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Title: Structural investigation of the “Tripled-Tetragonal-Tungsten-Bronze” Phases Sr 2M 10-xO 27-y (M = Nb, Ta)

Abstract

Sr 2Nb 10O 27 and Sr 2Ta 10-xO 27-y exhibit the tripled tetragonal-tungsten-bronze (TTTB)-related superstructures. In contrast to Sr 2Ta 10-xO 27-y, where an extended solid solution was found, Sr 2Nb 10O 27 only forms a narrow range of solid solution, Sr 1-xNb 10O 27-z (0 ≤ x ≤ 0.04). Serial X-ray and neutron diffraction studies show that both compounds can be modelled in the orthorhombic Pba2 space group. Lattice parameters obtained from powder X-ray refinements are a = 12.4269(2) Å, b = 37.194(7) Å, c = 3.87897(4) Å, for Sr 2Ta 10-xO 27-y, and a = 12.3281(3) Å, b = 37.1561(11) Å, and c = 3.93971(7) Å for Sr 2Nb 10O 27. Neutron Rietveld refinements of both structures revealed the possible reason for the differing solid solution behavior. For Sr 2Nb 10O 27, all Nb sites are fully occupied, whereas in Sr 2Ta 10-xO 27-y, three out of the nine crystallographically unique Ta sites were shown to be partially occupied. Charge adjustment is therefore possible by increasing the Sr concentration, leading to a solid solution series and smaller Ta/Sr ratio as compared to Sr 2Nb 10O 27. In the TTTB-related structures, Nb and Ta ions both occupy octahedral andmore » pentagonal bipyramidal coordination sites. Layers of interconnected corner-shared octahedra were found parallel to the ab plane, with three-, four- and five-fold tunnels found in the structure running parallel to the c-axis. Sr ions partially fill the four- and five-fold tunnels.« less

Authors:
ORCiD logo [1];  [2];  [1];  [2];  [3];  [1]
  1. Univ. of Texas, Dallas, TX (United States)
  2. National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States)
  3. Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
National Science Foundation (NSF); USDOE
OSTI Identifier:
1532476
Grant/Contract Number:  
AC02-06CH11357; DMR-1700030
Resource Type:
Accepted Manuscript
Journal Name:
Polyhedron
Additional Journal Information:
Journal Volume: 170; Journal Issue: C; Journal ID: ISSN 0277-5387
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
Ceramics synthesis; Oxides; Rietveld refinement; Tetragonal tungsten bronze; X-ray and neutron diffraction

Citation Formats

Felder, Justin B., Wong-Ng, Winnie, Qabbani, Rania A., Roth, Robert S., Toby, Brian H., and Chan, Julia Y. Structural investigation of the “Tripled-Tetragonal-Tungsten-Bronze” Phases Sr2M10-xO27-y (M = Nb, Ta). United States: N. p., 2019. Web. doi:10.1016/j.poly.2019.06.003.
Felder, Justin B., Wong-Ng, Winnie, Qabbani, Rania A., Roth, Robert S., Toby, Brian H., & Chan, Julia Y. Structural investigation of the “Tripled-Tetragonal-Tungsten-Bronze” Phases Sr2M10-xO27-y (M = Nb, Ta). United States. doi:10.1016/j.poly.2019.06.003.
Felder, Justin B., Wong-Ng, Winnie, Qabbani, Rania A., Roth, Robert S., Toby, Brian H., and Chan, Julia Y. Sat . "Structural investigation of the “Tripled-Tetragonal-Tungsten-Bronze” Phases Sr2M10-xO27-y (M = Nb, Ta)". United States. doi:10.1016/j.poly.2019.06.003.
@article{osti_1532476,
title = {Structural investigation of the “Tripled-Tetragonal-Tungsten-Bronze” Phases Sr2M10-xO27-y (M = Nb, Ta)},
author = {Felder, Justin B. and Wong-Ng, Winnie and Qabbani, Rania A. and Roth, Robert S. and Toby, Brian H. and Chan, Julia Y.},
abstractNote = {Sr2Nb10O27 and Sr2Ta10-xO27-y exhibit the tripled tetragonal-tungsten-bronze (TTTB)-related superstructures. In contrast to Sr2Ta10-xO27-y, where an extended solid solution was found, Sr2Nb10O27 only forms a narrow range of solid solution, Sr1-xNb10O27-z (0 ≤ x ≤ 0.04). Serial X-ray and neutron diffraction studies show that both compounds can be modelled in the orthorhombic Pba2 space group. Lattice parameters obtained from powder X-ray refinements are a = 12.4269(2) Å, b = 37.194(7) Å, c = 3.87897(4) Å, for Sr2Ta10-xO27-y, and a = 12.3281(3) Å, b = 37.1561(11) Å, and c = 3.93971(7) Å for Sr2Nb10O27. Neutron Rietveld refinements of both structures revealed the possible reason for the differing solid solution behavior. For Sr2Nb10O27, all Nb sites are fully occupied, whereas in Sr2Ta10-xO27-y, three out of the nine crystallographically unique Ta sites were shown to be partially occupied. Charge adjustment is therefore possible by increasing the Sr concentration, leading to a solid solution series and smaller Ta/Sr ratio as compared to Sr2Nb10O27. In the TTTB-related structures, Nb and Ta ions both occupy octahedral and pentagonal bipyramidal coordination sites. Layers of interconnected corner-shared octahedra were found parallel to the ab plane, with three-, four- and five-fold tunnels found in the structure running parallel to the c-axis. Sr ions partially fill the four- and five-fold tunnels.},
doi = {10.1016/j.poly.2019.06.003},
journal = {Polyhedron},
number = C,
volume = 170,
place = {United States},
year = {2019},
month = {6}
}

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This content will become publicly available on June 15, 2020
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