ZnO/PVDF压电复合材料的制备及性能

采用超声模板法制备了平行束状纳米ZnO晶须,将其与压电高聚物PVDF复合,用热压法制备六种含平行晶须状纳米ZnO不同质量分数与不同形态、尺寸的ZnO的ZnO/PVDF复合材料。经取向、极化后对其结构、形态及介电性和压电性能进行了系统测试。结果表明:尺寸与形态对压电复合材料的影响极大,球型、准球型、四针状纳米ZnO和非纳米ZnO与无定型PVDF复合,虽经同样条件极化处理,并无压电性能产生。与传统观念不同,即使主体为PVDF,但随着平行晶须状纳米ZnO含量的增加,电性能参数呈非线性增大,在ZnO含量仅为15%左右时就产生了复合材料介电常数ε和压电常数d33值的转折性突跃,与单一压电高聚物材料相比显著增加,且极化性能得到明显提高。     

0-3 PZT/PVDF 压电复合材料的制备及其性能

采用溶液混合法制备PZT/PVDF压电复合材料。首先用水热法制备出适合溶液混合的PZT陶瓷粉末,并根据陶瓷粉末对PVDF的吸收量,选择乙醇作为PVDF的溶剂进行混合,然后烘干制备PZT/PVDF复合粉末,再成型极化。实验结果表明,这种复合方法提高了PZT陶瓷颗粒在PVDF有机基体中的分散度,使材料内部均匀,结构致密,从而提高了PZT/PVDF压电复合材料的压电和介电性能。      

电场对(Ba0.97Ca0.03)(Ti0.82Zr0.18)O3无铅压电陶瓷铁电性的影响

采用溶胶-凝胶方法制备了(Ba0.97Ca0.03)(Ti0.82Zr0.18)O3无铅压电陶瓷。在电场1～8kV/cm下,频率为0.01～10Hz范围内,对其电滞回线进行了分析。实验结果表明(Ba0.97Ca0.03)(Ti0.82Zr0.18)O3陶瓷的电滞回线随电场值和频率的变化明显,在低电场下,随着频率的增加矫顽场(Ec)单调减小,在低频下剩余极化(Pr)增加;而在高电场下,随着频率的增加Ec单调增大,电滞回线达到饱和时,电滞回线随不同测试频率无明显变化。     

定向BaTiO3晶须/PVDF压电复合材料的制备及性能研究

以高度定向的BaTiO3晶须作为活性相、聚偏氟乙烯(PVDF)作为基体制备了压电复合材料，研究了该复合材料的介电和电学性能，研究结果表明，以BaTiO3作为活性相的晶须复合材料与粉末复合材料相比，其介电常数(ε)、压电常数(d33)和剩余极化率(Pr)大大提高，而其损耗因子(tanδ)具有相反的趋势，对晶须复合材料，沿晶须定向方向的ε、d33和Pr的值比晶须平行方向要高得多，分析了产生这些差别的原因。     

Sm2O3掺杂(Ba0.7Ca0.3)TiO3-Ba(Zr0.2Ti0.8)O3无铅压电陶瓷的制备与性能

采用固相合成法制备了Sm2O3掺杂的(Ba0.7Ca0.3)TiO3-Ba(Zr0.2Ti0.8)O3(BCZT)无铅压电陶瓷.借助XRD、SEM等手段对该陶瓷的显微结构与电性能进行了研究.结果表明,Sm2O3的掺杂降低了BCZT无铅压电陶瓷的烧结温度并使居里温度点Tc从85℃提高到95℃.当Sm2O3掺杂量为0.02wt%～0.1wt%时,样品具有典型ABO3型钙钛矿结构.Sm2O3掺杂量为0.02wt%时,所得陶瓷样品具有最优综合电性能,其压电常数d33、机电耦合系数kp、机械品质因子Qm、介电损耗tanδ和介电常数εr分别为590 pC/N、0.52、43、1.3%和3372.     

