排序方式: 共有23条查询结果,搜索用时 656 毫秒
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利用低压MOCVD工艺分别在(001)取向的LaAlO3,SrTiO3和重掺杂硅单晶衬底上制备PbTiO3铁电薄膜,并通过X射线衍射谱对薄膜的微结构进行分析.X射线θ-2θ扫描显示硅衬底上得到了PbTiO3多晶薄膜,另两种衬底上得到了择优取向的PbTiO3薄膜.LaAlO3衬底上的PbTiO3薄膜有a和c两个取向,也就是薄膜中存在着90°畴结构,而生长在SrTiO3衬底上的PbTiO3薄膜中只存在c方向的择优取向.由于薄膜的尺度效应,发现c轴晶格常数与块材相比均缩短.X射线的φ扫描验证了后两类薄膜的外延特性,利用同步辐射的高强度和高能量分辨率用摇摆曲线方法研究了这两种外延薄膜的品质,进一步证明了SrTiO3衬底上的PbTiO3薄膜的单畴特性.利用重掺杂的硅衬底作底电极,测量显示直接生长于硅衬底上的PbTiO3多晶薄膜具有良好的铁电性能
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Raman spectra of ceramic Sr2Bi4Ti5O18 (SBTi5) are reported to consist of four different Raman bands. Temperature-dependent spectra reveal the relationship between the lattice vibration and the material's structure. There appears a relatively large change in structure of the material at about 273K, The anharmonic potential of the material has a great influence on its phonon mode full width at half maximum (FWHM), which can be expressed by a function of temperature. Theoretical fittings of the FWHMs for the two modes at around 312 cm^-1 and 464cm^-1 indicate that the latter phonon mode is more anharmonic than the former one. 相似文献
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基于纳米尺寸下复合铁电材料和反铁磁性材料是一个探索多铁性材料有效的方法. 利用激光脉冲沉积制备出LaFeO3-YMnO3人工超晶格和掺入不同层LaFeO3, BiFeO3的Bi4Ti3O12的外延薄膜. 通过系统的X射线衍射、透射电子显微术、扫描透射电子显微术下的能量损失谱表征证明这些样品具有原子尺寸上清晰的界面和完整的层状结构. 磁性测试证明这些材料具有亚铁磁性. 特别是在0.5和1.5LaFeO3-Bi4Ti3O12中的亚铁磁性甚至能保持到室温. 就铁电性而言, 铁电性测试显示出LaFeO3-YMnO3和插入BiFeO3的Bi4Ti3O12样品中存在较大的漏电流, 而在0.5LaFeO3-Bi4Ti3O12样品中存在铁电性. 因此在0.5LaFeO3-Bi4Ti3O12中能够实现亚铁磁和铁电共存. 其次发现当掺入多层的钙钛矿(3层SrTiO3或2.5层LaFeO3)后, Bi4Ti3O12 的层状结构将出现结构失稳现象. 这些工作对于利用纳米复合开发新颖多铁性提供一些实例. 相似文献
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针对管道内低频噪声难以抑制的问题,本文基于亥姆霍兹共振腔(HR)阵列吸声板和穿孔管消声器组合,设计了一种复合式宽带消声器。首先利用有限元法仿真分析传统穿孔管消声器,发现中低频消声能力较差,通过嵌入HR阵列吸声板吸收中低频噪声。采用仿真与实验的方式研究吸声板的声学性能:在400-1000 Hz频段内的平均吸声系数达到了0.88。然后对复合式消声器进行数值模拟及3D打印阻抗管实验测试对比:复合式消声器在400-1718Hz频率范围内的平均传递损失为18.15 dB ,最终实现了管道内全频带噪声有效控制。 相似文献
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连续渐变周期的一维光子带隙结构全能反射器 总被引:20,自引:7,他引:13
采用转移矩阵法设计了一种具有连续渐变周期的一维光子带隙结构全能反射器,它在一般材料选取情况下(如TiO2/SiO2),在可见光区能达到几十甚至几百纳米量级的带隙宽度全向反射.研究表明,其带隙宽度随着周期数和渐变周期的大小改变而改变.当周期数不断增大时,带隙宽度不断增大;当渐变周期的大小在一定范围内不断增大时,带隙宽度同样不断增大.这主要是光波在各层之间的传播随着周期和渐变周期的大小不断增大而产生的相干散射和干涉效应不断增强所导致的. 相似文献
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A 2-mm-long silicon-on-insulator grating emitter with a narrow angular full width at half-maximum(FWHM) and a high sideband suppression ratio(SSR) is proposed and designed. It consists of a Si3N4/Si grating with an approximate Gaussian emission profile along the grating length, which aims to reduce the sidelobe intensity of the scanning light in the far-field, thereby improving the resolution of the longitudinal steering resolution of the light detection and ranging(lidar).... 相似文献
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Electronic structure and spin–orbit coupling in ternary transition metal chalcogenides Cu2TlX2 (X = Se,Te) 下载免费PDF全文
Ternary transition metal chalcogenides provide a rich platform to search and study intriguing electronic properties. Using angle-resolved photoemission spectroscopy and ab initio calculation, we investigate the electronic structure of Cu$_{2}$Tl$X_{2}$ ($X=\text{Se, Te}$), ternary transition metal chalcogenides with quasi-two-dimensional crystal structure. The band dispersions near the Fermi level are mainly contributed by the Te/Se p orbitals. According to our ab-initio calculation, the electronic structure changes from a semiconductor with indirect band gap in Cu$_{2}$TlSe$_{2}$ to a semimetal in Cu$_{2}$TlTe$_{2}$, suggesting a band-gap tunability with the composition of Se and Te. By comparing ARPES experimental data with the calculated results, we identify strong modulation of the band structure by spin-orbit coupling in the compounds. Our results provide a ternary platform to study and engineer the electronic properties of transition metal chalcogenides related to large spin-orbit coupling. 相似文献