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Title: Tuning color through sulfur and fluorine substitutions in the defect tin(II, IV) niobate pyrochlores

Abstract

In this study, sulfur and fluorine substituted Sn 2Nb 2O 7 pyrochlore compounds were synthesized to produce brilliant orange/red colors as an environmentally friendly alternative to other toxic inorganic pigments. Neutron structure refinements indicate that the studied compositions crystallize in the pyrochlore structure with a large number of cation and/or anion vacancies and significant local structural disorder. The cubic unit cell decreases with increasing sulfur and fluorine content. The Sn 2+ cation is off-center by 0.39–0.48 Å from the ideal site, and the oxygen O' is strongly displaced to the 32e position by an extraordinarily large distance that has never been reported for a pyrochlore type phase. The unprecedented displacive disorder and unusual lattice evolution upon sulfur substitution are presumably driven by the strong lone pair stereoactivity associated with Sn 2+. Chemical analysis confirmed the existence of sulfur and fluorine, and 119Sn Mössbauer spectroscopy quantified the presence of both Sn 2+ and Sn 4+ in all compositions. The general formula representative of sulfur-containing pigments is nonstoichiometric Sn$$2+\atop{2-z}$$ (Nb 2-ySn$$4+\atop{y}$$)O 7-z-y/2-xS x with the color varying according to x. The fluorine compound is refined to be Sn$$2+\atop{2}$$(Nb 0·958Ti 0.984Sn$$4+\atop{0.058}$$)O 6·376F 0.206 with exclusively anion vacancies. Optical characterization was performed through diffuse reflectance and color meter measurements. The band gap is determined to be in the range of 2.35 to 2.05 eV as sample color changes from yellow to orange/red. Finally, all powder samples show 60–95% reflectance in the near-infrared (NIR) region, adding new functionality to the application of these compounds as “cool” pigments.

Authors:
 [1];  [1]; ORCiD logo [2];  [3];  [1]
  1. Oregon State Univ., Corvallis, OR (United States). Department of Chemistry
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division
  3. National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States). Center for Neutron Research
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division; USDOE
OSTI Identifier:
1470895
Alternate Identifier(s):
OSTI ID: 1496390
Grant/Contract Number:  
AC05-00OR22725
Resource Type:
Accepted Manuscript
Journal Name:
Solid State Sciences
Additional Journal Information:
Journal Volume: 81; Journal Issue: C; Journal ID: ISSN 1293-2558
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Defect pyrchlores; Anion substitutions; Neutron diffraction; Optical properties; Cool pigments

Citation Formats

Giampaoli, Gabriella, Li, Jun, Hermann, Raphael P., Stalick, Judith K., and Subramanian, M. A. Tuning color through sulfur and fluorine substitutions in the defect tin(II, IV) niobate pyrochlores. United States: N. p., 2018. Web. doi:10.1016/j.solidstatesciences.2018.05.001.
Giampaoli, Gabriella, Li, Jun, Hermann, Raphael P., Stalick, Judith K., & Subramanian, M. A. Tuning color through sulfur and fluorine substitutions in the defect tin(II, IV) niobate pyrochlores. United States. doi:10.1016/j.solidstatesciences.2018.05.001.
Giampaoli, Gabriella, Li, Jun, Hermann, Raphael P., Stalick, Judith K., and Subramanian, M. A. Sat . "Tuning color through sulfur and fluorine substitutions in the defect tin(II, IV) niobate pyrochlores". United States. doi:10.1016/j.solidstatesciences.2018.05.001. https://www.osti.gov/servlets/purl/1470895.
@article{osti_1470895,
title = {Tuning color through sulfur and fluorine substitutions in the defect tin(II, IV) niobate pyrochlores},
author = {Giampaoli, Gabriella and Li, Jun and Hermann, Raphael P. and Stalick, Judith K. and Subramanian, M. A.},
abstractNote = {In this study, sulfur and fluorine substituted Sn2Nb2O7 pyrochlore compounds were synthesized to produce brilliant orange/red colors as an environmentally friendly alternative to other toxic inorganic pigments. Neutron structure refinements indicate that the studied compositions crystallize in the pyrochlore structure with a large number of cation and/or anion vacancies and significant local structural disorder. The cubic unit cell decreases with increasing sulfur and fluorine content. The Sn2+ cation is off-center by 0.39–0.48 Å from the ideal site, and the oxygen O' is strongly displaced to the 32e position by an extraordinarily large distance that has never been reported for a pyrochlore type phase. The unprecedented displacive disorder and unusual lattice evolution upon sulfur substitution are presumably driven by the strong lone pair stereoactivity associated with Sn2+. Chemical analysis confirmed the existence of sulfur and fluorine, and 119Sn Mössbauer spectroscopy quantified the presence of both Sn2+ and Sn4+ in all compositions. The general formula representative of sulfur-containing pigments is nonstoichiometric Sn$2+\atop{2-z}$ (Nb2-ySn$4+\atop{y}$)O7-z-y/2-xSx with the color varying according to x. The fluorine compound is refined to be Sn$2+\atop{2}$(Nb0·958Ti0.984Sn$4+\atop{0.058}$)O6·376F0.206 with exclusively anion vacancies. Optical characterization was performed through diffuse reflectance and color meter measurements. The band gap is determined to be in the range of 2.35 to 2.05 eV as sample color changes from yellow to orange/red. Finally, all powder samples show 60–95% reflectance in the near-infrared (NIR) region, adding new functionality to the application of these compounds as “cool” pigments.},
doi = {10.1016/j.solidstatesciences.2018.05.001},
journal = {Solid State Sciences},
number = C,
volume = 81,
place = {United States},
year = {2018},
month = {5}
}

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