锆钛酸铅镧压电陶瓷纤维的制备与性能

以锆钛酸铅镧[(Pb1-xLax)(Zr1-yTiy)O3,lead lanthanum zirconate titanate,PLZT]压电陶瓷为原料,用塑性聚合物法制备不同截面的PLZT陶瓷纤维。用X射线衍射、扫描电镜、密度测试仪、微力试验机和铁电分析仪分别测试PLZT陶瓷纤维的相结构、显微形貌、密度、力学性能和铁电性能。结果表明:PLZT陶瓷纤维为三方相钙钛矿结构,圆柱形纤维的直径和方柱形纤维的边长分别约250μm和300μm。圆柱形和方柱形纤维的最终抗拉伸强度和弹性模量分别为24.88MPa、6.90×103MPa和23.97MPa、5.71×103MPa。PLZT陶瓷纤维均具有良好的铁电性能,圆柱形纤维的饱和场强、剩余极化强度(Pr)和矫顽场(Ec)分别为10kV/mm、41.40μC/cm2和1.10kV/mm;方柱形的饱和场强、Pr及Ec分别为10kV/mm、41.68μC/cm2和1.03kV/mm。     

锆锡钛酸镧铅反铁电体陶瓷的低温烧结和储能特性

随着风电、光电等绿色能源的利用和对大功率电力电子装备需求的增加,大功率储能器件受到了广泛的关注,而具有高储能密度和高储能效率的(Pb,La)(Zr,Sn,Ti)O₃ (PLZST)反铁电体陶瓷用于超级介电储能电容器具有明显的优势。但是,受到陶瓷本身高烧结温度(1 200～1 300℃)的限制,难以适应贱金属内电极多层陶瓷电容器的应用。为了适应贱金属铜(Cu)内电极的烧结,将玻璃粉MgO–Al₂O₃–ZnO–B₂O₃–SiO₂(MAZBS)添加到(Pb_0.97La_0.02)(Zr_0.55Sn_0.41Ti_0.04)O₃(PLZST)反铁电体陶瓷中,使烧结温度低于铜内电极的熔点。研究结果表明：当添加了玻璃粉MAZBS的质量分数为0.75%时,PLZST陶瓷在较低的温度(930℃)下可以实现致密烧结,且陶瓷在室温和外加电场300 kV...     

有机钛(锆)酸酯催化法合成缩醛(酮)的研究

利用钛(锆)酸酯为催化剂,通过醛酮与醇反应,制备了14种缩醛(酮)。该法具有催化剂用量小,产率高,无设备腐蚀及环境污染等优点。     

近化学计量比LiNbO3晶体的坩埚下降法生长

报道了化学计量比LiNbO3(stoichiometric lithium niobate, SLN)晶体的坩埚下降法生长.采用一致融熔成分铌酸锂籽晶,以K2O为助熔剂,在自制的坩埚下降炉内生长SLN晶体.最高炉温控制在1 300 ℃附近,固液界面处的纵向温度梯度为40～60 ℃/cm,坩埚下降速率小于5 mm/d,在密闭的铂坩埚中,成功地生长出尺寸为25 mm×40 mm的近化学计量比铌酸锂单晶.测得晶体的Curie温度为190 ℃,利用有关公式计算出所得晶体的n(Li)/n(Li+Nb)为0.495 6,研究了熔体的析晶行为及晶体的宏观缺陷.     

锆钛酸铅镧纤维1-3压电复合材料的制备及性能

以锆钛酸铅镧[(Pb1-xLax)(Zr1-yTiy)O3,PLZTJ压电陶瓷、聚乙烯醇[(C2H4O)n]和丙三醇(C3H7O3)为原料,用塑性聚合物法制备了PLZT陶瓷纤维.通过排列PLZT陶瓷纤维,灌注环氧树脂E-51的方法制备了陶瓷相体积分数为30%的PLZT/E-51型1-3压电复合材料.用扫描电子显微镜和X射线衍射分别进行显微结构和相结构分析.结果表明:排胶、烧结后PLZT陶瓷纤维横截面直径约250μm,为三方相钙钛矿结构.1-3压电复合材料的压电常数(d33)、相对介电常数(εr)、厚度机电耦合系数(kt)、径向机电耦合系数(kp)、各项异性(kt/kp)和声阻抗(Z)分别为500×10-12 C/N,626,0.67,0.30,2.23和11.03×106 kg/(m2·s).该1-3压电复合材料的各向异性远远大于纯陶瓷的,Z显著减小,接近聚合物的水平,使l-3压电复合材料作为超声换能器材料使用时,其探测分辨率明显提高且更易找到与之匹配的背衬.     

