铁电体尺寸对其开关特性的影响

应用铁电体极化反转的Orihara Ishibashi理论 ,讨论了圆形铁电薄膜和球形铁电体的开关电流以及开关时间对系统尺寸的依赖性。数值计算表明 ,不论是二维还是三维铁电系统 ,其铁电畴反转过程中产生的开关电流都随系统尺寸减少而下降 ,开关时间随系统尺寸减少而缩短     

N.m.r. study of the ferroelectric phase transition in a 7030mol% copolymer of vinylidene fluoride (VF2) and trifluoroethylene (TrFE)

Nuclear magnetic resonance (n.m.r.) studies of ¹⁹F nuclei in a $\text{70}\text{30}\text{mol}\text{\%}$ random copolymer of vinylidene fluoride and trifluoroethylene were performed at 9.14 MHz and 20.0 MHz. The free induction decays (FIDs) were analysed in terms of two T₂ components attributed to the amorphous and crystalline portions of the polymer. The changes in crystallinity as well as the effects of the ferroelectric transition were observed during cycles of heating and cooling between 20°C and 140°C. The crystalline component of the FID lengthens by a factor of 2 at 100°C on heating and decreases by this factor at 60°C on cooling, thus exhibiting the thermal hysteresis of this ferroelectric transition. The spin-lattice relaxation was also investigated. From measurements at 9.14 MHz the observed longitudinal relaxation time T₁ appears to be dominated by the dynamics of the amorphous phase and exhibits no anomaly through the phase transition. However, from measurements at 20 MHz, well defined minima of T₁ were observed, which are associated with the ferroelectric transition (especially after repeated annealing of the samples). Results are discussed in terms of the crystalline phase structure, which appears dynamically disordered above the ferroelectric phase transition. An analogy is considered with the plastic phase transitions encountered in molecular crystals.     

脉冲激光沉积SrBi2Ta2O9铁电薄膜电容特性研究

用ＰＬＤ方法成功地制备了ＳＢＴ铁电薄膜，并制作成Ｐｔ／ＳＢＴ／Ｐｔ薄膜电容器。ＳＢＴ薄膜的晶面取向以（００８）和（１１５）为主。在５Ｖ电压下，极化反转，并且得到较饱和的电滞回线，剩余极化强度和矫顽电场分别为８４μＣ／ｃｍ２和５７ｋｖ／ｃｍ。ＩＶ特性测试显示两个对称的双稳峰，并得到零电压下，面积为３１４×１０４μｍ２，厚度为０３５μｍ的电容器，电容约为５６０ｐＦ，介电常数约为６００。疲劳测试表明Ｐｔ／ＳＢＴ／Ｐｔ具有优良的抗疲劳特性。     

Electroclinic measurement of the coefficients of Landau expansion of some ferroelectric liquid crystals

The electroclinic effect in the smectic A phase of ferroelectric liquid crystals is a sensitive probe for measuring the soft mode response near the A-C* transition point. It is possible to evaluate several coefficients of the Landau theory describing the A-C* transition by simultaneously measuring the frequency dependence of both the optical signal and the current through the sample. We have made such measurements on a couple of homologous series [2S,3S]-4′-(2-chloro-3-methyl pentanoyloxy) phenyl-trans-4″-n alkoxy cinnamates synthesized in our labortory. The results show that the Landau meanfield theory is adequate to describe the A-C* phase transition in these compounds. Presented at the 15th International Liquid Crystal Conference, Budapest, 3–8 July 1994.     

驻极体声传感器及其储电材料的现状

综述了驻极体声传感器及其储电材料近年来的迅猛发展。传统的FEP(tetrafluoroethylene—hexa—fluoropropylene copolymer)极体电容式声传感器及以铁电聚合物PVDF(poly vinylidene fluoride)家族为芯片的声传感器和超声抉能器仍焕发着青春活力。Si基微型驻极体声传感器的理论和实验研究已经日趋成熟，而用空间电荷型多孔聚合物驻极体压电薄膜为芯片可望研制出新一代声电和电声传感器、压力传感器和驱动器。     

热分解法制备钛酸铅镧薄膜及其电性能研究

本文研究了用金属有机物热发解法制备ＰＬＴ８薄膜的工艺过程和基片对薄膜结构的影响，并且给出了铁电性能的测量结果。     

Dielectric behaviour of glasses and glass ceramics in the system BaO-PbO-TiO2-B2O3-SiO2

Glasses with varying molar ratios of PbO/BaO in the system BaO-PbO-TiO₂-B₂O₃-SiO₂ were prepared keeping (BaO + PbO)/TiO₂ ratio equal to one. The glasses were ceramized by two-stage heat treatment. X-ray diffraction indicates that PbTiO₃ crystallizes in lead-rich glasses while BaTiO₃ precipitates in barium-rich compositions. Solid solution (Ba, Pb)TiO₃ does not seem to crystallize over the entire range of compositions. Simultaneous presence of PbO and BaO in the initial glass composition reduces the yield of ferroelectric phase. Dielectric properties have been interpreted in terms of microstructural features.     

铁电晶体TGS的快速生长

报道了TGS晶体的溶液状态及其快速生长的实验结果。发现了pH为2.52的溶液是实现快速生长的最佳溶液,利用快速旋转叶片来加速溶液对流,对于截面积为40mm×40 mm的(010)面,其生长速度达到了5mm/d,对快速生长的TGS晶体的性能研究表明:其热电和介电性能也发生了一些变化。     

掺Tb3+钛酸铅粉末的制备和结晶行为

采用溶胶喂胶法制备了Tb^3 掺杂钛酸铅(PbTiO3，PT)超细粉末，分别用差热分析、透射电子显微镜、X射线衍射仪对其相结构、形貌特性以及晶粒粒径等进行了分析测试。结果表明：这种粉末在约600℃热处理温度下，由非晶基体转变形成钙钛矿相的过程已逐步完成，其晶粒平均尺寸约为18nm，比未掺Tb抖的PT粉末中的钙钛矿晶粒尺寸略小。形成的钙钛矿结构中，Tb^3 取代Pb^2 进入晶格位置，产生阳离子空位，诱发晶格畸变，使钙钛矿相的析晶能力比相同热处理条件下未掺杂Tb^3 的PT低。另外，掺Tb^2 的PT中钙钛矿相的晶轴比c／a比未掺Tb^3 的PT中的低，这类似于产生了赝立方结构，降低了从立方相向这种四方相转化的势垒，有效地抑制了较高温下焦绿石相的产生，使掺Tb^3 的PT中焦绿石相稳定存在的温度比未掺Tb^3 的PT中低约100℃。     

钛酸钡基铁电材料的介电非线性研究

通过A位或B位掺杂改性得到的钛酸钡基铁电材料,在外加直流偏置电场作用下,具有介电常数非线性可调的优异介电性能,可以广泛地应用于压控可调陶瓷电容器和微波可调器件领域。针对钛酸钡基铁电材料的介电非线性特性,讨论了BaTiO_3基铁电材料分别在铁电相、顺电相以及相转变温度场附近的介电非线性机理和相关理论;结合笔者近年来有关介电非线性研究的实验结果和相关文献报道,综述了不同A位离子(如Sr~(2-)和Ca~(2-)等)或B位离子(如Zr~(4 )和Sn~(4-)等)掺杂的BaTiO_3基铁电材料体系的介电非线性研究现状,分别对不同物质形态(陶瓷块体、薄膜和厚膜)的BaTiO_3基铁电材料的介电非线性研究及其应用进行了对比分析;并对钛酸钡基铁电材料今后的发展趋势和研究方向进行了展望。