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Substitutional Mechanism of Ni into the Wide-Band-Gap Semiconductor InTaO(4) and Its Implications for Water Splitting Activity in the Wolframite Structure Type.
MedLine Citation:
PMID:  22530995     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
The mechanism of Ni substitution into the oxide semiconductor InTaO(4) has been studied through a combination of structural and spectroscopic techniques, providing insights into its previously reported photoactivity. Magnetic susceptibility and X-ray absorption near-edge spectroscopy (XANES) measurements demonstrate that nickel is divalent within the host lattice. The combined refinement of synchrotron X-ray and neutron powder diffraction data indicates that the product of Ni doping has the stoichiometry of (In(1-x)Ni(2x/3)Ta(x/3))TaO(4) with a solubility limit of x ≈ 0.18, corresponding to 12% Ni on the In site. Single-phase samples were only obtained at synthesis temperatures of 1150 °C or higher due to the sluggish reaction mechanism that is hypothesized to result from small free energy differences between (In(1-x)Ni(2x/3)Ta(x/3))TaO(4) compounds with different x values. Undoped InTaO(4) is shown to have an indirect band gap of 3.96 eV, with direct optical transitions becoming allowed at photon energies in excess of 5.1 eV. Very small band-gap reductions (less than 0.2 eV) result from Ni doping, and the origin of the yellow color of (In(1-x)Ni(2x/3)Ta(x/3))TaO(4) compounds instead results from a weak (3)A(2g) → (3)T(1g) internal d → d transition not associated with the conduction or valence band that is common to oxide compounds with Ni(2+) in an octahedral environment.
Authors:
Andrew C Malingowski; Peter W Stephens; Ashfia Huq; Qingzhen Huang; Syed Khalid; Peter G Khalifah
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-4-24
Journal Detail:
Title:  Inorganic chemistry     Volume:  -     ISSN:  1520-510X     ISO Abbreviation:  -     Publication Date:  2012 Apr 
Date Detail:
Created Date:  2012-4-25     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0366543     Medline TA:  Inorg Chem     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Affiliation:
Department of Chemistry and ‡Department of Physics, State University of New York-Stony Brook , Stony Brook, New York 11794-3400, United States.
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