铁电磁体Pb(Fe1/2Nb1/2)O3单晶高温熔液法生长及其结构特征研究

采用高温溶液晶体生长法,选择PbO为助熔剂,以缓慢冷却法获得过饱和度并施以温度振荡,生长出典型尺寸为3 mm×3 mm×3 mm的铁电磁体Pb(Fe1/2Nb1/2)O3单晶.用变温X射线衍射和变温Raman光谱研究了Pb(Fe1/2Nb1/2)O3单晶的结构对称性.结果表明Pb(Fe1/2Nb1/2)O3在实验的最低温度80 K到铁电相变温度383 K之间均为菱面体结构.在反铁磁相变温度Neel点以上,Pb(Fe1/2Nb1/2)O3体对角线逐渐变短,而在该温度以下,其结构没有变化.在测量的温度20～200 K范围内,Raman光谱的峰位不随温度变化,说明其结构在该温度范围内没有明显变化.实验结果将有利于进一步研究铁电磁体的形成机制.     

(Pb,La)(Zr,Sn,Ti)O3 陶瓷、锆锡钛酸铅镧/聚偏氟乙烯-三氟乙烯复合材料的介电性能

用固相烧结法,在1200℃烧结2．5h的条件下,制备了(Pb0.97La0.02)(Zr0.66Sn0.23Ti0.11)O3(PLZST)四方相陶瓷和陶瓷粉末,并将其与聚偏氟乙烯-三氟乙烯[polyvinylidene fluoride—trifluoroethylene,P(VDF-TrFE)]相复合制备了70％(体积分数)PLZST／P(VDF—TrFE)复合材料。用3～4MeV、剂量为60Mrad的电子束对PLZST陶瓷及其复合材料进行处理,测量其辐照前后的介电温谱,研究其弛豫性能的变化。结果表明：电子束辐照对PLZST陶瓷的介电温谱几乎没有影响,没有改变它的非弛豫特征;70％PLZST／P(VDF-TrFE)复合材料由于两相界面间的耦合作用产生微畴而具有弛豫特征,而辐照处理对P(VDF—TrFE)内部铁电宏畴的破坏使得其弛豫性能得到显改善,从而获得了一种良好的弛豫型复合材料。     

光学级硅酸镓镧晶体的生长初探(Ⅰ)--晶体原料、起始配比与提出量的讨论

根据制作La3Ga5SiO14(LGS)晶体电光Q开关的需要,生长了可用于制作电光Q开关的LGS晶体。根据大量晶体生长实验的结果,讨论了晶体原料纯度、来源、晶体原料起始组分配比及晶体提出量与晶体质量的关系,认为Ga2O3的纯度和来源对晶体质量的影响最大。实际生长光学应用的LGS晶体过程中,La2O3纯度为5N(或6N),而SiO2为6N。起始组分配比应选共熔点处的配比,即x(La2O3)=30．00％,x(Ga2O3)=50．65％,x(SiO2)=19．35％。考虑到生长过程中Ga2O3的挥发,Ga2O3应适当过量,n(Ga)／n(Si)范围为5．20～5．30。晶体提出量与起始组分有关,晶体提出量以50％～60％为宜。     

砷酸钛氧铷(RbTiOAsO4)晶体的性质

采用高温溶液法生长出２０ｍｍ×３６ｍｍ×５２ｍｍ透明的ＲＴＡ单晶,压电常数值的分布和熔盐腐蚀形貌均证明晶体为单畸。本文报道了ＲＴＡ晶体宽的透光范围,良好的倍频性质,低的电导率,低的介质损耗以及铁电相变、介电常数、压电常数、测试结果表明,ＲＴＡ晶体在红外光参量振荡器、光参量放大器和倍频等方面有应用前景,并且是一种优良的光电材料。     

