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Title: EXAFS and XRD Studies with Subpicometer Accuracy: The Case of ReO3

Abstract

EXAFS has been measured on ReO3 from 30 to 600 K; XRD has been contemporarily measured above 300 K. In this way, it has been possible to compare the expansion of the lattice parameter (XRD) and of the bond lengths (EXAFS), measured at the same time. EXAFS was interpreted by the cumulant approach, using ReO3 measured at low temperature as reference. According to our results, ReO3 shows a complicated behavior of thermal expansion: (i) ultra low or negative expansion below 100 K, (ii) moderate positive expansion above 150 K up to 500 K, (iii) negative expansion from 500K. up to the decomposition temperature. The EXAFS parallel and perpendicular MSRD (mean square relative displacements) have been calculated for the 1st and 4th shells. An unexpected result is that the perpendicular MSRD of the first coordination shell has a weak temperature dependence.

Authors:
; ;  [1];  [2];  [3];  [4]
  1. Dipartimento di Fisica, Universita di Trento, I-38050, Povo (Trento) (Italy)
  2. Institute of Solid State Physics, University of Latvia, LV-1063 Riga (Latvia)
  3. European Synchrotron Radiation Facility, B.P. 220, F-38043 Grenoble (France)
  4. Istituto di Fotonica e Nanotecnologie del CNR, I-38050, Povo (Trento) (Italy)
Publication Date:
OSTI Identifier:
21054644
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 882; Journal Issue: 1; Conference: XAFS13: 13. international conference on X-ray absorption fine structure, Stanford, CA (United States), 9-14 Jul 2006; Other Information: DOI: 10.1063/1.2644546; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ABSORPTION SPECTROSCOPY; BOND LENGTHS; COMPARATIVE EVALUATIONS; DECOMPOSITION; ELECTRONIC STRUCTURE; FINE STRUCTURE; LATTICE PARAMETERS; RHENIUM OXIDES; TEMPERATURE DEPENDENCE; THERMAL EXPANSION; X-RAY DIFFRACTION; X-RAY SPECTROSCOPY

Citation Formats

Purans, Juris, Dalba, Giuseppe, Fornasini, Paolo, Kuzmin, Alexei, De Panfilis, Simone, and Rocca, Francesco. EXAFS and XRD Studies with Subpicometer Accuracy: The Case of ReO3. United States: N. p., 2007. Web. doi:10.1063/1.2644546.
Purans, Juris, Dalba, Giuseppe, Fornasini, Paolo, Kuzmin, Alexei, De Panfilis, Simone, & Rocca, Francesco. EXAFS and XRD Studies with Subpicometer Accuracy: The Case of ReO3. United States. doi:10.1063/1.2644546.
Purans, Juris, Dalba, Giuseppe, Fornasini, Paolo, Kuzmin, Alexei, De Panfilis, Simone, and Rocca, Francesco. Fri . "EXAFS and XRD Studies with Subpicometer Accuracy: The Case of ReO3". United States. doi:10.1063/1.2644546.
@article{osti_21054644,
title = {EXAFS and XRD Studies with Subpicometer Accuracy: The Case of ReO3},
author = {Purans, Juris and Dalba, Giuseppe and Fornasini, Paolo and Kuzmin, Alexei and De Panfilis, Simone and Rocca, Francesco},
abstractNote = {EXAFS has been measured on ReO3 from 30 to 600 K; XRD has been contemporarily measured above 300 K. In this way, it has been possible to compare the expansion of the lattice parameter (XRD) and of the bond lengths (EXAFS), measured at the same time. EXAFS was interpreted by the cumulant approach, using ReO3 measured at low temperature as reference. According to our results, ReO3 shows a complicated behavior of thermal expansion: (i) ultra low or negative expansion below 100 K, (ii) moderate positive expansion above 150 K up to 500 K, (iii) negative expansion from 500K. up to the decomposition temperature. The EXAFS parallel and perpendicular MSRD (mean square relative displacements) have been calculated for the 1st and 4th shells. An unexpected result is that the perpendicular MSRD of the first coordination shell has a weak temperature dependence.},
doi = {10.1063/1.2644546},
journal = {AIP Conference Proceedings},
number = 1,
volume = 882,
place = {United States},
year = {Fri Feb 02 00:00:00 EST 2007},
month = {Fri Feb 02 00:00:00 EST 2007}
}
  • Bulk tungsten trioxide (WO3) and rhenium trioxide (ReO3) share very similar structures but display different electronic properties. WO3 is a wide bandgap semiconductor while ReO3 is an electronic conductor. With the advanced molecular beam epitaxy techniques, it is possible to make heterostructures comprised of layers of WO3 and ReO3. These heterostructures might display reactivity different than pure WO3 and ReO3. The interactions of two probe molecules (hydrogen and methanol) with the (001) surfaces of WO3, ReO3, and two heterostructures ReO3/WO3 and WO3/ReO3 were investigated at the density functional theory level. Atomic hydrogen prefers to adsorb at the terminal O1C sitesmore » forming a surface hydroxyl on four surfaces. Dissociative adsorption of a hydrogen molecule at the O1C site leads to formation of a water molecule adsorbed at the surface M5C site. This is thermodynamically the most stable state. A thermodynamically less stable dissociative state involves two surface hydroxyl groups O1CH and O2CH. The interaction of molecular hydrogen and methanol with pure ReO3 is stronger than with pure WO3 and the strength of the interaction substantially changes on the WO3/ReO3 and ReO3/WO3 heterostructures. The reaction barriers for decomposition and recombination reactions are sensitive to the nature of heterostructure. The calculated adsorption energy of methanol on WO3(001) of -65.6 kJ/mol is consistent with the previous experimental estimation of -67 kJ/mol. This material is based upon work supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences.« less
  • The control of noxious emissions resulting either from the combustion of fossil fuels or from other industrial activities is one of the most immediate and compelling problems faced by nearly every country in the world. The chemical transformations occurring during the thermal activation of chromium-promoted tin(IV) oxide catalysts have been investigated by vibrational spectroscopy (FT-IR and FT-Raman), powder X-ray diffraction, transmission electron microscopy, and extended X-ray absorption fine structure and near-edge structure. Three methods of catalyst preparation have been employed: impregnation of SnO{sub 2} using aqueous CrO{sub 3} solutions, impregnation of SnO{sub 2} using aqueous chromium(III) nitrate solutions, and coprecipitationmore » from aqueous solutions containing both tin(IV) and chromium(III) ions. The freshly prepared gel catalyst materials comprise small (ca. 1--2 nm) particles of hydrous tin(IV) oxide, on the surface of which are sorbed chromate(VI) anions, {l_brace}Cr(H{sub 2}O){sub 6}{sup 3+}{r_brace} cations, or polymeric {gamma}-CrOOH depending on the preparative route. In all three cases, however, calcination at 573 K results in the formation of the mixed-valence chromium compound Cr{sub 5}O{sub 12}. At higher calcination temperatures Cr{sub 2}O{sub 3} is formed, which becomes more crystalline the higher the temperature. Concurrently, the size of the tin(IV) oxide particles increases, only slowly initially (ca. {times}2 by 673 K and ca. {times}4 by 873 K), but sintering to very large particles occurs at higher temperatures. No incorporation of chromium into the tin(IV) oxide lattice occurs even at high temperature.« less
  • No abstract prepared.