铌镁酸铅弛豫型铁电陶瓷的介电老化行为研究

通过典型弛豫型铁电陶瓷铌镁酸铅介电老化行为的研究,发现高温区的Debye型弛豫过程与介电老化现象存在有机联系,指出复合钙钛矿弛豫型铁电体的结构缺陷特征对其介电老化起着重要作用.介电极化行为与老化行为对比分析和恒温经时老化研究表明,结构缺陷上的局域化电子和空穴对铁电微畴畴壁\"钉扎\"效应产生弛豫型铁电体介电老化行为的快过程.     

铌锌酸铅基铁电陶瓷的介电弥散行为

通过对（０．９－ｘ）Ｐｂ（Ｚｎ１／３Ｎｂ２／３）Ｏ３－）．１ＢａＴｉＯ３－ｘＰｂＴｉＯ３（ｘ＝０．００,０．０５,０．１０,０．１５）系列铁电陶瓷射频（２０－１ＧＨｚ）复介电常数ε（ε＝ε＋ｉε）的测试,观察到春介电弥散行为在１０ＭＨｚ以下随ＰｂＴｉＯ３含量的增加而减弱;在１０ＭＨｚ以上却同强烈的介电弥散,伴有强烈的介电损耗峰,并且介电损耗峰随ＰｂＴｉＯ３含量的增加而向高频移动。结合其介电温度谱与     

Pb(Zn1/3Nb2/3)O3基复相陶瓷的室温介电老化行为

研究了Ｐｂ（Ｚｎ１／３Ｎｂ２／３）Ｏ３基复相陶瓷的室温介电老化行为与材料烧成制度的关系,性机和介电常数与老化时间的对数值成线性关系,随烧成温度提高和保温时间延长,老化速率增大,老化速率对频率的依存性增加。低温短时间烧结的复相陶瓷的介电老化行为类似于正常铁电体,其老化起因于畴壁运动;而高温长时间烧结的复相陶瓷表现为典型弛豫电体的老化行为,起因于缺陷偶极子与极性微区的相互作用。     

铅系复合钙钛矿Pb（Fe1／2Ta1／2）O3铁电陶瓷的介电弛豫特性

用普通合成法制备了纯钙钛矿结构相的Ｐｂ（Ｆｅ１／２Ｔａ１／２）Ｏ３（ＰＦＴ）陶瓷，并进行了９００℃退火热处理。对其介电性质测试结果表明，未热处理与热处理过的ＰＦＴ陶瓷在０．１￣１００ＫＨｚ频率下均表现出介电弥散性转变。未热处理的ＰＦＴ陶瓷最大介电常数对应的温度（Ｔ０）不随测量频率变化；热处理过的ＰＦＴ陶瓷在此频率范围Ｔ０值表现出明显的频率依赖性（频率色散），即△Ｔ０＝５℃。由此可以认为ＰＦＴ是弛豫     

铌铁酸铅PFN的结构无序及介电相变特性

运用高分辨透射电镜显微技术观察到ＰＦＮ中Ｂ位离子呈无序排列，不易形成有序结构，在性能上，ＰＦＮ的介电常数ε和介电损耗ｔｇδ均很大，相变扩散度小；相应时的介电行为，热容和热膨胀的变化比较特殊。     

Sm掺杂PMN–PT弛豫铁电陶瓷的大信号径向谐振响应

弛豫铁电材料因具有高的介电常数和压电系数而广泛应用于致动器、换能器等领域。实际使用中往往需要施加大信号激励驱动谐振,因此了解掌握大信号激励下的谐振特性变化极为重要。然而,目前这方面的研究却少有文献报道。针对这一问题,以二步氧化物固相反应法制备了高压电性Pb_0.9625Sm_0.025[(Mg_1/3Nb_2/3)_0.71Ti_0.29]O₃陶瓷材料,用本人搭建的大信号谐振响应测试系统研究了驱动场幅值和温度对径向谐振特性的影响。结果表明：低驱动场下谐振响应能保持单一谐振峰直至完全退极化,但随着驱动场的增大谐振响应变得复杂,即使在低温也呈现多个谐振峰。谐振特性的变化与机械品质因子Q_m、铁电宏畴尺寸及相组成密切相关,低Q_m材料在大驱动场下产生的内热加速了宏畴裂解并引发了二级铁电相变。谐振特性的不稳定及较大谐振频率温度系数限制了Sm改性PMN–PT弛豫铁电陶瓷的应用,尤其是在大信号下。     

