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1.
Dunmin Lin Qiaoji Zheng Chenggang Xu K. W. Kwok 《Applied Physics A: Materials Science & Processing》2008,93(2):549-558
(1−x−y)Bi0.5Na0.5TiO3–xBi0.5K0.5TiO3– yBi0.5Li0.5TiO3 lead-free piezoelectric ceramics have been prepared by an ordinary sintering technique, and their structure, electrical properties,
and temperature characteristics have been studied systematically. The ceramics can be well-sintered at 1050–1150 °C. The increase
in K+ concentration decreases the grain-growth rate and promotes the formation of grains with a cubic shape, while the addition
of Li+ decreases greatly the sintering temperature and assists in the densification of BNT-based ceramics. The results of XRD diffraction
show that K+ and Li+ diffuse into the Bi0.5Na0.5TiO3 lattices to form a solid solution with a pure perovskite structure. As x increases from 0.05 to 0.50, the ceramics transform gradually from rhombohedral phase to tetragonal phase and consequently
a morphotropic phase boundary (MPB) is formed at 0.15≤x≤0.25. The concentration y of Li+ has no obvious influence on the crystal structure of the ceramics. Compared with pure Bi0.5Na0.5TiO3, the partial substitution of K+ and Li+ for Na+ lowers greatly the coercive field E
c and increases the remanent polarization P
r of the ceramics. Because of the MPB, lower E
c and large P
r, the piezoelectricity of the ceramics is improved significantly. For the ceramics with the compositions near the MPB (x=0.15–0.25 and y=0.05–0.10), the piezoelectric properties become optimum: piezoelectric coefficient d
33=147–231 pC/N and planar electromechanical coupling factor k
P=20.2–41.0%. In addition, the ceramics exhibit relaxor characteristic, which probably results from the cation disordering
in the 12-fold coordination sites. The depolarization temperature T
d shows a strong dependence on the concentration x of K+ and reaches the lowest values at the MPB. The temperature dependences of the ferroelectric and dielectric properties at high
temperatures may imply that the ceramics may contain both the polar and non-polar regions at temperatures above T
d. 相似文献
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采用固相合成工艺,制备了Bi05Ba05Fe05Ti049Nb001O3(BBFTN)热敏陶瓷,借助X射线衍射仪、扫描电子显微镜、阻温测试仪和交流阻抗谱考察其微结构、直流电阻、介电特性、阻抗和电学模量方面的电学性能. 结果表明:BBFTN材料依然为立方钙钛矿结构,平均晶粒尺寸约为10 μm,晶格常数相对于BaTiO3的晶格常数有所变大;室温电
关键词:
05Ba05Fe05Ti049Nb001O3')" href="#">Bi05Ba05Fe05Ti049Nb001O3
微结构
电学性能 相似文献
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以传统的固相反应法制备了Bi0.5Ba0.5FeO3陶瓷,并采用X射线衍射仪、扫描电子显微镜、直流阻温测试仪和交流阻抗分析仪测试了Bi0.5Ba0.5FeO3陶瓷的微结构和电性能.分析结果表明:Bi0.5Ba0.5FeO3陶瓷具有立方钙钛矿结构,颗粒尺寸约1.0 μm;在16—280 ℃范围内,Bi0.5Ba0.5FeO3陶瓷表现出明显的负温度系数热敏效应,其热敏常数、活化能分别为6490 K及0.558 eV;介电温谱揭示,在280 ℃下Bi0.5Ba0.5FeO3陶瓷材料没有出现相变行为.对于交流阻抗谱,采用3个串联的RQ(R与Q为并联)等效部件来拟合分析,拟合结果表明拟合数据与实验数据高度匹配,且这3个等效部件分别代表晶界、晶粒和晶壳的贡献.3个部件中,晶粒对陶瓷电阻阻值的影响最大,晶壳贡献次之,晶界最小,且3个部件电阻值都显示出负温度系数效应.在25—115 ℃范围内,电学模量虚部峰频与阻抗虚部峰频始终不匹配,意味着Bi0.5Ba0.5FeO3陶瓷体内部一直表现出局域导电机理.
