共查询到19条相似文献,搜索用时 93 毫秒
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钛酸锶钡精细结构的理论计算 总被引:3,自引:2,他引:1
在广义梯度近似(GGA)下,利用超软赝势平面波方法计算了不同Ba/Sr摩尔比BaxSr1-xTiO3(BST)的总能量,确定了BST的精细结构.结果表明,在钛酸锶晶体中,随着Ba的掺入,晶胞体积膨胀,c/a比值增大,有利于晶体结构中正负离子的分离和自发极化的产生.如在四方相Ba0.8Sr0.2TiO3中,Ti离子沿[001]方向发生了0.008 nm的偏心位移,从而表现出BST的铁电性. 相似文献
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《中国光学与应用光学文摘》2005,(1)
O484.1 2005010406 R.F.溅射Ba0.5Se0.5TiO3/RuO2薄膜及其介电特性研究= Dielectric propertics of sputtered Ba0.5 Sr0.5 TiO3 thin film on RuO2 bottom electrode[刊,中]/张柏顺(湖北大学物理学与电子技术学院.湖北.武汉(430062)),章天金…∥光电子技术与信息,-2004,17(2).-19-22 用R.F.磁控溅射法在p-Si(100)衬底上沉积Ba0.5 Sr0.5TiO3/RuO2异质结,BST薄膜的晶相和表面形貌用 XRD和SEM分析,表明在衬底温度为550℃时。薄膜的结晶度高、表面粗糙、晶粒较大。电容器InGa/BST/RuO2的 相似文献
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采用共沉淀方法制备了稀土离子Eu3+,Dy3+,Sm3掺杂的Ca(Sr,Ba) WO4发光材料,目的是研究金属阳离子改变对稀土离子发光性质的影响.X射线衍射光谱数据表明,CaWO4、SrWO4、BaWO4都是四方晶系I41/a(88)结构,随着阳离子半径增大,衍射峰向小角移动.不同温度制备的BaWO4样品X射线衍射光谱数据表明,温度较低时制备的晶体样品X射线衍射峰较宽;当制备温度升高后,晶体样品X射线衍射峰宽变窄.样品的SEM照片表明,低温制备的样品晶粒尺寸较小,约为100~300 nm;高温制备样品晶粒尺寸较大,约为2~6 μm.测试了Eu3+,Dy3+,sm3+掺杂的Ca( Sr,Ba) WO4发光材料的激发和发射光谱.计算了Eu3+掺杂的Ca(sr,Ba) WO.的J-O强度参数Ωλ(λ=2,4),Ω2值随着阳离子半径增大迅速减小,经分析它是导致Eu3+掺杂的Ca(Sr,Ba) WO4的发射强度随着阳离子半径增大迅速减弱的原因.然而Sm3+掺杂的SrWO4其他两种晶体相比,其发射强度反而增强.根据激发光谱和文献报道,我们认为可能是由于钨酸根离子与稀土离子的能量传递引起的.从Dy3+,Sm3+掺杂的Ca(Sr,Ba)WO4的发射光谱可以看到,随着阳离子半径增大发射峰蓝移,发射峰的Stark劈裂减弱.我们用位形坐标图解释了这一现象产生的原因. 相似文献
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本文采用2-辛酸钡(Ba(C8H15O2)2)和3-甲基丁基醋酸盐(CH3COOC2H4CH(CH3)2-)为基的特殊前驱体溶液,在硅和石英基片上低温制备Ba0.7Sr0.3TiO3 (BST0.7)薄膜.性能测试结果表明,厚度约为214 nm的非晶BST0.7薄膜的光学带隙能和折射率分别为4.27 eV和n=1.94.薄膜在可见光和近红外区域的消光系数远远低于多晶BST薄膜,约为10-3数量级.激发波长为450 nm时,在室温环境下非晶BST0.7薄膜在波长520—610 nm处发出强烈的可见光,峰值为540—570 nm,而结晶态的BST0.7薄膜则无发光现象.