单步法合成铌镍酸铅基铁电陶瓷及其性能

采用单步法合成了铌镍酸铅基铁电陶瓷，研究了合成过程中钙钛矿结构的形成及其介电铁电性能。X射线衍射结果表明，加入65mol％过量的PbO即可形成单一的钙钛矿相，观察其微观结构、测试其介电和铁电性能，结果表明，1200℃为最佳烧成温度，此温度烧结的陶瓷样品可以获得18000的介电常数。该方法为合成铅基弛豫铁电体提供了新的途径。     

低温烧结PMZN陶瓷老化行为的初步研究

镁、锰同时掺杂的ＰＭＮ－ＰＺＮ－ＰＴ低烧陶瓷表现出明显的介电老化现象，恒温老化时，材料室温的介电常数及介电损耗随时间延长而下降，在室温下老化约１００ｈ后介电性能基本稳定。老化过程中的一定时间范围内，介电常数或电容变化率与老化时间的对数值呈线性关系。材料老化的程度与老化温度密切相关。     

PLZT陶瓷的介电弛豫行为与A位有序

用传统粉末工艺合成了（Ｐｂ＿（０．８６５）Ｌａ＿（０．０９））（Ｚｒ＿（０．６５）Ｔｉ＿（０．３５））Ｏ＿３陶瓷（ＰＬＺＴ９／６５／３５）。Ｘ射线研究表明：试样中存在着Ａ位准体心立方有序超结构，有序畴的平均尺寸为１０～２０ｎｍ。测定了１０个频率下介电常数与温度的关系，并将介电常数最大值的温度Ｔ＿ｍ与对应的频率ｆ用Ｖｏｇｅｌ－Ｆｕｌｃｈｅｒ公式拟合，得到物理上合理的激活能及指数前项值，这表明试样的介电弛豫行为与自旋玻璃态类似。基于Ａ位有序超结构及类似于自旋玻璃态的极化行为，对试样的极化全过程进行了探讨。     

锰锑酸铅-锌铌酸铅-锆钛酸铅陶瓷的铁电性能

通过电滞回线测试,探讨了xPb(Mn1/3Sb2/3)0.05(Zr1/2Ti1/2)0.95O3(1-x)Pb(Zn1/3Nb2/3)0.28(Zr1/2Ti1/2)0.72O3[xPMnS-(1-x)PZN]陶瓷的铁电性能及铁电相变特性.同时研究了Ba2 取代Pb2 对材料铁电性能的影响.结果表明;三方相含量较高的0.2PMnS-0.8PZN陶瓷具有较高的矫顽场和较大的剩余极化强度;四方相含量较高的0.5PMnS-0.5PZN和0.6PMnS-0.4PZN陶瓷具有较低的矫顽场和较小的剩余极化强度,Ba2 取代使三方相含量增加,铁电性能明显提高.     