关键词:
0.5Ba0.5FeO3陶瓷')" href="#">Bi0.5Ba0.5FeO3陶瓷
电性能
阻抗分析 相似文献
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利用脉冲激光制膜法,在多种衬底和温度条件下,系统研究了La0.5Sr0.5CoO3(LSCO)薄膜的结构和外延生长特性,在LaAlO3,SrTiO3和MgO衬底上实现了LSCO薄膜的外延生长.外延生长的薄膜具有低的电阻率和金属性导电特征.研究表明,外延生长的最佳温度范围为700—800℃,最佳衬底为LaAlO3.并着重探讨了衬底材料和淀积温度等多种因素对LSCO薄膜的生长与性
关键词: 相似文献
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BaFCl0.5Br0.5:Sm2+的荧光特性分析 总被引:4,自引:2,他引:2
本文是对无机光谱烧孔的典型材料BaFCl0.5Br0.5:Sm2+的发光动力学过程进行的探索。通过实验得到了5D2、5D1、5D0→7F0的荧光强度、荧光衰减曲线随温度的变化关系,对5D2→4f5d带的热激活、5DJ间的无辐射弛豫,5DJ→7F0的辐射跃迁等过程进行了分析。 相似文献
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在0—7GPa静压范围内测量了自发有序Ga0.5In0.5P合金的室温光致发光谱.三块样品的常压带隙能量分别比无序样品低115,92和43meV,它们的压力系数也从无序样品的92meV/GPa分别减小到75,81和83meV/GPa.用Γ-L相互作用模型可以同时解释有序合金的带隙能量的降低以及压力系数的减小.得到的Γ-L相互作用势分别为0.19,0.15和0.10eV.表明在自发有序Ga0.5In0.5P合金中存在着的 相似文献
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用扫描隧道显微镜/谱仪仔细研究了铁基超导单晶FeSe0.5Te0.5样品的表面形貌和隧道谱, 测量到了清晰的表面原子形貌和在空间比较稳定的隧道谱结构.在样品中测量的隧道谱零能态密度比较高, 说明样品里面有比较强的非弹性准粒子散射. 在正能5 mV附近有个较大的背景鼓包, 这一背景在很高温度也未消失. 空间中Se和Te集中的位置会带来高能背景的变化, 超导能隙附近谱的形状大致相同. 较强的非弹性准粒子散射破坏了超导的准粒子散射, 因此没有在二维微分电导图中发现超导准粒子相干散射的特征亮斑. 相似文献
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Na0.5K0.5NbO3是一种不含铅的新型压电材料。理解该物质在高压下的晶体结构变化,有助于深入认识并提高其材料的稳定性及压电性能。然而目前关于该物质在高压下的相结构演化过程还缺少实验研究。本工作采用基于金刚石对顶砧(DAC)的高压拉曼光谱技术,研究了Na0.5K0.5NbO3的高压拉曼光谱特性与压致相变行为。研究发现Na0.5K0.5NbO3在高压环境下由于NbO6八面体的振动模式发生改变,会依次发生正交相到四方相和四方相到立方相的可逆相变过程,其相变压力分别为4.0~5.5 GPa和5.5~6.4 GPa。 相似文献
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溶胶凝胶法制备了Na0.5Bi0.5Ti1-xMnxO3(x=0,0.02,0.04)陶瓷样品,X射线衍射(XRD)分析表明陶瓷样品均形成了单一的钙钛矿(ABO3)型结构且没有杂质相的形成.随着Mn含量的增加,XRD峰向高角度方向移动,表明Mn离子进入Na0.5Bi0.5TiO3晶格.掺杂样品均表现出室温铁磁性和铁电性.磁测量表明样品中存在复杂的磁相互作用,包括铁磁,反铁磁和顺磁相互作用.以上结果表明,通过Mn的掺杂可以使铁电材料Na0.5Bi0.5TiO3转变为多铁材料. 相似文献
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利用固相反应法制备Pr0.5Ca0.5MnO3(PCMO)靶材,并采用脉冲激光沉积法(PLD)在n型Si(111)基片上沉积PCMO外延薄膜,研究了薄膜的输运特性及薄膜与Si衬底形成异质结的整流特性.结果表明:在80—300 K温度范围内,PCMO薄膜的阻温关系符合变程跳跃模型,随着温度的升高表现出从一维到二维再到三维的转变,分析认为可能源于轨道自由度对电子输运特性的影响.PCMO/Si异质结在磁场作用下整流特性得到改善,且在正向电流方向出
关键词:
0.5Ca0.5MnO3')" href="#">Pr0.5Ca0.5MnO3
Si
整流
正磁电阻 相似文献
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本文用光致发光(PL)研究了MOCVD(金属氧化物化学气相沉积)生长的有序Ga0.5In0.5P外延层的光学性质.发现有序程度较强的Ga0.5In0.5样品的PL谱中一峰的能量随温度升高,先增大而后又减小.根据已有的报道和本文的实验结果,提出了一个有序Ga0.5In0.5P的模型,模型中将有序Ga0.5In0.5P看作阶宽随机分布的Ⅱ型多量子阱结构,能带边之下存在带尾态,并用该模型对实验结果进行了较好的解释. 相似文献