关键词:
钛酸锶钡
非晶薄膜
金属有机分解法
光学性能 相似文献
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用水溶液生长晶体的方法生长出了不同掺杂的Sr(NO3)2晶体.用电子探针研究了杂质在晶体中的分布情况.结果表明,杂质在晶体中存在扇形分凝,其中Ba在{100}扇形区的含量大于{111}扇形区,而Pb的分凝情况相反,在{111}扇形区的含量大于{100}扇形区.用高分辨X射线衍射摇摆曲线技术研究了纯的、掺Ba的和掺Pb的Sr(NO3)2晶体的完整性情况,并用X射线衍射动力学理论计算了完整Sr(NO3
关键词:
高分辨X射线衍射
杂质
水溶液晶体生长 相似文献
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First-Principles Investigations of Pb_(0.5)Ba_(0.5)TiO_3 Alloys Based on Structure Predictions 下载免费PDF全文
《中国物理快报》2016,(4)
Crystal structure predictions of Pb_(0.5)Ba_(0.5)TiO_3 alloys under different pressures are performed based on the particle swarming optimization algorithm.The predicted stable ground-state and high-pressure phases are tetragonal ferroelectric(I4mm) and cubic para-electric(Fm3m),respectively,whose structural details have not been reported.The pressure-induced colossal enhancements in piezoelectric response are associated with the mechanical and dynamical instabilities instead of polarization rotation.The band gap of the tetragonal phase is indirect and that of the cubic phase is always direct.As pressure increases,the alloy displays the similar band-gap behaviors to PbTiO_3,while different from BaTiO_3,which is attributed to the different orbital contributions to the valence bands.Our calculated results are in good agreement with the available data. 相似文献
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Magnetoelectric effects in multiferroic Y-type hexaferrites Ba(0.3)Sr(1.7)CoxMg(2-x)Fe(12)O(22) 下载免费PDF全文
Y-type hexaferrites with tunable conical magnetic structures are promising single-phase multiferroics that exhibit large magnetoelectric effects. We have investigated the influence of Co substitution on the magnetoelectric properties in the Y-type hexaferrites Ba(0.3)Sr(1.7)CoxMg(2-x)Fe(12)O(22)(x = 0.0, 0.4, 1.0, 1.6). The spin-induced electric polarization can be reversed by applying a low magnetic field for all the samples. The magnetoelectric phase diagrams of BaBa(0.3)Sr(1.7)CoxMg(2-x)Fe(12)O(22) are obtained based on the measurements of magnetic field dependence of dielectric constant at selected temperatures. It is found that the substitution of Co ions can preserve the ferroelectric phase up to a higher temperature, and thus is beneficial for achieving single-phase multiferroics at room temperature. 相似文献
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A. S. Anokhin A. G. Razumnaya Yu. I. Yuzyuk Yu. I. Golovko V. M. Mukhortov 《Physics of the Solid State》2016,58(10):2027-2034
A comparative study of the lattice dynamic upon phase transitions in a polycrystalline Ba0.8Sr0.2TiO3 (BST) film on a Pt substrate and in epitaxial BST films grown on various sections of an MgO substrate has been performed by Raman spectroscopy. It has been found that different sequences of phase transitions take place in these films. The BST/Pt films demonstrate the same sequence of phase transitions that is observed in the bulk ceramics. The hardening of a soft mode in BST/(001)MgO and BST/Pt films shows that the transition from the tetragonal ferroelectric phase to the paraelectric phase has features of the displacement-type phase transition and also the order–disorder phase transition. When approaching the ferroelectric transition temperature, the soft mode in the BST/(111)MgO film is softened, following the Cockran law, which indicates the displacement-type phase transition. 相似文献
