PMZNT弛豫铁电陶瓷在不同外电场下的介电特性

对PMN-PZN-PT弛豫铁电陶瓷在不同外电场下的介电特性进行了研究. 结果表明:直流偏压场与交流测试场对弛豫铁电体的作用相反,增大偏压场导致介电常数的降低,而增大测试场则使介电常数升高. 同时频率色散度也呈现了不同的变化趋势. 利用超顺电理论及多畴态模型对上述结果进行了定性分析.     

PLZT驰豫铁电陶瓷偏压压电效应的研究

本文研究了铌掺杂的ＰＬＺＴ驰豫铁电陶瓷在不同直流偏压及温度下的介电常数ε３３,平面机电耦合系数ｋ和等效横向压电常数ｄ３１。实验表明,铌掺杂的ＰＬＺＴ驰豫铁电陶瓷ｄ３１值可由直流偏压控制及ｄ３１值的温度系数远小于ＰＭＮ－ＰＴ系陶瓷。室温上２ｍｏｌ％和３ｍｏｌ％的铌掺杂的ＰＬＺＴ１０／６５／３５驰豫铁电陶瓷在１０ＫＶ／ｃｍ的偏压下│ｄ３１│分别为２０５ｐＣ／Ｎ和１６０Ｃ／Ｎ。     

PZN－PT－PMN电致伸缩陶瓷的介电性质

对（１－ｘ－ｙ）ＰＺＮ－ｘＰＴ－ｙＰＭＮ（０＜ｘ＜０．１，０＜ｙ＜１）陶瓷的电致伸缩与介电特性进行了系统的研究。利用ＸＲＤ定性分析了在相同工艺条件下，组成及Ｋ~＋，Ｌａ~（３＋），Ｙ~（３＋），Ｗ~（６＋）等掺杂离子对微观结构、电致伸缩及介电性质的影响。分析表明：施主、受主离子掺杂对钙钛矿相的生成有不同的作用，掺杂后的材料介电常数均减小；而电致伸缩系数增大，其中适当掺Ｋ~＋和过量ＭｇＯ可使应变量得到提高；而过量ＺｎＯ使应变量减小。ＰＺＮ－ＰＴ－ＰＭＮ的应变性质和温度特性均优于ＰＺＮ，三元系的电致伸缩特性与各组成含量有关，其中铁电相含量的增大是应变量增大的原因。     

溶胶-凝胶法制备PbTiO3基铁电陶瓷的高频晶粒尺寸效应

首次报道了溶胶－凝胶法制备钛酸铅基铁电陶瓷的晶粒尺寸对其高频介电性能的影响。实验研究表明,铁电陶瓷的高频介电弛豫主要是由材料内部的畴壁共振引起的,晶粒尺寸增加,畴壁尺寸增大,介电弛豫向低频移动,反之,晶粒尺寸减小,畴壁尺寸变小,介电弛豫向高频移动 。     

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     

聚氨酯弹性体电致伸缩性能研究

以聚(己二酸-丁二醇-新戊二醇)酯二元醇、甲苯二异氰酸酯、1,4-丁二醇和三羟甲基丙烷为原料,经聚合得到了一系列聚氨酯弹性体。利用LCR阻抗分析仪研究了所得聚氨酯弹性体的介电性能。在1kHz频率下聚氨酯弹性体的相对介电常数为7左右,相对介电常数随测试频率的增加而降低。采用数字散斑相关测量方法研究了聚氨酯弹性体在电场诱导下的应变─电致伸缩响应之间的关系。结果表明,聚氨酯弹性体在外加高压电场的作用下,随着高压电源的开合,其应变也随之呈现出相应的收缩与回复,其电致伸缩系数随聚氨酯弹性体密度的增加及相对介电常数的减小而降低。     

MnO2对0.85Pb（Zn1／3Nb2／3）O3—0.15BaTiO3陶瓷弛豫现象的影响

研究了ＭｎＯ２掺杂对０．８５Ｐｂ（Ｚｎ１／３Ｎｂ２／３）Ｏ３－０．１５ＢａＴｉＯ３陶瓷电介电、热释电以及铁电弛豫等性能的影响。添加ＭｎＯ２使ＰＺＮ－ＢＴ陶瓷的介电常数ε下降，室温老化率明显增大。随着ＭｎＯ２含量的增加，ＰＺＮ－ＢＴ陶瓷介电常数与温度的关系中所表现出来的频率弛豫现象逐渐减弱，直到消失，但其扩散相变现象仍然十分明显。     