热压烧结对锆钛酸铅镧陶瓷电卡效应的影响

探讨热压烧结工艺对PLZT(锆钛酸铅镧)陶瓷材料介电击穿性能、饱和极化强度以及电卡性能的影响。通过X射线衍射和扫描电子显微镜,分析陶瓷样品的相组成和微观结构。结果表明,热压烧结法有助于控制陶瓷晶粒的生长,提高陶瓷的致密度并增大陶瓷的介电击穿场强,从而有效提高陶瓷的电卡性能以及电卡转换效率。在328 K(55℃)与478 K(205℃)附近,分别发生低温铁电三方相到高温铁电三方相的相变(FRL-FRH)以及高温铁电三方相到立方顺电相(FRH-Pc)的相变,展现了比较好的弛豫性,在室温下达到3.6 K的绝热温变与1.8×0-7(K·m)/V的电卡转换效率,具有良好的电卡性能。     

Fatigue-Free Lead Zirconate Titanate (Pb(Zr,Ti)O3)-Based Capacitors Co-modified by Lanthanum and Lithium for Nonvolatile Memories

Pb_0.98(La_{1− x} Li _x )_0.02(Zr_0.55Ti_0.45)O₃(PLLZT with 0.1 ≤ x ≤ 0.7) thin films were sol-gel-grown on Pt(111)/Ti/SiO₂/Si substrates, employing a thin lead zirconate titanate (PZT) template layer. Films annealed at >550°C showed a highly (111)-oriented preferential growth. Typical values of the switchable remanent polarization (2 P _r) and the coercive field ( E _c) of the PLLZT/PZT/Pt film capacitor for x = 0.3 were 50 μC/cm² and 39 kV/cm, respectively, at 5 V. All the PLLZT/PZT/Pt capacitors (for 0.1 ≤ x ≤ 0.7) exhibited fatigue-free behavior up to 6.5 × 10¹⁰ switching cycles, a quite stable charge retention profile with time, and high 2 P _rvalues, all which assure their suitability for nonvolatile ferroelectric memories.     

组成对锆钛酸铅铁电薄膜电性能影响的研究进展

锆钛酸铅材料因具有优异的介电、压电和铁电性被广泛用于制作电容器、压电器件和铁电随机存储器等功能器件.本文综述了锆钛酸铅铁电薄膜材料中锆钛比、掺杂种类及掺量对其介电性和铁电性的影响,并提出了亟待解决的问题.     

Electrostrictive and Dielectric Response in Lead Magnesium Niobate–Lead Titanate (0.9PMN · 0.1PT) and Lead Lanthanum Zirconate Titanate (PLZT 9.5/65/35) under Variation of Temperature and Electric Field

In situ measurements of electrostrictive strain and effective dielectric constant for two ferroelectric relaxor materials, lead magnesium niobate–lead titanate (0.9PMN · 0.1PT) and lead lanthanum zirconate titanate (PLZT 9.5/65/35), were performed in the temperature ranges near their respective mean Curie points under the variation of applied electric field. The measurement results show that the polarization-related electrostrictive coefficients Q_ij are not constant under variation of temperature and electric field. The observed anomaly in Q_ij indicates the dynamic behavior of the existing micropolar domains and its coupling to local defect structure. The data also support the idea that at temperatures far above the mean Curie point, there is still a substantial amount of micropolar domain and the response of the relaxor materials at the experimental temperature range is from the combined contributions due to induced polarization and micropolar domain flipping.     

Crystallization of Fine, Chemically Prepared Lead Lanthanum Zirconate Titanate Powders at Low Temperature

Fine, homogeneous lead lanthanum zirconate titanate (PLZT) powder prepared by the hydrolysis of an aqueous nitrate solution with ammonia gas exhibits high reactivity when calcined. The minimum temperature for crystal formation in PLZT is 400°C. The kinetics of crystallization between 400° and 600°C are studied isothermally by XRD. The isothermal crystallization process is best fitted to a first-order equation derived for a random, nucleation-controlled system on a large number of small particles with an activation energy of 297 kJ/mol. Characterization of the powder by XRD line-broadening and BET surface-area examination in the range 400° to 500°C shows a microstructure consisting of ∼20-nm subunits agglomerated into ∼60-nm particles. Each subunit evidently generates a single nucleus, which grows within that subunit.     