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High pressure Raman spectroscopy and x-ray diffraction measurements have been carried out on Pb(1-x)Ca(x)TiO(3) (x = 0.10 and 0.30). Using high pressure Raman spectroscopic data, it is observed that the phonon instability responsible for the ferroelectric phase reappears in the paraelectric phase after a critical pressure. The observed critical pressures in the Ca(2+) doped PbTiO(3) system are much lower than the unique pressures suggested for PbTiO(3) based materials. A suitable explanation is given to explain this lowering of critical pressure. It is also shown that the ferroelectric phase which stabilizes in the paraelectric phase has a tetragonal symmetry with space group I4cm. 相似文献
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我们自行研制了具有三级差分气路可以在高气压下工作的RHEED系统(High-pressure RHEED),并利用本系统实时监测了(001)SrTiO3基片上SrTiO3:Nb、Ba0.5Sr0.5TiO3、YBa2Cu3O7单层薄膜,及Ba0.5Sr0.5TiO3/SrTiO3:Nb双层膜的生长过程.研究结果表明当镀膜室氧压高达21Pa时该系统仍然可以正常工作,并且能够获取较清晰的衍射图样.通过分析衍射图样我们发现,所有这些薄膜都是外延生长且晶体质量良好,但薄膜生长模式及表面平整度受沉积条件影响较大.在真空下薄膜基本上以层状模式生长,具备纳米级光滑的表面,且其表面平整度并不因膜厚的改变而变化;而在10Pa量级氧压下薄膜更倾向于以岛状模式生长,膜表面平整度较差,并且随膜厚的增加粗糙度上升.此外对多层薄膜而言,底层薄膜的表面和结构直接影响到顶层薄膜的质量和品质. 相似文献
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采用高温固相反应按化学式Sr4-xCaxAl14O25:Eu2+,Dy3+(x=0,0.8,1.6,2.4,3.2,4)配比原料,合成长余辉发光材料.X射线衍射分析表明当x2.4时,产物物相均为Sr4Al14O25正交结构;当x2.4时,产物物相转变为CaAl4O7单斜结构.对掺Ca量不同,但结构仍保持Sr4Al14O25的样品采用360nm激光照射,发射光谱表明样品发光均由以Eu2+为发光中心的电子4f65d→4f7跃迁所致,并且随着Ca掺入量的增加,样品发射光谱峰位逐渐蓝移.这是由于Ca2+取代Sr2+位置后,导致晶格收缩,影响Eu2+的5d能级劈裂情况,从而影响电子4f65d→4f7跃迁.余辉衰减检测和热释光谱分析发现,不同Ca掺入量的样品余辉衰减快慢不同,是由于其中存在的陷阱能级深度不同,且陷阱能级越深,其余辉时间越长. 相似文献
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分析并讨论了La_(1.6-x)Nd_(0.4)Sr_x CuO_4系列单相性样品(x=0.08~0.25)的晶体结构和超导电性。结果表明,晶体结构随着Sr掺杂量的变化规律与La_(2-x)Sr_x CuO_4系列相似。超导电性方面,La_(1.6-x)Nd_(0.4)Sr_x CuO_4系列超导转变温度均远小于相应的La_(2-x)Sr_xCuO_4系列组分。同La_(1.875)Ba_(0.125)CuO_4相似,La_(1.48)Nd_(0.4)Sr_(0.12)CuO_4处出现显著的极小值8K但高于La_(1.875)Ba_(0.125)CuO_4。La_(1.6-x)Nd_(0.4)Sr_x CuO_4系列的超导电性明显与La_(2-x)Sr_x CuO_4系列有着不同的特性,虽然同La_(2-x) Ba_xCuO_4系列相似但仍有区别。我们从其晶体结构的反常变化的角度对La_(1.6-x)Nd_(0.4)Sr_x CuO_4系列反常的超导电性做了初步的解释。 相似文献
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《中国物理 B》2021,30(7):78401-078401
The synapse of human brain neurons is not only the transmission channel of information, but also the basic unit of human brain learning and information storing. The artificial synapse is constructed based on the Sr_(0.97)Ba_(0.03) TiO_(3-x)(SBT) memristor, which realizes the short-term and long-term plasticity of the synapse. The experiential learning and non-associative learning behavior in accordance with human cognitive rules are realized by using the SBT-memristor-based synapse. The process of synaptic habituation and sensitization is analyzed. This study provides insightful guidance for realization of artificial synapse and the development of artificial neural network. 相似文献
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《中国物理快报》2017,(3)
The Sr_(0.95)Ba_(0.05)TiO_3 (SBT)nanometer film is prepared on the commercially available Pt/TiO_2/SiO_2/Si substrate by radio-frequency magnetron sputtering.The x-ray diffraction pattern and the scanning electron microscope image of the cross-sectional profile of the SBT nanometer film are depicted.The memristive mechanism is inferred.The mathematical model M(q)= 12.3656-267.4038|q(t)| is calculated,where M(q)denotes the memristance depending on the quantity of electric charge,and q(t)denotes the quantity of electric charge depending on the time.The theoretical I-V characteristics of the SBT nanometer film are obtained by the mathematical model.The results show that the theoretical I-V characteristics are consistent with the measured I-V characteristics.Moreover,the mathematical model could guide the research on applications of the memristor. 相似文献