100 °C) due to a frustration between AFE and FE state. With an increase in composition x, electrically field-induced AFE-FE switching field (E_AFE-FE) and AFE-paraelectric (PE) phase transition temperature (T_c) are depressed in the temperature (T)-Ti composition (x) phase diagram, a FE-AFE-PE triple phase point (T_tr) with the lowest transition temperature occurred at x=0.09. The pyroelectric currents under an application of various external electric field (E) were measured to identify a T-E phase diagram of the PLBZST compound.     

掺Ba对Bi系2212相超导电性的影响

研究了掺Ｂａ对Bi₂Sr_2-xBa_xCaCu₂O_y（０≤ｘ≤０．１５，０．３）单晶和多晶样品超导电性的影响，结果表明，有少量Ｂａ^２＋离子进入了超导相，且有固溶度极限．对于２２１２相单晶，ｃ轴参数和Ｔ_c均随Ｂａ含量增加而增加；对于慢冷多晶样品，掺Ｂａ可明显提高Ｔ_c；然而对于淬大多晶样品，Ｔ_c没有明显变化，用掺Ｂａ 关键词：     

Study of phase transitions and properties of tetragonal (Pb,La)(Zr,Ti)O3 ceramics—I: Phase diagram and β-phase

The phase diagram (T?x plot) of thermally depoled tetragonal PLZT materials has been investigated by means of X-ray diffraction, Capacitance and DSC measurements. Materials with a low La content show a classical Fe_t?PE_c transition. This transition has first or second order character, dependent on the Zr/Ti ratio.Materials with a medium and high La content show a diffuse transition from the cubic high temperature phase to a tetragonal, so called β phase. This β phase has no clear FE properties and a spontaneous transition to the FE_t phase on lowering the temperature only takes place for materials with a medium La content. For materials with a high La content a spontaneous β_t→ FE_t transition is not observed.     

Coexistence of ferroelectric and antiferroelectric microregions in the paraelectric phase of NH4H2PO4 (ADP)

Ammonium dihydrogen phosphate NH₄H₂PO₄ (ADP) is an antiferroelectric (AFE) compound belonging to the KDP-type family of hydrogen-bonded ferroelectrics. Recent ab initio results have shown that the optimization of the N–H–O bridges in ADP leads to the stabilization of the AFE state over a FE one. However, electron spin probe measurements have suggested that microregions of both phases may coexist above the critical antiferroelectric–paraelectric transition temperature. We have performed first principles studies of the energetics and relative stability of different AFE and FE defects embedded in a paraelectric (PE) matrix of ADP. Our analysis indicates that FE and AFE clusters are stable and may coexist in the PE phase, thus confirming the above suggestion.     

Electromechanical-induced antiferroelectricben ferroelectric phase transition in PbLa(Zr,Sn,Ti)O3 ceramic

Antiferroelectric—ferroelectric (AFE—FE) phase transition in ceramic Pb_0.97La_0.02(Zr_0.75Sn_0.136Ti_0.114)O₃ (PLZST) was studied by dielectric spectroscopy as functions of frequency (10²—10⁵ Hz) and pressure (0—500 MPa) under a DC electric field. The hydrostatic pressure-dependent remnant polarization and dielectric constant were measured. The results show that remnant polarization of the metastable rhombohedral ferroelectric PLZST poled ceramic decreases sharply and depoles completely at phase transition under hydrostatic pressure. The dielectric constant undergoes an abrupt jump twice during a load and unload cycle under an electric field. The two abrupt jumps correspond to two phase transitions, FE—AFE and AFE—FE.