聚苯胺包覆二氧化硅电流变液的介电弛豫谱研究

低温包覆聚苯胺的方法对球形二氧化硅粒子进行了表面改性,利用介电弛豫谱分析了聚苯胺包覆后的二氧化硅电流变液介电性质的变化。结果表明包覆聚苯胺后,电流变液的介电增量显著提高,弛豫频率向高频移动。两种变化均对体系的电流变效果起到积极的作用。另外还发现可以通过调整碱液的pH值改变电流变液的弛豫频率,从而提高改变电流变的电场响应能力。     

MnO_2对0．85Pb（Zn_（1／3）Nb_（2／3））O_3－0．15B

研究了ＭｎＯ＿２掺杂对０．８５Ｐｂ（Ｚｎ＿（１／３）Ｎｂ＿（２／３））Ｏ＿３－０．１５ＢａＴｉＯ＿３陶瓷电、热释电以及铁电弛豫等性能的影响。添加ＭｎＯ＿２使ｐＺＮ－ＢＴ陶瓷的介电常数ε下降，室温老化率明显增大。随着ＭｎＯ＿２含量的增加，ＰＺＮ－ＢＴ陶瓷介电常数与温度的关系中所表现出来的频率弛豫现象逐渐减弱，直至消失，但其扩散相变现象仍然十分明显。     

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。     

Effect of electron beam irradiation on mechanical and dielectric properties of polypropylene films

In the present investigation the effect of electron beam irradiation on the mechanical properties of thin films of Polypropylene (PP) were measured. The dielectric properties of PP films were carried out in the frequency range from 20 Hz to 1 MHz at various DC bias potential. All measurements were carried out at room temperature. It is found that the electron beam irradiation caused an increase in Young's Modulus of PP film dose of up to 70 kGy were applied, but tensile strength and % elongation at break were found to be decrease with the increasing dose rate. The significant changes were observed in the case of dielectric constant and dielectric loss for electron irradiated PP films. The DSC results indicate that irradiation on PP films changes the thermal behavior. Minor differences in FTIR spectra were observed after irradiation treatment. It is observed that, the effect of radiation damage results in improvement in mechanical strength of the films. The increased dielectric constant and dependence of the bias voltage in case of irradiated and unirradiated PP films has been reported. It is suggested that, the PP films modified with the electron beam irradiation can be used as a good dielectric material for different electronic devices. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Influence of Grain and Grain‐Boundary Resistances on Dielectric Properties of KNbO3 Under Small DC Bias Field

Lead‐free piezoelectric potassium niobate (KNbO₃) system was synthesized by conventional solid‐state ceramic route. Rietveld analysis of X‐ray diffraction data of this system revealed that the sample crystallized in pure orthorhombic perovskite phase at room temperature. SEM micrograph of this system depicted presence of grains having diffuse brick structure with an average grain size of 500 nm. Dielectric properties of KNbO₃ ceramic were investigated under different DC bias voltage in a broad frequency (from 20 Hz to 1 MHz) and temperature (from 200°C to 500°C) ranges in its three crystalline phases. The dielectric constant was found to increase with increasing bias field in all three phases. The loss tangent of this system was found to increase first, and then it becomes constant with increasing bias field. These properties have been explained in terms of variation of grain and grain‐boundary resistances with bias field.     

Modeling of Dielectric Behaviors of Multilayer Ceramic Capacitors Under a Direct Current Bias Field

A modified Campbell model has been provided considering the internal stress and the "core-shell" microstructure that occurs in X7R-type multilayer ceramic capacitors (MLCCs). The capacitance stability coefficient α was defined to denote the effect of a direct current (DC) bias field on the capacitance of MLCCs. According to this model, the dielectric constant will decrease with DC bias field while the α coefficient will increase. The dielectric properties of MLCCs with different active layers, sintering temperatures, grain size, and strontium doping concentration were measured in order to verify the validity of the model. The experimental results exhibited good agreement with the model, which provided qualitative explanations.     

Photosensitive polynorbornene based dielectric. I. Structure–property relationships

In the microelectronics industry, the drive for increasing device speed, level of functionality and shrinking size has placed significant demands on the performance characteristics of polymer dielectrics. In this study, a negative acting, photodefinable dielectric formulation based on a copolymer of decylnorborne (decylNB) and epoxynorbornene (AGENB) was investigated for use in electronics packaging. The structure–property relations of this copolymer were investigated. Copolymer composition and processing conditions were shown to significantly affect the properties of the final polymer films. A lower content of AGENB results in lower moisture absorption, dielectric constant, modulus and residual stress, but it compromises multilayer capability. High crosslink density lowers the dielectric constant but increases the modulus and residual stress. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3023–3030, 2004     

Influence of external electric field on relaxor behaviour of (Pb0.75Ba0.25)(Zr0.70Ti0.30)O3 ceramics

The effects of the external d.c. and a.c. electric field on the dielectric response and relaxor behaviour of lead–barium–zirconate–titanate (PBZT) ceramics of the composition Ba/Zr/Ti 25/70/30 have been studied. The significant influence of the strength of the d.c. bias field and the amplitude of the a.c. field on the dielectric constant maximum and frequency dispersion was determined. The magnitude of the dielectric response strongly decreases under the bias field and increases with the increase of the a.c. field amplitude. All parameters describing the relaxor behaviour of the studied ceramics changed under the external d.c. and a.c. electric field. The experimental results can be explained in terms of existing models of relaxors.     