Ferroelectric to Relaxor Transition in BaTiO3–Bi(Zn2/3Nb1/3)O3 Ceramics

The (1?x)BaTiO₃–xBi(Zn_2/3Nb_1/3)O₃ (x = 0.01–0.30) ceramics were synthesized by solid‐state reactions. The solubility limit was determined to be x = 0.20. A systematic structural transition from a tetragonal phase (x ≤ 0.034), to a mixture of tetragonal and rhombohedral phases (0.038 ≤ x ≤ 0.20), and finally to a pseudocubic phase (x ≥ 0.22) at room temperature was identified. Dielectric measurement revealed a ferroelectric (x ≤ 0.04) to relaxor (x ≥ 0.06) transition with permittivity peak broadening and flattening, which was further verified by Raman spectroscopy and differential scanning calorimetry (DSC). Activation energies obtained from the Vogel–Fulcher model displayed an increasing trend from ~0.03 eV for x ~ 0.05, to unusually high values (>0.20 eV) for the compositions with x ≥ 0.15. With the increase in Bi(Zn_2/3Nb_1/3)O₃ content, the polarization hysteresis demonstrated a tendency from high nonlinearity to sublinearity coupled with the reduction in remnant polarization and coervice field. The deconvolution of the irreversible/reversible polarization contribution was enabled by first‐order reversal curve distributions, which indicates that the decreasing polarization nonlinearity with the increase in Bi(Zn_2/3Nb_1/3)O₃ concentration could be related with the change from the ferroelectric domain and domain wall contributions to the weakly coupled relaxor behaviors.     

Preparation and characterization of Pb(Lu1/2Nb1/2)O3–Pb(In1/2Nb1/2)O3–PbTiO3 ternary ferroelectric ceramics with high phase transition temperatures

To explore new relaxor‐PbTiO₃ systems for high‐power and high‐temperature electromechanical applications, a ternary ferroelectric ceramic system of Pb(Lu_1/2Nb_1/2)O₃–Pb(In_1/2Nb_1/2)O₃–PbTiO₃ (PLN–PIN–PT) have been investigated. The phase structure, dielectric, piezoelectric, and ferroelectric properties of the as‐prepared PLN–PIN–PT ceramics near the morphotropic phase boundary (MPB) were characterized. A high rhombohedral‐tetragonal phase transition temperature T_R‐T of 165°C and a high Curie temperature T_C of 345°C, together with a good piezoelectric coefficient d₃₃ of 420 pC/N, were obtained in 0.38PLN–0.20PIN–0.42PT ceramics. Furthermore, for (0.8?x)PLN–0.2PIN–xPT ceramics, the temperature‐dependent piezoelectric coefficients, coercive fields and electric‐field‐induced strains were further studied. At 175°C, their coercive fields were found to be above 9.5 kV/cm, which is higher than that of PMN–PT and soft P5H ceramics at room temperature, indicating PLN–PIN–PT ceramics to be one of the promising candidates in piezoelectric applications under high‐driven fields. The results presented here could benefit the development of relaxor‐PbTiO₃ with enhanced phase transition temperatures and coercive fields.     

Ferroelectric Ceramics in the PbMg1/3Nb2/3O3-PbCd1/3Nb2/3O3 System

Solid solutions (1-x)PbMg_1/3Nb_2/3O₃ + xPbCd_1/3Nb_2/3O₃ with x = 0-0.30 are investigated with purpose to work out a capacitor ceramics with good dielectric properties and low sintering temperature. It is found that the perovskite phase forms at sintering near to 980°C and begins to decompose at higher temperatures. When x grows from 0 to 0.30, the Curie temperature linearly grows from -10°C to +25°C, the dielectric permittivity ε_m in the Curie point T_C decreases from 18000 to 6800 and the phase transition becomes more diffused. The dielectric permittivity at room temperature is rather high and the temperature stability is improved. The system is of interest, because it can serve as a base for working out some ceramic materials for capacitors with low sintering temperature, which needs of no special atmosphere at burning.     

