Ab Initio and Experimental Insights on Structural, Electronic, Optical, and Magnetic Properties of Cr-Doped Bi2Ti2O7
| Autor: | Maxim I. Vlasov, I. V. Piir, A.G. Krasnov, I. R. Shein, M.S. Koroleva, Dina G. Kellerman |
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| Rok vydání: | 2019 |
| Předmět: |
Dopant
Magnetic moment 010405 organic chemistry Rietveld refinement Bismuth titanate Pyrochlore Ab initio engineering.material 010402 general chemistry 01 natural sciences 0104 chemical sciences Inorganic Chemistry chemistry.chemical_compound Paramagnetism chemistry engineering Physical chemistry Density functional theory Physical and Theoretical Chemistry |
| Zdroj: | Inorganic Chemistry. 58:9904-9915 |
| ISSN: | 1520-510X 0020-1669 |
| DOI: | 10.1021/acs.inorgchem.9b01057 |
| Popis: | Combined ab initio and experimental study of Cr doping into bismuth titanate pyrochlore was carried out for the first time. Accurate first-principles density functional theory calculations were performed considering a Hubbard U correction (DFT+U) to account for on-site Coulomb interactions of the Cr 3d states. The possibility to synthesize a novel pyrochlore-type compound with a high dopant content Bi1.5Cr0.5Ti2O7 (Bi site doping) in a fine powder state was shown via coprecipitation method, while the single-phase Bi2Ti1.5Cr0.5O7 (Ti site doping) could not be obtained. Detailed descriptions of thermostability, structural, optoelectronic, and magnetic properties of Cr-doped pyrochlores in the fine (particles size 100-300 nm) and "bulk" (1-50 μm) powder states are presented based on the well-matched results of theoretical and experimental investigations. According to the Rietveld refinement of the X-ray diffraction data, Bi1.5Cr0.5Ti2O7 compound is an A-site deficient pyrochlore (Bi1.38Cr0.30)(Ti1.84Cr0.16)O6.44 with chromium distribution between both cationic sites. Metastability of fine powder Cr-containing pyrochlore phase was revealed during long-thermal annealing, while the bulk powder sample was stable up to its melting point 1230 °C. According to the study of electronic structure and optical properties, Cr-doped pyrochlores are wide-band semiconductors with light absorption in the range of 300-500 nm and perspective as photocatalytic active materials under visible light irradiation. Paramagnetic behavior with effective magnetic moment 3.92 μB (Bi1.6Cr0.1Ti2O7-δ) and 3.01 μB (Bi1.5Cr0.5Ti2O7) was experimentally observed. All chromium in magnetically diluted pyrochlore Bi1.6Cr0.1Ti2O7-δ exists in the form of Cr3+ monomers, whereas in the more concentrated magnetic Bi1.5Cr0.5Ti2O7 composition Cr3+-O-Cr3+ dimers may also be present, with a fraction equal to 0.39. This investigation constitutes the first approach to the electronic, structural, optical, and magnetic properties of d-elements doped bismuth titanate pyrochlores from experimental and theoretical viewpoints, emphasizing the power of DFT+U to provide insights and to complement the experimental characterization of these new compounds. |
| Databáze: | OpenAIRE |
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