Humidity Dependence of Apparent Dielectric Constant for DSP Cement Materials at High Frequencies

The relationship between humidity and dielectric constant for cement densified with small particles (DSP) has been studied in the relative humidity range 0%-93% and the frequency range 1 MHz to 1 GHz. The calculated dielectric constant appears to increase with increasing humidity as a linear relation at fixed frequency. According to experimental data and basic principles for dielectrics, two experimental expressions are suggested for heterogeneous dielectric materials to describe the observed behavior of the dielectric constant. The expressions fit the experimental data well in the frequency range studied. Apparent dielectric constant decreases with increasing frequency. Polarization of DSP cement is also discussed.     

Lead magnesium niobate-filled silicone dielectric elastomer with large actuated strain

A silicone dielectric elastomer filled with lead magnesium niobate with a maximum actuated strain of 7.4% at 45 kV/mm was fabricated by optimizing the amount of dielectric filler, amount of plasticizing agent, and crosslink density of the elastomer. The actuated strain of dielectric elastomers (DEs) is determined by both the dielectric constant and the elastic modulus. Although the dielectric constant of the silicone elastomer increased with increasing loading amount of lead magnesium niobate, actuated strain did not increase as expected because the elastic modulus increased at the same time. The elastic modulus of silicone dielectric elastomer was decreased by reducing the crosslink density or adding plasticizing agent, leading to a visible increase in actuated strain. It was also revealed that actuated strain of silicone dielectric elastomer always goes up with increasing ratio of dielectric constant to elastic modulus. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Evaluation of Residual Stress in a Multilayer Ceramic Capacitor and its Effect on Dielectric Behaviors Under Applied dc Bias Field

The residual stress in a multilayer ceramic capacitor (MLCC) has been evaluated by two-dimensional finite element simulation in combination with X-ray diffraction measurement. It is shown that there is a compressive in-plane stress in the active layers of the MLCC, which increases with increases in the number of dielectric layers when both dielectric layer thickness and electrode thickness are kept constant. A good order of magnitude agreement between the residual stresses obtained from two approaches is found. The ɛ– V response of the MLCC with different number of dielectric layers demonstrates that under a given or no applied field, the dielectric permittivity increases with increasing compressive stress. Additionally, under dc bias field, the higher the compressive in-plane stress existing in the MLCC, the more significant the decrease of the dielectric permittivity. These results can be explained through a phenomenological thermodynamic model, including both elastic and electrostatic energy, based on the Ginsburg–Landau–Devonshire theory.     

Electrical properties of flexible graphene reinforced polyimide composites

The electrical properties of polyimide and the composite at different volumes fractions were studied in the frequency range 200–20 kHz and in the temperature range 30–200 °C. Increasing the volume fraction of graphene up to 10%, resulted in an extremely large increase in the dielectric constant, which indicates the composites remarkable ability to store electric potential energy under the effect of alternating electric field. An increase in dielectric constant was also observed with increasing temperature and decreasing frequency. The outstanding dielectric properties of polyimide graphene nanocomposites are attributed to the large volume fraction of interfaces in the bulk of the material. The measured increase in dielectric constant with increasing temperature was attributed to the segmental mobility of the polymer chains. The AC conductivity for polyimide and the composites was calculated from the loss factor and a remarkably high conductivity was obtained for the composites due to the formation of conducting paths in the matrix by the graphene sheets. Also this study showed that the thermal conductivity of the composites increased sharply with increasing graphene concentration. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45372.     

粘结层对压电纤维复合材料机电响应行为的影响

本文从功能材料力-电耦合的角度分析了粘结层参数对压电纤维复合材料(macro fiber composites, MFC)机电响应行为的影响。通过有限元模拟计算发现,减少粘结层厚度及增大其介电常数有利于缓解MFC介电失配现象,提高有效电场加载,从而获得高压电性。试验制备了MFC并进行了驱动及传感性能表征,试验结果与模拟仿真一致。减少粘结层厚度和弹性模量,及增大其介电常数,能有效增大MFC尖端位移和输出电压,提高驱动和传感性能。该研究对驱动和传感用MFC的设计提供了指导。