共查询到13条相似文献,搜索用时 93 毫秒
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研究了室温下铌酸钙钡单晶的光学性质。分别用分光光度计和椭偏光谱仪测量了铌酸钙钡晶体的透射率和折射率随波长的变化关系,结果表明铌酸钙钡晶体具有正常色散关系,且寻常光折射率‰大于异常光折射率ne,说明该晶体为负的单轴晶。折射率之差在短波区达到0.12。透射率光谱显示该晶体在400~900nm波段是透明的。根据透射率计算了该波段晶体的吸收系数以及它的平方根。通过对该曲线的研究,发现铌酸钙钡晶体吸收边以下对应的跃迁为间接跃迁,计算出间接跃迁的禁带宽度E为2.94eV以及声子能量E为0.17eV。此外,通过改变系统光路中偏振片的透振方向,获得了寻常光和异常光的透射率,并进一步计算了它们的吸收系数。 相似文献
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Ca0.28Ba0.72Nb2O6(CBN28)晶体是一种新型的铁电材料,对其电光、压电、热电和光折变等性能的研究引起广泛的兴趣。X射线研究表明,Ca0.25Ba0.75Nb2O6(CBN25)结构上类似于四方钨青铜(TTB)晶体Sr0.5Ba0.5Nb2O6(SBN)。TTB晶体骨架由Nb-O八面体共顶点相连而成,沿c方向形成三角、四方和五角通道,不同有效半径的掺杂离子选择性地占据不同的通道。 相似文献
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锶铜氧超导化合物Sr2CuO3+x有无公度调制结构,Zhang H等人把它当作52a×52a的超结构,对高分辨电子显微像作了平均处理,建立了公度调制近似下的结构模型。本文用高分辨电子显微像解卷处理方法研究了Sr2CuO3+x的无公度调制结构。图1a、b分别为Sr2CuO3+x[001]和[010]电子衍射花样,强衍射斑为主衍射,每个主衍射的周围有卫星衍射,呈二维分布,反映出二维无公度调制结构。根据主衍射测得基本结构属四方晶系,空间群I/4mmm,晶胞参数a0=3·79和c0=12·45。两个调制波矢分别为q1≈0·1966a*+0·1924b*,q2≈-0·1962a*+0·1898b*,调制波矢的方向略… 相似文献
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研究了PbO3-CuV2O6(PBC)玻璃对(Pb,Ca,La)(Fe,Nb)O3(PCLFN)陶瓷微波介电性能的影响.当纯PCLFN陶瓷在1150℃烧结,介电常数εr=103,品质因数与频率之积Qf=5640 GHz,频率温度系数τf=7.1×10-6/℃.PBC玻璃添加剂能降低PCLFN陶瓷的烧结温度到1 050℃左右,同时能保持良好的介电性能.随着PBC玻璃添加量的质量分数从1.0%增加2.0%,陶瓷的Qf值减小.掺杂ω(PBC)=1%玻璃、在1 050℃烧结的陶瓷样品,能获得良好的微波介电性能为Qf=5 392 GHz,τf=8.18×10-6/℃,εr=101. 相似文献
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Ba6-3xNd8+2xTi18O54晶体结构与微波介电性能的研究 总被引:1,自引:1,他引:0
采用纳米Nd2O3以较低温度烧结出性能优良的Ba6-3xNd8 2xTi18O54(BNT)微波介质陶瓷。以X-射线衍射法测定了BNT陶瓷粉末的室温点阵常数,确定其空间群为Pbam。分析了BNT晶格结构随配比x的变化情况,与Ba6-3xSm8 2xTi18O54(BST)、Ba6-3xEu8 2xTi18O54(BET)进行比较,结果表明各离子在ab晶面内的分布对Ba6-3xR8 2xTi18O54(BRT)微波介电性能的影响较大。给出了BRT介电常数和品质因数变化的可能解释,即BRT因配比x及稀土元素的不同而产生晶格变化所致。 相似文献
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以Ba(Zn1/3Nb2/3)O3和BaWO4复合的方式,利用固相合成法,制备了(1-x)Ba(Zn1/3Nb2/3)O3-xBaWO4复合陶瓷(x=0.1-0.4),XRD表明上述两相能在烧结样品中共存。当x=0.3-0.4,在1 225℃烧结时,可以获得近零温度系数的性能优异的微波介质陶瓷,其介电性能为:εr=27.4-24.0,Q×f=53 800-65 300 GHz,τf=5.0--2.1 ppm/℃。 相似文献
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采用溶胶-凝胶(Sol-Gel)法成功制备出Ba6-3xEu8 2xTi18O54(BET,x=2/3)微粉,并利用此微粉烧结出成相良好的BET微波介电陶瓷。用X-射线衍射(XRD)法测定了BET粉末室温点阵常数,确定BET室温相为正交结构(空间群为Pbam)并指标化其衍射线,给出了BET粉末的多晶XRD数据。用X-射线光电子能谱(XPS)法测定了BET中Eu离子4d电子的结合能为135 eV,确定Eu离子为 3价、样品为充分氧化的BET陶瓷。 相似文献
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Rare-earth-modified ferroelectric crystals with the formula (Sr1−xBax)1− 3y/2 RyNb22O6, where R = La, Nd, Sm, Gd, and Lu, have Been prepared and studied. When R = La, Nd, x ≃ .5 and y = 0.02, the modified material,
at room temperature, exhibited twice the pyroelectric coefficient and four times the dielectric constant of the unmodified
Sr1−xBaxNb2O6 (x ≃ .5). Curie temperatures decreased, dielectric constants increased, while loss factor and detector signal-to-noise ratios
remained nearly the same with the addition of rare earth doping. The calculated response based on the measured properties
agree with the measured response of actual detectors. These properties suggested that the modified SBN are good materials
for small element or array pyroelectric infrared detector applications. 相似文献
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Direct Observation of Magnetic Bubble Lattices and Magnetoelastic Effects in van der Waals Cr2Ge2Te6
Arthur R. C. McCray Yue Li Eric Qian Yi Li Wei Wang Zhengjie Huang Xuedan Ma Yuzi Liu Duck Young Chung Mercouri G. Kanatzidis Amanda K. Petford-Long Charudatta Phatak 《Advanced functional materials》2023,33(26):2214203
Ferromagnetic van der Waals (vdW) materials are of large current interest for the fundamental study of low-dimensional magnetism and for potential applications in multilayer heterostructures. Cr2Ge2Te6 (CGT) is particularly exciting because it is a ferromagnetic semiconductor with tunable electronic and magnetic properties. Controlling the magnetic domain structure of CGT is a requirement for understanding its novel interface physics and for tuning behavior for potential devices. Herein, cryo-Lorentz transmission electron microscopy is performed in the temperature range of 12–50K to directly image the magnetic domain structures in CGT. A rich phase diagram of domain structures including stripe domains, magnetic bubble lattices of mixed-chirality, and topologically-protected lattices of homochiral magnetic bubbles is observed. The types and chiralities of the bubbles can be controlled by topographical changes in the CGT flakes. Additionally, it is observed that in-plane strain and magnetoelastic coupling can align and organize both bubble lattices and stripe domains. This study provides insights into creating and controlling complex magnetic domain structures for integration into multilayer heterostructures and for future studies of 2D magnetism. 相似文献