Na0.5Bi0.5TiO3-K0.5Bi0.5TiO3系无铅压电陶瓷的极化工艺研究

主要研究了极化电场,极化时间和极化温度等工艺参数对Na0.5Bi0.5TiO3-K0.5Bi0.5TiO3系无铅压电陶瓷介电和压电性能的影响。结果表明:极化电场和极化温度对压电陶瓷的介电、压电性能影响较大,而极化时间则影响较小。适宜的极化电场是3～3.5kV/mm,极化温度70～80℃,极化时间为10～15min。     

(1-x)Na0.5 Bi0.5 TiO3-xNaNbO3系无铅压电陶瓷的机电性能

采用传统陶瓷的制备方法,制备了(1-x)Na0.5Bi0.5TiO3-xNaNbO3(r=0～0．08)压电陶瓷。X射线衍射分析表明：所研究的组成均能够形成纯钙钛矿(ABOx)型固溶体。不同频率下陶瓷材料的介电常数-温度曲线显示该体系材料具有典型的弛豫铁电体特征,且随着x的增加,其弛豫性特征愈明显。室温下陶瓷材料的饱和电滞回线表明：所研究组成均为铁电体．材料的剩余极化强度P1在x=0．02时具有最大值。检测了不同组成陶瓷的雎电性能,发现材料的压电常数d33和平面机电耦合系数Kp随着x值的增加先增加后降低,在x=0．02时．陶瓷的d33=88pC／N,Kp=0．1792,为所研究组成中的最大值．材料的介电常数εI3/ε0和介电损耗tanδ则随x值的增加而增加。     

Na0.5Bi0.5TiO3-K0.5Bi0.5TiO3系无铅压电陶瓷的制备工艺研究

利用XRD、SEM等分析技术 ,研究了Na0 .5Bi0 .5TiO3 -K0 .5Bi0 .5TiO3 系无铅压电陶瓷的合成温度 ,烧成工艺条件对陶瓷晶体结构、压电性能的影响。结果表明 ,合成温度提高有利于主晶相的形成 ,适当延长保温时间有利于材料的压电性能。该体系随着KBT含量的增加 ,烧结温度提高 ,烧结温度范围变窄。同时研究了极化工艺条件对材料压电性能的影响表明 ,提高极化电场和适当提高极化温度有利于压电性能的提高 ,但过高的温度由于受到材料高温下退极化的影响而导致材料压电性能变差     

(Na1-xKx0.5)Bi0.5TiO3-xSrTiO3-0.3Mn陶瓷的性能研究

采用固相法制备了(Na1-x Kx)0.5Bi0.5TiO3-xSrnO3-0.3Mn系无铅压电陶瓷,研究了该系统的压电性能.XRD分析表明所得陶瓷样品在室温下均为三方、四方共存的钙钛矿结构,随着sr的增加三方相减少四方相增加.该体系样品具有优异的压电性能,在sr含量为0.02时,压电常数d33、平面机电耦合系数kp和厚度机电耦合系数Kt同时达到最大值,分别为171pC·N-1、33.1%和30.5%,sr具有"软性"添加物的作用.     

Na0.5Bi0.5TiO3-BaTiO3系无铅压电陶瓷的弛豫相变特征和铁电性能

研究了(1-x)Na0.5Bi0.5TiO3-BaTiO3系无铅压电陶瓷的弛豫相变特性和铁电性能。X射线衍射分析表明：当0．06≤x≤0．10时。该体系陶瓷具有三方、四方相共存的晶体结构。通过测试材料的介电温谱分析发现：当x≥0．10时,该体系陶瓷在200℃以上具有弛豫铁电体的特征。通过测试样品在不同温度的电滞回线。认为该体系材料在一定组成范围内随温度的升高存在反铁电中间相。通过研究样品的铁电性能发现：当x=0．10时,材料的矫顽场达到极小值。     

(Na1-xKx)0.5Bi0.5TiO3系的离子挥发性研究

利用固相法制备了(Na1-xKx)0.5Bi0.5TiO3系压电陶瓷,研究其中Bi3 、Na 、K 离子的挥发对其性能的影响。研究结果表明Bi3 的挥发性对样品的性能影响较大,而Na 、K 离子相对较小。     

Na0.5Bi0.5TiO3基无铅压电陶瓷研究与应用的新进展

综述了钙钛矿结构的Na0.5Bi0.5TiO3(简称BNT)基无铅压电陶瓷的研究现状,并与其它无铅基压电陶瓷进行了对比.列举了近年来BNT 基压电陶瓷的新发展和热门体系,结合笔者承担的相关研究工作内容,总结和指出了BNT基无铅压电陶瓷新的研究思路和相关方向.     

