Preparation and photophysical properties of some oxides in Ca-Bi-O system
Preparation and photophysical properties of some oxides in Ca-Bi-O system
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DOI：
10.1016/j.jallcom.2007.01.096
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发表时间：
2008-05
影响因子：
6.2
通讯作者：
Wenjun Luo;Junwang Tang;Z. Zou;Jinhua Ye
中科院分区：
文献类型：
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作者：
Wenjun Luo;Junwang Tang;Z. Zou;Jinhua Ye
采用传统的固相反应法制备了四种化学计量比的稳定相Ca 6 Bi 6 O 15、Ca 4 Bi 6 O 13、CaBi 2 O 4和Ca 5 Bi 14 O 26。研究了反应过程的细节，并在获得纯相之前通过X射线衍射鉴定了不同的中间产物。在这四个相中，Bi的价态均为+3价，Bi ~（3+）的孤对电子导致了Bi-O片状结构的形成。讨论了不同配位数和键长的Bi-O多面体。对四种样品的光学性质进行了研究。由吸收光谱估算出Ca 6 Bi 6 O 15、CaBi 2 O 4、Ca 4 Bi 6 O 13和Ca 5 Bi 14 O26的禁带宽度分别为3.34、3.08、2.76和2.60eV，它们都是直接跃迁半导体。此外，还研究了Ca 6 Bi 6 O 15、Ca 4 Bi 6 O 13和CaBi 2 O 4的拉曼光谱，结果表明，Ca的引入使晶体中出现了一些高频声子模（拉曼位移大于450 cm-1）。
Four stable phases with stoichiometric molar ratio, Ca6Bi6O15, Ca4Bi6O13, CaBi2O4and Ca5Bi14O26have been prepared by conventional solid-state reaction method. The details of the reaction processes were investigated and the different intermediate products were identified by X-ray diffraction before the pure phases were obtained. In the four phases the valence of Bi was +3 and the lone-pair electrons of Bi3+led to the formation of the Bi–O sheet structures. Bi–O polyhedrons with different coordination numbers and bond lengths were discussed. The optical properties of the four samples were also investigated. The band gaps of Ca6Bi6O15, CaBi2O4, Ca4Bi6O13and Ca5Bi14O26were estimated from the absorption spectra as 3.34, 3.08, 2.76 and 2.60eV, respectively, and they were all direct transition semiconductors. Moreover, the Raman spectra of Ca6Bi6O15, Ca4Bi6O13and CaBi2O4were also investigated and the results suggested that some high frequency phonon modes (Raman shift more than 450cm−1) appeared in the crystals with Ca being introduced into the three complex oxides.