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

Gabriella Giampaoli; Jun Li; Raphael P. Hermann; Judith K. Stalick; M. A. Subramanian

doi:10.1016/j.solidstatesciences.2018.05.001

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

Gabriella Giampaoli, Jun Li, Raphael P. Hermann, Judith K. Stalick, M. A. Subramanian

Neutron & X-Ray Scattering, & Thermophys

Research output: Contribution to journal › Article › peer-review

11 Scopus citations

Abstract

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−z ²⁺(Nb_2-ySn_y ⁴⁺)O_7-z-y/2-xS_x with the color varying according to x. The fluorine compound is refined to be Sn₂ ²⁺(Nb_0·958Ti_0.984Sn_0.058 ⁴⁺)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. 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.

Original language	English
Pages (from-to)	32-42
Number of pages	11
Journal	Solid State Sciences
Volume	81
DOIs	https://doi.org/10.1016/j.solidstatesciences.2018.05.001
State	Published - Jul 2018

Funding

This work was supported by NSF DMREF Grant Nos. DMR-1508527 (M.A.S.). Work by R. P. H. was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. The research used resources at the Center for Neutron Research at the National Institute of Standards and Technology (NIST), and at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory (ORNL). We thank Dr. Ashfia Huq for collecting some of the neutron diffraction data at ORNL, Mr. Annirudha Pawaskar for assistance in collecting the Mössbauer spectral data, and Dres. T. Watkins and J. Zhang for helpful comments. The identification of any commercial product or trade name does not imply endorsement or recommendation by the National Institute of Standards and Technology. This work was supported by NSF DMREF Grant Nos. DMR-1508527 (M.A.S.). Work by R. P. H. was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division . The research used resources at the Center for Neutron Research at the National Institute of Standards and Technology (NIST), and at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory (ORNL). We thank Dr. Ashfia Huq for collecting some of the neutron diffraction data at ORNL, Mr. Annirudha Pawaskar for assistance in collecting the Mössbauer spectral data, and Dres. T. Watkins and J. Zhang for helpful comments. The identification of any commercial product or trade name does not imply endorsement or recommendation by the National Institute of Standards and Technology. Appendix A

Funders	Funder number
DOE Office of Science
NSF DMREF
National Science Foundation	DMR-1508527
U.S. Department of Energy
National Institute of Standards and Technology	NIST
Office of Science
Basic Energy Sciences
Oak Ridge National Laboratory	ORNL
NIST Center for Neutron Research

Keywords

Anion substitutions
Cool pigments
Defect pyrchlores
Neutron diffraction
Optical properties

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10.1016/j.solidstatesciences.2018.05.001

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@article{fc3f712b924447358d72b67e53eb32bb,

title = "Tuning color through sulfur and fluorine substitutions in the defect tin(II, IV) niobate pyrochlores",

abstract = "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 {\AA} 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 M{\"o}ssbauer spectroscopy quantified the presence of both Sn2+ and Sn4+ in all compositions. The general formula representative of sulfur-containing pigments is nonstoichiometric Sn2−z 2+(Nb2-ySny 4+)O7-z-y/2-xSx with the color varying according to x. The fluorine compound is refined to be Sn2 2+(Nb0·958Ti0.984Sn0.058 4+)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. 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.",

keywords = "Anion substitutions, Cool pigments, Defect pyrchlores, Neutron diffraction, Optical properties",

author = "Gabriella Giampaoli and Jun Li and Hermann, {Raphael P.} and Stalick, {Judith K.} and Subramanian, {M. A.}",

note = "Publisher Copyright: {\textcopyright} 2018 Elsevier Masson SAS",

year = "2018",

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doi = "10.1016/j.solidstatesciences.2018.05.001",

language = "English",

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T1 - Tuning color through sulfur and fluorine substitutions in the defect tin(II, IV) niobate pyrochlores

AU - Giampaoli, Gabriella

AU - Li, Jun

AU - Hermann, Raphael P.

AU - Stalick, Judith K.

AU - Subramanian, M. A.

PY - 2018/7

Y1 - 2018/7

N2 - 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 Sn2−z 2+(Nb2-ySny 4+)O7-z-y/2-xSx with the color varying according to x. The fluorine compound is refined to be Sn2 2+(Nb0·958Ti0.984Sn0.058 4+)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. 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.

AB - 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 Sn2−z 2+(Nb2-ySny 4+)O7-z-y/2-xSx with the color varying according to x. The fluorine compound is refined to be Sn2 2+(Nb0·958Ti0.984Sn0.058 4+)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. 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.

KW - Anion substitutions

KW - Cool pigments

KW - Defect pyrchlores

KW - Neutron diffraction

KW - Optical properties

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DO - 10.1016/j.solidstatesciences.2018.05.001

M3 - Article

AN - SCOPUS:85046844451

SN - 1293-2558

VL - 81

SP - 32

EP - 42

JO - Solid State Sciences

JF - Solid State Sciences

ER -

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

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