磁控溅射制备(Pb1-xSrx)TiO3系铁电薄膜的实验研究

钛酸锶铅((Pb1-xSrx)TiO3,PST)固溶体材料是一种性能优良的钙钛矿型铁电材料,其形成铁电相的温度较低,且易于和半导体工艺结合,应用潜力较大.本文采用磁控溅射法制备了PST薄膜,并初步研究了其介电和铁电特性.结果表明,磁控溅射得到的PST薄膜必须进行一定的热处理,才能使之转变为具有铁电性的钙钛矿结构的铁电薄膜.其介电特性与测试频率有关,试样的饱和极化强度可达19μC/cm2,剩余极化强度可达6.6μC/cm2,矫顽场强达16kV/cm,热释电系数达10-4C/m2*K量级,表明所制备的PST薄膜具有良好的铁电性.     

添加Ni和Ag纳米颗粒对BaTiO3/PVDF复合材料击穿场强的影响

选用金属Ni和Ag纳米颗粒作为导体相,采用共混法分别制备了击穿场强较高的Ni-BaTiO₃/聚偏氟乙烯（Ni-BaTiO₃/PVDF）和Ag-BaTiO₃/PVDF三相复合材料。研究了导体相Ni和Ag添加量、粒径及导体种类对复合材料击穿场强的影响,发现Ni-BaTiO₃/PVDF和Ag-BaTiO₃/PVDF三相复合材料的击穿场强均随导体添加量的增加呈现先升高后降低的趋势,且在适宜的导体添加量下复合材料均表现出高于未添加导体相的BaTiO₃/PVDF两相复合材料的击穿场强;添加同类导体Ni时,Ni粒径越小,三相复合材料的击穿场强提高越明显;导体添加量与粒径均相同时,Ni-BaTiO₃/PVDF复合材料的击穿场强较高,当粒径50 nm的Ni添加量为体积分数1.90%时,其击穿场强可达200 kV/mm,储能密度比BaTiO₃/PVDF两相复合材料提高4倍。这些结果可用库仑阻塞效应很好地解释。     

Mn掺杂(K 0.5 Na 0.5 ) 0.96 Sr 0.02 NbO3无铅压电陶瓷的研究

采用常压烧结方法制备了Mn掺杂的（K0.5Na0.5）0.96Sr0.02Nb1-xMnxO3无铅压电陶瓷.研究了Mn含量对该体系材料的相组成、微观结构、介电、压电和热稳定性能的影响.XRD表明随着Mn含量的增加,体系由正交相过渡到赝四方相;而且,富Na的第二相消失,得到纯净的钙钛矿相结构.在Mn含量为x=0.03和0.04时,观察到了两个温度（200和390℃）处的介电反常,这和晶格畸变引起的复晶胞结构有关.Mn含量为x=0.02时,得到综合性能优良的压电超声换能器用材料：介电常数ε^T33/ε0=479,压电常数d33=121pC/N,机电耦合系数Kp=41%,机械品质因子Qm=298,介电损耗tanδ=1.6%,居里温度Tc=391℃,谐振频率αfr和机电耦合系数Kp随温度的变化率αfr（80℃）和αKp（80℃）分别为-1.85%和1.19%.     

Bi2O3/BiOCl异质复合材料的制备及其光催化性能

本文以五水硝酸铋和氯化钾为原料,利用水热法一步制备了Bi2O3/BiOCl异质复合光催化材料,采用X射线粉末衍射(XRD)、扫描电镜(SEM)和紫外可见漫反射光谱(UV-Vis)对样品进行了表征。以罗丹明B为目标降解物,研究n(Bi)/n(Cl)摩尔比对合成Bi2O3/BiOCl异质复合光催化剂的形貌和光催化性能的影响。结果表明:随着n(Bi)/n(Cl)摩尔比的增加,Bi2O3/BiOCl的光催化活性显著增强,在n(Bi)/n(Cl)=1.75时,制备的Bi2O3/BiOCl异质复合光催化材料具有最高的光催化活性。     

rGO/PANI/MnO2三元复合材料的制备和电化学性能

用水热合成法和冻干操作制备石墨烯/聚苯胺/二氧化锰三元复合材料(rGO/PANI/MnO₂),使用X射线衍射(XRD)、X射线光电子能谱(XPS)和扫描电子显微镜(SEM)对其进行了表征。结果表明,用这种简单高效的方法制备的复合材料,具有相互交联的网络状结构和自支撑特性。在反应过程中MnO₂与聚苯胺形成不规则的块状结构,共沉积在石墨烯自组装形成的网络片层上。这种复合材料具有良好的电容性能,比电容为388 F·g-1(0.5 A·g^-1),优于单纯的石墨烯(rGO,234 F·g-1)和聚苯胺电极(PANI,176 F·g-1)。使用这种复合材料作为正极、rGO作为负极组装的一种不对称超级电容器,能在0～1.6 V范围内可逆循环,功率密度为17.48 W·kg^-1时最大能量密度为13.5 Wh·kg^-1。     