前驱体制备(1-x)CaTiO3-xCa(Zn1/3Nb2/3)O3陶瓷的微波介电性能

以ZnNb2O6为前驱体,通过固相反应合成了(1-x)CaTiO_3-xCa(Zn_(1/3)Nb_(2/3))O_3体系微波介质陶瓷。对固溶体进行了结构与性能测试,研究了体系结构与性能随组份变化规律。结果表明,由于Zn,Nb对Ti的B位取代增大了B-O八面体的倾斜角,从而导致随着Ca(Zn_(1/3)Nb_(2/3))O_3含量从0.2增加至0.8,介电常数从109减小为49,Q×f值从8340GHz增至13200GHz,频率温度稳定系数由321ppm/℃降为-18ppm/℃。在x=0.7时获得ε_1≈56,Q×f≈11500GHz,τ_f≈-5ppm/℃的最佳性能。     

铌镁酸钙/钛酸钙多层异质薄膜中的晶格失配与粗糙度累积

采用Pechini法制备Ca(Mg1/3Nb2/3)O3(CMN)及CaTiO3(CT)前驱体溶液,用液相旋涂技术按照一定的排布方式制备了总厚度相同而异质界面数不同的CMN/CT异质结构介电薄膜。研究表明:无论是CMN还是CT,其同质层间均会由于前一层的籽晶作用而产生粗糙度的累积,从而对其相结构、微观形貌和介电性能产生不利影响。异质层间的晶格失配可以消除这种粗糙度累积效应,改善薄膜的相结构和微观形貌。随着薄膜中异质界面数的增加,获得了结晶较好的单一钙钛矿结构异质薄膜,薄膜表面粗糙度降低,介电性能得到提高。     

Re‐entrant relaxor behavior in BaTiO3‐Bi(Zn2/3Nb1/3)O3 ceramics

The (1?x)BaTiO₃?xBi(Zn_2/3Nb_1/3)O₃ (x=0.10‐0.25) ceramics were fabricated via solid‐state reactions. Temperature‐dependent polarization measurement reveals that with the temperature lowering, the remnant polarization increases till a maximum value before it decreases, showing a reentrant phenomenon. Absence of apparent switching current peaks in the current density as a function of electric field should indicate the lack of a ferroelectric transition, which is further verified by the consistent macroscopic phase structure from the Raman spectra. An anomalous peak in the full width at half maximum of a deconvoluted mode at ~515 cm^?1 suggests the entering of a more disordered state of dipolar dynamics, which may be originated from the competition between the freezing of polar nanoregions and the random interacting fields.     

锂离子电池正极材料LiNi_(1/3)Co_(1/3)Mn_(1/3)O_2的研究进展

锂离子电池正极材料Li Ni1/3Co1/3Mn1/3O2具有比商业化正极材料——LiCoO2更低廉的成本、更低的毒性、更好的热稳定性,近年来受到广大科研工作者的关注。主要介绍了Li Ni1/3Co1/3Mn1/3O2正极材料的合成改性方法及其近年来在电化学性能方面所取得的成果和进展,并简要概括了该材料结构和发展趋势。不断提高Li Ni1/3Co1/3Mn1/3O2正极材料的振实密度以及电化学性能特别是其在高倍率充放电条件下的循环性能将成为相关科研工作者的研究重点。     

BiFeO3-SrBi2Nb2O9陶瓷的介电与铁电性能研究

用传统的固相反应法制备了单相层状钙钛矿结构的xBiFeO3-(1-x)SrBi2Nb2O9(x=0、0.05、0.1)的铁电陶瓷,并对其电学性能进行了研究。研究结果表明BiFeO3的掺入降低了SBN的烧结温度,陶瓷晶粒尺寸减小,致密度提高;介电性能得到了改善,居里温度和在居里点的介电常数提高;铁电性能恶化,耐压特性下降。     

固相反应法钙钛矿型Pb（Zn1／3Nb2／3）O3的合成

用XRD法研究了八面体择位能大的离子对合成钙钛矿型Pb(Zn_(1/3)Nb_(2/3))0_3[PZN]多晶材料的影响。通过对PZN结晶化学参数的分析,认为八面体择位能大的Mn~(3 )离子能有效的抑制焦录石的形成。结果表明在PZN中添加1wt％MnCO_3就能获得完全无焦录石的钙钛矿型结构的PZN陶瓷。文中讨论了相组成和钙钛矿相的稳定机理。