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首页> 外文期刊>Journal of Materials Chemistry, C. materials for optical and electronic devices >The crystal structure of visible light absorbing piezoelectric semiconductor SrNb2V2O11 revisited: high-resolution X-ray diffraction, vibrational spectroscopy and computational study
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The crystal structure of visible light absorbing piezoelectric semiconductor SrNb2V2O11 revisited: high-resolution X-ray diffraction, vibrational spectroscopy and computational study

机译：可见光吸收压电半导体SRNB2V2O11的晶体结构重新判断：高分辨率X射线衍射，振动光谱和计算研究

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Ferroelectric materials have a long-term track record of applications in electronics due to their spontaneous electric polarization. This property can be coupled with photoabsorption properties, resulting in a bulk photoelectric effect, the new on-the-edge domain for ferroelectric use. In this sense, considering the low bandgap of binary strontium-niobium ortho-vanadate SrNb2V2O11, which has recently been reported as ferroelectric, we propose here a deep experimental and computational understanding of its structural and physical properties, considered relevant for further applications. Microcrystalline SrNb2V2O11 was prepared by a conventional solid state route, proposing a synthetic pathway deduced from thermoanalytical observations and high-temperature powder X-ray diffraction. The crystal structure (space group Cc, a = 18.15415(2) angstrom, b = 5.52811(6) angstrom, c = 9.52728(1) angstrom, = 99.8033(8)degrees, Z = 2), successfully solved using high resolution powder X-ray diffraction, reveals the presence of distorted perovskite-like [Nb4V2O12] units when preparing [Nb2V2O11] sheets. By application of symmetry adapted mode analysis, the non-centrosymmetry originates from Sr atom displacements and [Nb4V2O12] unit breathing deformations, which can be explained in terms of the group-subgroup relationship. By ground state analysis of the polytypes across possible C-centered monoclinic cells, only the present experimentally based structural model (space group Cc) can be adopted, substituting the so far reported crystallographic data. The semiconducting nature of the phase, with a direct bandgap of 2.3 eV, was determined by optical absorption measurements and confirmed computationally. By coupling Raman spectroscopy and density functional perturbation theory, the dielectric properties (epsilon(riso) = 55) were accurately calculated and the observed optical phonons were fully interpreted. Finally, using the Berry phase formalism, we predicted a value of spontaneous polarization of 16.6 C cm(-2) in the absence of confident existing experimental data.
机译：铁电材料由于其自发性电极化而具有电子产品应用的长期轨道记录。该特性可以加上光吸收性能，导致散装光电效应，新的边缘域为铁电使用。从这个意义上讲，考虑到最近被报告为铁电的二元锶 - 铌醛钒酸盐钒酸盐的低带隙，我们提出了对其结构和物理性质的深度实验和计算理解，考虑了对进一步的应用。通过常规固态途径制备微晶SRNB2V2O11，提出从热分析观察结果和高温粉末X射线衍射推导的合成途径。晶体结构（空间组CC，A = 18.15415（2）埃埃赫斯特罗姆，C = 9.52728（1）埃，= 99.8033（8）度，Z = 2），使用高分辨率粉末成功解决X射线衍射，揭示在制备[NB2V2O11]片材时存在扭曲的钙钛矿样[NB4V2O12]单元的存在。通过对称性调整模式分析，非Centroosmmetry源自SR原子位移和[NB4V2O12]单元呼吸变形，其可以根据组 - 子组的关系来解释。通过对可能的C中心单斜细胞的多型分析，只能采用本实验基础的结构模型（空间组CC），以迄今为止报告的晶体学数据代替。通过光学吸收测量确定具有2.3eV的直接带隙的相的半导体性质，并计算到计算。通过耦合拉曼光谱和密度函数扰动理论，精确计算介电性质（ε（Riso）= 55），并且观察到的光学声音被完全解释。最后，使用浆果相形式主义，我们在没有自信的现有实验数据的情况下预测了16.6ccm（-2）的自发极化值。

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