Preparation of Pb0.98La0.02(Zr0.65Ti0.35)O3 films and their fine patterning

The photosensitive lanthanum-doped lead zirconate titanate (PLZT) gel films were prepared by chemical modification with acetylacetone (AcAcH), and their fourier transform infrared (FT-IR) spectra and ultraviolet visible (UV-Vis) spectra were measured. The results show that the chelate rings of AcAcH with Ti or Zr are formed in the PLZT gel films. With irradiation of UV light, the chelate rings are photolyzed, and lead to a change of the solubility of the PLZT gel films in methanol. Transmission electron microscope (TEM) observations show that the perovskite phase is crystallized in PLZT thin film after heat treatment at 700 °C, whose grain sizes are less than or equal to 60 nm. The PLZT thin films exhibited hysteresis loops and good fatigue properties.     

Electrical properties of Pb0.97La0.02(Zr0.95Ti0.05)O3 antiferroelectric thin films on TiO2 buffer layer

Pb_0.97La_0.02(Zr_0.95Ti_0.05)O₃ antiferroelectric thin films with thickness of 500 nm were successfully deposited on TiO₂ buffered Pt(1 1 1)/Ti/SiO₂/Si(1 0 0) and Pt(1 1 1)/Ti/SiO₂/Si(1 0 0) substrates via sol-gel process. Microstructure of Pb_0.97La_0.02(Zr_0.95Ti_0.05)O₃ thin films was studied by X-ray diffraction analyses. The antiferroelectric nature of the Pb_0.97La_0.02(Zr_0.95Ti_0.05)O₃ thin films was confirmed by the double hysteresis behaviors of polarization and double buffer fly response of dielectric constant versus applied voltage at room temperature. The capacitance-voltage behaviors of the Pb_0.97La_0.02(Zr_0.95Ti_0.05)O₃ films with and without TiO₂ buffer layer were studied, as a function of temperature. The temperature dependence of dielectric constant displayed a similar behavior and the Curie temperature (T_c) was 193 °C for films on both substrates. The current caused by the polarization and depolarization of polar in the Pb_0.97La_0.02(Zr_0.95Ti_0.05)O₃ films was detected by current density-electric field measurement.     

Microgeometry effect on the properties of Pb0.99(Zr0.95Ti0.05)0.98Nb0.02O3 ferroelectric ceramics

Porous Pb_0.99(Zr_0.95Ti_0.05)_0.98Nb_0.02O₃ ferroelectric ceramics with different pore size were prepared by solid-state sintering in air. The microstructural effect on the properties has been systematically investigated by SEM, ferroelectric hysteresis, strain-electric field curves and breakdown strength measurements. The results demonstrate that the microgeometry has a subtle effect on the ferroelectric and dielectric properties. However, the results also demonstrate that the electric field induced strain and the dielectric breakdown strength decreases with the increase of pore size.     

Polarization fatigue and photoinduced current in (Pb0.72La0.28)Ti0.93O3 buffered Pb(Zr0.52Ti0.48)O3 films on platinized silicon

We report a study on the fatigue behavior of Pb(Zr_0.52Ti_0.48)TiO₃ (PZT) films deposited on Pt/Ti/SiO₂/Si substrates by a sol-gel method with single- and double-sided (Pb_0.72La_0.28)Ti_0.93O₃ (PLT) buffer layers, with an attempt to clarify the role of the top and bottom PLT buffer layers on the fatigue endurance (FE) of the PZT films. It is revealed that the existence of the PLT buffer layer and the level of driving alternating-current electric switching field strongly influence the fatigue properties. In terms of the existence of an asymmetric built-in electric field near the top and bottom interfaces between the film and metal electrode, we explain the observed fatigue properties.     

