强电场作用下反铁电锆钛酸铅的介电行为研究

采用电滞回线方法和偏置直流电场中叠加小交变电场方法研究了锆钛酸铅反铁电陶瓷材料在强电场作用下的介电行为.测量结果显示，锆钛酸铅反铁电材料的介电常数随外加电场强度呈非线性变化，在反铁电 铁电转变的电场区间形成介电峰.表征极化强度随电场强度变化率的微分介电常数εd峰值出现在反铁电 铁电转换电场强度处，最高达到41000.随着偏置电场增加反铁电向铁电体转变过程中，小信号介电常数εc减小；在电场降低铁电回复成反铁电过程中，小信号介电常数εc增大，小信号介电常数εc峰先于微分介电常数εd峰出现.根据电场作用下反铁电 关键词： 锆钛酸铅反铁电陶瓷 介电行为 强电场条件     

静水压下锆锡钛酸铅铁电陶瓷相变和介电性能研究

研究了铌掺杂锆锡钛酸铅铁电陶瓷Pb_0.99Nb_0.02[(Zr_0.90Sn_0.10)_0.96Ti_0.04]_0.98O₃(PZST 90/10-4-2Nb)在静水压(0-300 MPa)下的电荷释放量和介电性能. 对压力诱导的低温铁电三方(F_R(LT))→反铁电正交(A_O)相变进行了研究. PZST 90/10-4-2Nb铁电陶瓷分为未极化、极化和压力去极化三种. 极化PZST 90/10-4-2Nb陶瓷F_R(LT)→A_O相变过程中,电荷释放量为29.3 μC/cm²,相变压力为140 MPa. 介电性能表明:极化PZST 90/10-4-2Nb陶瓷相变压力为136 MPa,而未极化陶瓷相变压力为104 MPa,压力去极化陶瓷未表现出明显的相变特征. 关键词： 静水压 铁电陶瓷 相变 介电     

冲击波作用下Pb(Zr_(0.95)Ti_(0.05))O_3铁电陶瓷去极化后电阻率动态特性

在冲击波压力作用下,极化Pb(Zr_(0.95)Ti_(0.05))O_3(PZT95/5)铁电陶瓷会发生铁电-反铁电相变失去极化,由于冲击波压力高、作用时间短,伴随材料去极化相变出现的瞬态电导特性难以准确测试.本文建立了新的实验方法,采用脉冲电容器作为冲击波加载铁电陶瓷脉冲电源的输出负载,在冲击波压力约3.5 GPa的实验中直接测得铁电陶瓷的漏电流,计算得到PZT95/5铁电陶瓷去极化后的电阻率,变化范围为2.2×10~4—3.5×10~4?·cm;在实验数据的基础上,建立了动态电阻模型,对冲击波传播过程中PZT95/5铁电陶瓷去极化后的电阻率进行了分析,初步揭示了冲击波作用下PZT95/5铁电陶瓷去极化后电阻率的动态特性.     

外加电场对铁电薄膜相变的影响

采用热力学非线性理论,研究了外加电场对立方基底Pb(Zr_0.3Ti_0.7)O₃(PZT)铁电薄膜相变的影响.通过数值计算,得到了"失配应变-外加电场"相图,及外加电场与极化强度的关系.当外加电场达到186 kV/cm时,能使生长在SrTiO₃ 基底上PZT铁电薄膜从单斜r相转变为c相.在实验上,采用扫描探针显微镜通过对PZT薄膜施加不同的极化电场来研究了它的电畴翻转.从得到的压电响应相图可以看出,绝大多数的电畴是清晰可 关键词： 铁电薄膜 相变 扫描探针显微镜 失配应变     

PbLa(Zr,Sn,Ti)O_3反铁电陶瓷的静电场能存储特性北大核心CSCD

为了研究微量掺镧的反铁电陶瓷锆锡钛酸铅(PbLa(Zr,Sn,Ti)O_3,PLZST)的静态存储电场能量的特性,采用传统的氧化物固态反应的陶瓷制备工艺,制备了4个锆锡比不同的PLZST陶瓷样品,样品组分均位于PLZST相图中铁电-反铁电相界附近。通过等静压压致放电的实验方法研究了PLZST陶瓷放电特性。结果表明,经过充分极化的PLZST处于亚稳态的铁电相,在压力作用下,PLZST发生铁电反铁电相变,把在直流电场下极化时储存于PLZST陶瓷的静电场能量瞬间释放出来,从而得到极高功率的电脉冲。最终,样品完全退极化,最大放电电流密度达到5.0nA/cm^2,样品的静电场储能密度最高可达9.45J/cm^3,因此PLZST陶瓷是爆电换能电源的理想材料。     

