Crystal structure analysis of tetragonal bronzes {beta}-SrTa{sub 2}O{sub 6} and {beta}'-SrTa{sub 2}O{sub 6} by synchrotron x-ray and neutron powder diffraction.
- Materials Science Division
Strontium ditantalum oxide SrTa{sub 2}O{sub 6} exists in {alpha}-, {beta}-, and {beta}{prime}-polymorphs. Herein the crystal structures of the latter two were studied using synchrotron X-ray and constant-wavelength neutron powder diffraction. While {beta}{prime}-SrTa{sub 2}O{sub 6} [space group P4/mbm, a = 12.47099(1) {angstrom}, c = 3.898210(5) {angstrom}, V = 606.271(2) {angstrom}{sup 3}, Z = 5] belongs to the regular tetragonal tungsten bronze (TTB) family, it contains locally disordered strontium atoms within the pentagonal channel. {beta}-SrTa{sub 2}O{sub 6} [space group Pnam, a = 12.36603(2) {angstrom}, b = 12.43467(2) {angstrom}, c = 7.72403(1) {angstrom}, V = 1187.705(4) {angstrom}{sup 3}, Z = 10] can be described as an orthorhombic modification of the TTB, where the octahedral tilting distortion effectively alleviates the bonding strains around TaO{sub 6} and SrO{sub 13} polyhedra. For comparison, rynersonite type {alpha}-SrTa{sub 2}O{sub 6} [space group Pnma, a = 11.00610(6) {angstrom}, b = 7.63397(3) {angstrom}, c = 5.62634(3) {angstrom}, V = 472.727(5) {angstrom}{sup 3}, and Z = 4] is built from edge-shared dimer units of TaO{sub 6} octahedra. As measured by diffuse-reflection absorption spectroscopy, {alpha}-, {beta}-, and {beta}{prime}-SrTa{sub 2}O{sub 6} have indirect band gap energies of 4.4, 4.0, and 3.8 eV, respectively.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- DE-AC02-06CH11357
- OSTI ID:
- 1049036
- Report Number(s):
- ANL/MSD/JA-72207; JSSCBI; TRN: US1204352
- Journal Information:
- Journal of Solid State Chemistry, Vol. 191, Issue Jul 2012; ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- ENGLISH
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