Quantitative dependence of the properties of Pb0.99(Zr0.95Ti0.05)0.98Nb0.02O3 ferroelectric ceramics on porosity

Porous Pb_0.99(Zr_0.95Ti_0.05)_0.98Nb_0.02O₃ ferroelectric ceramics with a pore size of the order of the crystalline grain size were prepared and the microstructure and the properties were investigated. Based on this microstructure, the net porosity of the ceramics can be attributed to the intentionally introduced extrinsic porosity and thus the quantitative dependence of ferroelectric and dielectric properties of the ceramics on the porosity can be established respectively. A good agreement with experimental measurements was obtained. Our work represents the first attempt to tailor the properties of ferroelectric ceramics via varying the porosity from the viewpoint of application.     

Effects of porosity on ferroelectric properties of Pb(Zr0.2Ti0.8)O3 films

The sol-gel deposition method has been successfully applied to obtain Pb(Zr_0.2Ti_0.8)O₃ thin films on platinized silicon wafers. Addition of different amounts (7-15 wt.%) of organic macromolecular polyvinylpyrrolidone in the precursor solution prior to spin coating proves to be an excellent method for obtaining porous films. The crystal structure of as deposited films was analyzed by X-ray diffraction. The porous films show perovskite phase after annealing at 650 °C. The surface morphology has been studied by Atomic Force Microscopy and Scanning Electron Microscopy. The surface profile indicates a roughness of the film of 5 nm and no microcracks on the surface. The ferroelectric behavior was proved for each film, by hysteresis loops and by the “butterfly” shape of the capacitance-voltage characteristics. The remnant polarization and the coercive field decrease while the amount of added PVP increases.     

Electric response of Pb0.99[(Zr0.90Sn0.10)0.968Ti0.032]0.98Nb0.02O3 ceramics to the shock-wave-induced ferroelectric-to-antiferroelectric phase transition

Shock-wave-enforced ferroelectric (FE)-to-antiferroelectric (AFE) phase transition releases a large electrical polarization, having application in pulse power technology. In the present work, the depoling currents under shock wave compression were investigated in Pb_0.99[(Zr_0.90Sn_0.10)_0.968Ti_0.032]_0.98Nb_0.02O₃ (PZST) ceramics with composition close to the FE/AFE phase boundary. Shock wave was generated by gas-gun and propagated in a direction perpendicular to the remanent polarization. It was found that the shock pressure promoted the phase transition under the short-circuit condition. The shock pressure dependence of the released charge was associated with the evolution of FE-to-AFE phase transition. The onset of phase transition was about 0.40 GPa and complete transformation occurred at 1.23 GPa. However, the released charge decreased with increasing load resistance. The reason may be that the electric field suppresses the phase transition in uncompressed zone and/or shock induces conductivity in compressed zone. Results lay the foundation for application of PZST ceramics in shock-activated power supply.     

Effect of phosphorus addition on the sintering and dielectric properties of Pb(Zr0.52Ti0.48)O3

It has been found that the sintering temperature of piezoelectric Pb(Zr_0.52Ti_0.48)O₃ (PZT) can be reduced by phosphorus addition without compromising the dielectric properties. A sintered density of 98.6% of the theoretical density was obtained for 2 wt.% P₂O₅ addition after sintering at 1050 °C for 4 h. The P₂O₅ addition, either above or below 2 wt.%, showed an inferior densification. Coincidentally, the P₂O₅ addition gave rise to a lower lead loss, and the dielectric constant showed a peak at 1 wt.% P₂O₅ addition.     

Ferroelectric, dielectric and piezoelectric properties of Pb1?xCex(Zr0.60Ti0.40)O3, 0?≤?x?≤?0.08

The ferroelectric, dielectric and piezoelectric properties of compositions Pb_1−x Ce _x (Zr_0.60Ti_0.40)O₃, (x = 0.0, 0.01, 0.02, 0.04, 0.06 and 0.08) are studied. The above compositions are prepared from their constituent oxides, calcined at 900 °C for 4 h and various phases present are characterized by X-ray diffraction (XRD) technique. The above powders are uniaxially pressed into circular compacts, sintered at 1,250 °C for 2 h, electroded, poled at 2 kV/mm D.C. voltage and their electrical properties are measured. The XRD analysis shows the presence of rhombohedral phase up to 2 mol% ceria while tetragonal phase found at higher concentrations. It is observed that the ferroelectric, dielectric and piezoelectric properties increase with the addition of ceria with a maximum at 2 mol% and then decreases. The higher piezo properties associated with low ceria concentration are attributed to rhombohedral phase.