PbLa(Zr,Sn,Ti)O_3反铁电陶瓷的静电场能存储特性

为了研究微量掺镧的反铁电陶瓷锆锡钛酸铅(PbLa(Zr,Sn,Ti)O_3,PLZST)的静态存储电场能量的特性,采用传统的氧化物固态反应的陶瓷制备工艺,制备了4个锆锡比不同的PLZST陶瓷样品,样品组分均位于PLZST相图中铁电-反铁电相界附近。通过等静压压致放电的实验方法研究了PLZST陶瓷放电特性。结果表明,经过充分极化的PLZST处于亚稳态的铁电相,在压力作用下,PLZST发生铁电反铁电相变,把在直流电场下极化时储存于PLZST陶瓷的静电场能量瞬间释放出来,从而得到极高功率的电脉冲。最终,样品完全退极化,最大放电电流密度达到5.0nA/cm~2,样品的静电场储能密度最高可达9.45J/cm~3,因此PLZST陶瓷是爆电换能电源的理想材料。     

负脉冲激励下PLZST电子发射特征及发射机理研究

采用固态烧结工艺制备了位于反铁电/铁电相界附近的掺镧锆锡钛酸铅（PLZST）反铁电陶瓷样品.采用该样品作为阴极材料,研究了其在负脉冲激励电场下的电子发射行为.负脉冲激励下,0.5 mm厚PLZST反铁电陶瓷圆片发射阈值电压为500 V;当激励电压为500 V,抽取电压为3.5 kV时,得到690 A发射电流.结果表明,PLZST反铁电陶瓷发射阈值电压低,发射电流大,即使激励电场低于陶瓷的正向开关电场,仍能得到强发射电流.最后,讨论了PLZST反铁电陶瓷在负脉冲激励下电子发射内在机制. 关键词： 反铁电材料 铁电阴极 电子发射     

PbLa(Zr,Sn,Ti)O_3反铁电陶瓷在脉冲电场下的极化与相变行为

在实际应用中,反铁电陶瓷常处于快速变化的脉冲电场下,而传统电滞回线测量时所施加的电场变化速率较慢,并不能真实反映反铁电陶瓷实际应用时的极化和相变行为.本研究建立了反铁电陶瓷脉冲电滞回线测试平台,研究了Pb_(0.94)La_(0.04)[(Zr_(0.52)Sn_(0.48))_(0.84)Ti_(0.16)]O_3反铁电陶瓷在微秒级脉冲电场下的极化和相变行为.研究结果表明,反铁电陶瓷在微秒级脉冲电场下可以发生相变,但其极化强度降低,正向相变电场变高,反向相变电场变低,从而导致其储能特性发生了显著的变化.因此,低频电滞回线并不能真实反映反铁电陶瓷在脉冲电场下的性能,脉冲电滞回线对其应用具有更重要的参考价值.     

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 .     

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     

Large pyroelectric response in (Pb0.87La0.02Ba0.1)(Zr0.7Sn0.3−x Ti x )O3 antiferroelectric ceramics under DC bias field

(Pb_0.87La_0.02Ba_0.1)(Zr_0.7Sn_0.3−x Ti _x )O₃ (PLBZST, 0.06≤x≤0.09) antiferroelectric ceramics were fabricated by conventional solid state reaction process, and their ferroelectric, dielectric, and pyroelectric properties were systemically investigated. PLBZST with different Ti content were all confirmed to be in an antiferroelectric phase at T=50°C, which is close to the lowest phase transition temperature. Compared with conventional FE ceramics, PLBZST antiferroelectric ceramics exhibited higher electric field induced pyroelectric coefficient (p). As the content of Ti increased from 0.06 to 0.09, the pyroelectric coefficient increased from 1000 to 6500 μC/m²K under a 500 V/mm DC bias field. The maximum pyroelectric coefficient of 8400 μC/m²K was obtained at x=0.09 when an 850 V/mm DC bias field was applied, which is far larger than that of conventional phase transition pyroelectric materials. Large pyroelectric response is beneficial for the development of infrared detectors and thermal imaging sensors.     