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The Si doped (Cu0.5Tl0.5)Ba2Ca2Cu3−ySiyO10−δ (y=0, 0.25, 0.5, 0.75, 1.0, 1.25) superconductor samples have been synthesized to investigate the effect of mobile carriers on the critical temperature and magnitude of diamagnetism of this family of cuprates. The Si doped samples have tetragonal structure as observed from the X-ray diffraction spectra. The c-axis length of the unit cell of (Cu0.5Tl0.5)Ba2Ca2Cu3−ySiyO10−δ was increased after the increase of Si concentration, whereas the critical temperature and the magnitude of diamagnetism have been decreased. The decrease in Tc(0) and magnitude of diamagnetism is possibly due to the deficiency of carriers in CuO2/SiO2 planes caused by the +4 state of Si atoms. However, the post-annealing of these samples in oxygen atmosphere has increased the critical temperature and the magnitude of diamagnetism. The FTIR absorption measurements of (Cu0.5Tl0.5)Ba2Ca2Cu3−ySiyO10−δ samples have shown a softening of the apical oxygen mode of the type Cu(1)OACu(2) and TlOACu(2) with increased concentration of Si in the unit cell; the softening of this mode is directly linked with the increase in the c-axis lattice parameter of the (Cu0.5Tl0.5)Ba2Ca2Cu3−ySiyO10−δ superconductor. 相似文献
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用溶胶-凝胶工艺成功制备出Bi05Na05TiO3纳米微粉,并利用此微粉烧结出高致密度的Bi05Na05TiO3陶瓷.这种新工艺制备的Bi05Na05TiO3陶瓷,其压电性能远远高于普通方法制备的陶瓷,其中压电常数d33和机电耦合系数kt分别高达102×10-12C/N和58%.同时发现,对于这种Bi05Na05TiO3陶瓷,室温时只需施加100kV/cm左右的交变电场,就可得到矩形度极好的饱和回线,得到的剩余极化Pr和矫顽场Ec分别为32μC/cm2和61kV/cm.而在100℃以上只需施加35kV/cm的极化电场就可使样品充分极化. 相似文献
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利用能量最小原理, 确定了Ca0.5Sr0.5TiO3晶体中4c位置的Ca/Sr原子对称分布, 建立了Ca0.5Sr0.5TiO3稳定的晶体结构, 在此基础上利用基于密度泛函理论第一性原理的平面波超软赝势方法, 采用局域密度近似和广义梯度近似函数, 计算了Ca0.5Sr0.5TiO3的晶格参数、弹性常数、体弹模量、剪切模量、杨氏模量、泊松比, 并基于Christoffel方程的本征值研究了平面声波的特征, 基于Cahill和Cahill-Pohl模型研究了最小热导率的特征. 计算结果表明: Ca0.5Sr0.5TiO3晶格参数和实验值很接近, 体弹模量大于剪切模量, [100], [010], [001]晶向的杨氏模量、泊松比、普适弹性常数(AU)以及杨氏模量三维图均显示了弹性各向异性; 平面声波在(010), (001)平面呈现各向异性, 在(100)平面呈现各向同性, 平面声波大小与平均横波和平均纵波的数值很接近. Cahill模型最小热导率在各平面呈现各向同性, Cahill-Pohl模型最小热导率在高温时趋于恒定. 准谐德拜模型下Ca0.5Sr0.5TiO3 晶体的摩尔热容和热膨胀系数与CaTiO3晶体的接近, 并且高温下具有稳定的热膨胀性能. 计算所得禁带宽度为2.19 eV, 导带底主要是Ti-3d与O-2p态电子贡献; 由电荷布居和电荷密度图理论证实Ca0.5Sr0.5TiO3具有稳定的Ti-O八面体结构. 相似文献
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The dielectric properties of Cu0.5Tl0.5Ba2Ca3Cu4O12−δ superconductor samples were studied at 79 and 290 K by means of capacitance (C) and conductance (G) measurements with the test frequency (f) in the range of 10 kHz to 10 MHz. A negative capacitance (NC) phenomenon has been observed, which is most likely arising due to higher Fermi level of ceramic superconductor samples than metal electrodes. Also the NC may be due to the space charge located at the multiple insulator–superconductor interfaces (grain boundaries) in the materials. The negative dielectric constant (ε′) and loss factor (tan δ) show strong dispersion at low frequencies. The lower thermal agitation at 79 K may enhance the polarizability and hence the dielectric constants (ε′ and ε″). 相似文献