Bi0.5Na0.5TiO3基无铅压电陶瓷的研究进展

随着经济的发展和人们环保意识的增强,无铅压电陶瓷的研究和开发越来越引起人们的重视.由于钛酸铋钠(Bi0.5Na0.5TiO3,简称为BNT)基无铅压电陶瓷具有良好的铁电性和高的剩余极化引起了广大学者的关注.本文分析了BNT基无铅压电陶瓷的研究进展,其中晶粒取向生长技术是提高其压电性能的一个重要途径.本文还介绍了一种溶剂热法制备织构化BNT基无铅压电陶瓷的方法.     

Bi0.5Na0.5TiO3基无铅压电陶瓷设计与制备研究的新进展

综述了Bi0.5Na0.5TiO3(BNW)基无铅压电陶瓷体系研究的最新进展,介绍了BNT基无铅压电陶瓷的设计方法及其制备技术.用自洽场离散变分法(self-consult charge-discrete variation-Xa,SCC-DV-Xa)等计算方法可为设计新型BNT基陶瓷提供重要的理论指导.用湿化学法,包括:溶胶-凝胶法、柠檬酸盐法、水热法等,可以合成BNT基纳米粉体,该类方法制备的BNT基粉体具有良好烧结活性,利于致密化烧结,使材料电性能得到改善.用模板晶粒生长技术可获得晶粒生长定向程度很高的BNT基压电陶瓷材料,进而提高材料在特定方向的压电性能.     

(1-x)BCZT-xKNNLN无铅压电陶瓷的结构与电性能研究

为了获得高性能无铅压电陶瓷材料,本文采用传统固相烧结反应法制备了(1-x)(Ba_0.85Ca_0.15Zr_0.08Ti_0.92)-x (K_0.5Na_0.5NbO₃-LiNbO₃)(简称(1-x)BCZT-xKNNLN)无铅压电陶瓷并系统地研究了KNN含量的增加,整体电学性能的变化。研究结果表明：制备的无铅压电陶瓷具有纯的钙钛矿结构;当KNN的含量为0.4mol时,晶粒尺寸趋于一致,致密性提高,且达到了最佳的电学性能d₃₃～315pC/N, kp～0.46,ε_r～1357,tanδ～0.025。当KNN含量超过0.4mol时,整体性能逐渐下降。     

准同型相界附近(Na1-xKx)0.5Bi0.5TiO3的制备及性能研究

利用固相法制备了（Na1-xKx）0.5Bi0.5TiO3系压电陶瓷，XRD分析表明所得陶瓷样品为纯的钙钛矿结构，其准同型相界在x=0．18～0．22之间；电子探针显微分析显示所做陶瓷样品晶粒发育良好，具有规则的外形和明显的晶界；实验所得陶瓷样品损耗tanδ最大不超过5％，最好的压电常数d33=153 pC／N，平面机电耦合系数kp=0．299，它们分别出现在x=0．22和0．20处。     

（1－x）Bi0．5（Na0．8K0．2）0．5TiO3－xKSbO3压电陶瓷的制备及性能研究

采用传统固相法制备了新型（1－x）Bi0．5（Na0．8K0．2）0．5TiO3－xKSbO3无铅压电陶瓷,利用XRD、 SEM等测试技术表征了该陶瓷的晶体结构、表面形貌、压电和介电性能。研究结果表明,在所研究的组成范围内陶瓷材料均能形成纯的钙钛矿固溶体。在室温下,当KSbO3的掺杂量为1％时,该体系表现出较好的介电性能：εr和tanδ分别为2231和0．055。     