Phase transition and linear thermal expansion of (Pb1− x Ba x )ZrO3 ceramics

(Pb_{1? x} Ba _x )ZrO₃ ceramics for the composition range 0?≤?x?≤?0.30 were prepared by the mixed oxide solid state reaction method. Phase transition was studied by dielectric and dilatometric measurements. The ferroelectric to paraelectric phase transition temperature was progressively shifted to a lower temperature by replacing lead with barium. The x?=?0.20 sample showed the maximum dielectric constant of 16,300 at the transition temperature. For compositions 0?≤?x?≤?0.075, the antiferroelectric to ferroelectric phase transition exhibited a large linear thermal expansion. However, the antiferroelectric to ferroelectric phase transition did not exist for 0.10?≤?x?≤?0.30 samples. A phase diagram for PBZ ceramics prepared by the conventional mixed oxide method was also present.     

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     

Investigation of ferroelectric phase transition for modified barium titanate in multilayer ceramic capacitors by in situ Raman scattering and dielectric measurement

The ferroelectric phase behaviors of modified BaTiO₃ in X7R multilayer ceramic capacitors (MLCCs) were investigated by dielectric measurements and in situ Raman scattering. The in situ thermo-Raman scattering shows that because of a residual stress existing in the MLCCs, the tetragonal to cubic phase transition for modified BaTiO₃ in MLCCs takes place over a wide temperature range of 373 K to 473 K, suggesting a diffuse-like characteristic which can be well explained by a modified phenomenological thermodynamic model, while the dielectric measurement indicates that the tetragonal to cubic transition occurs at 393 K. A disagreement exists between the two experimental results. Furthermore, a dc field-induced paraelectric to ferroelectric transition was identified by the two measurement techniques, but their phase-transition mechanisms are different. The dielectric measurement reveals the polar-micro-region to macro-domain transformation in the shell part of the core–shell structure while the in situ Raman scattering shows the cubic to tetragonal transition under a dc bias field. PACS 74.20.De; 77.22.Ch; 77.84.Dy; 77.80.Bh; 78.30.-j     

Bias field effects on the dielectric properties of 0.67Pb(Mg1/3Nb2/3)O3-0.33PbTiO3 single crystals with different orientations

The domain states and phase transitions in 0.67Pb(Mg_1/3Nb_2/3)O₃-0.33PbTiO₃ single crystals were investigated by studying their relative permittivity under various dc bias at constant heating and cooling rates. The orientation dependence of the bias field effect was revealed by examining the temperature dependence of relative permittivity as a function of crystal orientation (the 〈111〉, 〈011〉 and 〈001〉 directions) and dc bias field. The crystals basically have a macrodomain rhombohedral ferroelectric state in the ferroelectric phase under zero dc bias. External bias field could modulate the domain state and induce a stable macrodomain state in the crystals. Also, it is proposed that the dc bias applied along the 〈001〉 or 〈011〉 direction could induce a tetragonal ferroelectric phase or an orthorhombic ferroelectric phase, respectively, in an intermediate temperature range.     

Magnetoelectric coupling in antiferroelectric and magnetic laminate composites

We researched the properties of magnetoelectric composites between antiferroelectric Pb_0.94La_0.04(Zr_0.55Sn_0.3Ti_0.15)O₃ and magnetic Terfenol-D. The magnetic field enhances the electric field-induced strain and polarization of the composite. The magnetic moment induced by the electric field increases at the electromechanical resonance frequency because the antiferroelectric ceramics exhibit ferroelectric behaviors under a high electric field. The induced magnetic moment increases with decreasing thickness ratio and shows a hysteresis loop with the bias magnetic field. Due to the antiferroelectric characteristics, it also shows a hysteresis loop with the bias electric field, which could be used in the magnetic switch controlled by electricity.     

等静压诱导的PbLa(Zr,Sn,Ti)O3陶瓷铁电-反铁电相变性能研究

 研究了等静压诱导掺镧La的Pb(Zr,Sn ,Ti)O₃（PLZST）陶瓷材料的铁电-反铁电相变和介电压谱,结果发现介电压谱具有明显的扩散相变和频率弥散的特点,这一现象有利于拓宽人们对压力诱导的多组元弛豫型铁电体的扩散相变行为的认识和理解。     

Control of the temperature hysteresis and diffuse dielectric anomaly in the temperature range of the ferroelectric-antiferroelectric phase transition in PbZr1 − x TixO3 (0.03 ≤ x ≤ 0.05) ceramics

The magnitudes of the temperature hysteresis and diffuse dielectric anomaly corresponding to the transition from the antiferroelectric phase to the ferroelectric phase in PbZr_{1 ? x} Ti_xO₃ (0.03 ≤ x ≤ 0.05) ceramics can be reversibly changed by varying the temperatures of heating and cooling in the course of thermocycling. The results obtained indicate that the antiferroelectric-ferroelectric transition in the PbZr_{1 ? x} Ti_xO₃ ceramics materials is a smeared first-order phase transition.