Department of Pure and Applied Physics, Guru Ghasidas Vishwavidyalaya, Bilaspur, 495009, India.
UGC-DAE CSR, University Campus, Khandwa Road, Indore, 452001, India.
Spectrochim Acta A Mol Biomol Spectrosc. 2020 Feb 15;227:117668. doi: 10.1016/j.saa.2019.117668. Epub 2019 Oct 21.
The present manuscript reports vibrational spectra and optical studies of polycrystalline FeCrVO solid solutions through FT-IR spectroscopy augmented with a group theory (G.T.) analysis and UV-Visible DRS spectroscopy. Full set of IR and Raman modes are determined by G. T. for various crystal symmetries in FeVO-CrVO solid solutions where Triclinic, Monoclinic and Orthorhombic structures evolve with increasing Cr concentration. Experimentally obtained vibrational modes support the structural phase transitions and confirm formation of continuous solid solutions in FeCrVO. The Diffuse Reflectance Spectra (DRS) of FeCrVO depicts the electronic structure and different optical transitions due to absorption of photon energy. The d-d transitions are manifested for all compounds in terms of crystal field stabilization energy (CFSE) caused by distorted lattice sites. The band gap energy of FeCrVO is calculated using Tauc formula. It shows a red shift initially within triclinic structure then blue shift with the increase of Cr concentration. Urbach energy (E) tails in the spectra show the electronic structural disorder in FeCrVO due to impurity energy levels of Cr ions within band gap region. It is observed that E decreases with the doping concentration due to the increase in crystal symmetry corresponding to the structural phase transitions in FeCrVO.
本手稿报告了通过傅里叶变换红外光谱（FT-IR）光谱学与群论（G.T.）分析和紫外可见漫反射光谱（UV-Visible DRS）对多晶 FeCrVO 固溶体的振动光谱和光学研究。对于 FeVO-CrVO 固溶体中的各种晶体对称性，通过 G.T. 确定了完整的红外和拉曼模式，其中随着 Cr 浓度的增加，出现了三斜晶系、单斜晶系和正交晶系结构。实验获得的振动模式支持结构相变，并证实了 FeCrVO 中形成了连续固溶体。FeCrVO 的漫反射光谱（DRS）描绘了电子结构和由于光子能量吸收而产生的不同光学跃迁。由于扭曲的晶格位置引起的晶场稳定化能（CFSE），所有化合物都表现出 d-d 跃迁。使用 Tauc 公式计算了 FeCrVO 的能带隙能量。它在最初的三斜晶系结构中表现出红移，然后随着 Cr 浓度的增加表现出蓝移。光谱中的 Urbach 能量（E）尾部显示了 FeCrVO 中的电子结构无序，这是由于 Cr 离子在能带隙区域的杂质能级引起的。观察到由于掺杂浓度的增加导致晶体对称性增加，从而导致 FeCrVO 中的结构相变，E 减小。