铜掺杂对(Na0.5K0.5)NbO3无铅压电陶瓷性能的影响

采用传统固相反应法对(Na0.5K0.5)NbO3压电陶瓷进行铜掺杂改性研究。使用SEM、XRD并结合常规压电陶瓷性能测试手段对该体系的显微结构、压电性能等进行表征。研究结果表明:CuO的掺入使材料出现“硬化”现象,即材料的压电系数d33、平面机电耦合系数Kp和介电损耗tanδ下降了,机械品质因子Qm大大提高;CuO掺入量在1%mol时各项性能最佳。另外,从SEM图片中可以看出:(Na0.5K0.5)NbO3压电陶瓷材料的平均晶粒尺寸随着CuO掺入量的增加明显变大。这表明CuO有烧结助熔作用,能降低烧成温度。     

Combining effects of TiO6 octahedron rotations and random electric fields on structural and properties in Na0.5Bi0.5TiO3

The structural and dielectric properties of Na_0.5Bi_0.5TiO₃ (NBT) ceramics and crystals have been investigated and are compared to that of Pb(Zr_0.55Ti_0.45)O₃ (PZT55/45) and Pb(Mg_1/3Nb_2/3)_0.72Ti_0.28O₃ (PMNT 72/28) ceramics. X-ray diffraction (XRD) profiles for (100), (110), (111), (200), (220), and (222) (referred to cubic structure) reveal that the monoclinic structure with Cc space group exists both in the NBT single crystal and ceramics. The diffraction profile obtained with high resolution laboratory XRD for the NBT single crystal can be well described, using Cc model instead of R3c model. The dielectric constant of NBT below T_hump shows some similarity to that of PZT45/55 ceramics below 50°C in which oxygen octahedron rotations cause the frequency dispersion of the dielectric constant. The temperature-dependent dielectric constant for NBT can be deconvolved into two independent processes. The lower temperature process shows a typical relaxor characteristic and follows the Vogel-Fulcher relationship. The other process at higher temperature shows less frequency-dependent behavior. Comparing the dielectric constant of NBT with that of PZT55/45 and PMNT72/28 reveals that both oxygen octahedral rotations and random electric fields play an important role in the frequency dispersion of the dielectric constant for NBT relaxor feroelectric.     

Quenching-circumvented ergodicity in relaxor Na1/2Bi1/2TiO3-BaTiO3-K0.5Na0.5NbO3

Quenching alkaline bismuth titanates from sintering temperatures results in increased lattice distortion and consequently higher depolarization temperature. This work investigates the influence of quenching on the ergodicity of relaxor Na_1/2Bi_1/2TiO₃-BaTiO₃-K_0.5Na_0.5NbO₃. A distinct departure from ergodicity is evidenced from the increase in remanent polarization and the absence of frequency dispersion in the permittivity response of poled samples. Further, the samples exhibit enhanced negative strain upon application of electric field, indicating proclivity towards correlated polar nanoregions, corroborated by the enhanced tetragonal distortion. As a result, ergodic relaxor Na_1/2Bi_1/2TiO₃-6BaTiO₃-3K_0.5Na_0.5NbO₃ exhibits a depolarization temperature of 85°C with a 60% increase in remanent polarization and approximately a threefold increase in remanent strain upon quenching. Quenching-induced changes in the local environment of Na⁺ and Bi³⁺ cations hinder the development of ergodicity promoted by the A-site disorder. These results provide new insight into tailoring ergodicity of relaxor ferroelectrics.     

Effect of sintering temperature on the depolarization behavior of (Bi0.5Na0.5)TiO3-based ceramics

(Bi_0.5Na_0.5)TiO₃ (BNT)-based ferroelectric ceramics have drawn extensive attention because of their excellent electrical properties and interesting depolarization behavior. However, the poor thermal stability of electrical properties limits their practical application. In this work, the effect of sintering temperature (T_s) on the depolarization behavior of BNT-based ceramics was systematically investigated. It is found that the depolarization temperature T_d determined from pyroelectric measurement tends to decrease with increasing T_s, which indicates that lower T_s defers the ferroelectric-relaxor (FE-RE) phase transition. However, for the samples sintered at higher T_s (such as 1180°C), although the T_d is reduced, the thermal stability is better compared with the sample sintered at lower T_s (1100°C) because the diffuse behavior of the FE-RE phase transition is suppressed. According to these results, we propose that the thermal stability of electrical properties for BNT-based ceramics is not only related to high T_d, but also to the diffuse degree of phase transition.