Effect of Manganese Ion Diffusion on the Microstructural Evolution of Lead Lanthanum Zirconate Titanate Ceramic

Microstructural evolution of lead lanthanum zirconate titanate (PLZT) ceramics caused by diffusion of the Mn ion was observed. Specimens with layered structures were fabricated by copressing a PLZT powder (9/65/35) doped with Mn and same PLZT powder without the dopant. When the copressed specimen was sintered at 1200°C in air, the Mn ion diffused out of the doped region. The region originally containing the Mn ions was totally free of pores while all other regions remained porous. The formation of lattice vacancies, as a result of Mn diffusion, was attributed to the enhanced material transport and the resultant rapid densification.     

Phase Stability and Ferroelectric Properties of Lead Strontium Zirconate Titanate Ceramics

The effect of compositional modifications on the field-induced phase-transition behavior and dielectric properties of strontium-doped lead zirconate titanate (PZT) ceramics was studied. PZT compositions with different strontium and titanium contents, within the general formula Pb_{1– x} Sr _x (Zr_{1– y} Ti _y )O₃ and located in the tetragonal antiferroelectric (AFE) and rhombohedral ferroelectric (FE) phase fields were prepared by tape casting and sintering. X-ray diffraction and polarization measurements were used to locate compositions suitable for investigation of the field-induced AFE–FE phase transition. The results indicated that a higher Sr²⁺ content decreased the polarization and hysteresis and increased the switching field; a lower Ti⁴⁺ content decreased the polarization and increased the switching field and hysteresis. A high room-temperature dielectric constant was obtained for compositions near the phase boundary. These results suggest that a combination of both A -site and B -site modifications can be used to tailor ferroelectric properties, such as the switching field and hysteresis, of these strontium-doped PZTs displaying a field-induced AFE–FE phase transition.     

二乙醇胺辅助溶胶-凝胶法低温合成锆钛酸铅纳米粉体

以醋酸铅[Pb（CH3COO）2^-33H20]、硝酸锆[Zr（N03）4^-5H2O]和钛酸四丁酯[Ti（C4H90）4]为原料,以二乙醇胺（diethanolamine,DEA）为聚合剂．用溶胶-凝胶法制备了锆钛酸铅（PbZrxTil-x03,PZT）纳米陶瓷粉体。研究了DEA对溶胶-凝胶法合成PZT陶瓷粉体的影响...     

Fabrication of NiO Nanoparticle-Coated Lead Zirconate Titanate Powders by the Heterogeneous Precipitation Method

NiO nanoparticle-coated lead zirconate titanate (PZT) powders are successfully fabricated by the heterogeneous precipitation method using PZT, Ni(NO₃)₂·6H₂O, and NH₄HCO₃ as the starting materials. The amorphous NiCO₃·2Ni(OH)₂·2H₂O are uniformly coated on the surface of PZT particles. XRD analysis and the selected-area diffraction (SAD) pattern indicate that the amorphous coating layer is crystallized to NiO after being calcined at 400°C for 2 h. TEM images show that the NiO particles of ∼8 nm are spherical and weakly agglomerated. The thickness of the nanocrystalline NiO coating layer on the surface of PZT particle is ∼30 nm.     

Fabrication of Optically Transparent Lead Lanthanum Zirconate Titanate ((Pb,La)(Zr,Ti)O3) Ceramics by a Three-Stage-Atmosphere-Sintering Technique

An easy technique has been developed to fabricate optically transparent lanthanum-modified lead zirconate titanate (PLZT) ceramics. This technique consists of three stages: (1) sintering in an oxygen atmosphere, (2) elimination of pores in a carbon dioxide atmosphere, and (3) elimination of oxygen vacancies in an oxygen atmosphere. The carbon dioxide atmosphere enhances the diffusion of oxygen from the pores to outside the sintered body. The experimental results reveal that use of a carbon dioxide atmosphere effectively decreases residual pores and improves optical transmittance. From commercially available raw powders, an optical transmittance of 51% (wavelength of 550 nm) can be achieved for 0.7 mm thick polished PLZT9/65/35 ceramics using a carbon dioxide atmosphere, whereas the value is only 34% without a carbon dioxide atmosphere. The advantage of this technique is that PLZT ceramics having high optical quality can be obtained using conventional sintering tools.