Ab Initio and Experimental Insights on Structural, Electronic, Optical, and Magnetic Properties of Cr-Doped Bi 2 Ti 2 O 7
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 correction (DFT+U) to account for on-site Coulomb interactions of the Cr 3...
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Veröffentlicht in: | Inorganic chemistry 2019-08, Vol.58 (15), p.9904-9915 |
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Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | 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
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 Bi
Cr
Ti
O
(Bi site doping) in a fine powder state was shown via coprecipitation method, while the single-phase Bi
Ti
Cr
O
(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, Bi
Cr
Ti
O
compound is an A-site deficient pyrochlore (Bi
Cr
)(Ti
Cr
)O
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 (Bi
Cr
Ti
O
) and 3.01 μB (Bi
Cr
Ti
O
) was experimentally observed. All chromium in magnetically diluted pyrochlore Bi
Cr
Ti
O
exists in the form of Cr
monomers, whereas in the more concentrated magnetic Bi
Cr
Ti
O
composition Cr
-O-Cr
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. |
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ISSN: | 0020-1669 1520-510X |
DOI: | 10.1021/acs.inorgchem.9b01057 |