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Title: The structure and ordering of zirconium and hafnium containing garnets studied by electron channelling, neutron diffraction and Moessbauer spectroscopy

Abstract

Garnets, A {sub 3} B {sub 2}C{sub 3}O{sub 12}, are an important group of minerals and have potential uses in the safe immobilisation of high-level nuclear waste. They have been found naturally to incorporate Zr, Ti and Fe, three elements of interest in the safe storage of nuclear waste. Kimzeyite, Ca{sub 3}(Zr,Ti){sub 2}(Si,Al,Fe){sub 3}O{sub 12}, is a naturally occurring garnet that contains Zr in a high percentage{approx}30 wt%. For such a material to be of potential immobilisation for nuclear waste the structure needs to be completely understood. Electron channelling studies have shown that the Zr/Ti cations are located on the Y-site, with the Al/Fe cations located on the Z-site. This work has investigated synthetic analogues of kimzeyite, Ca{sub 3}(Zr,Hf){sub 2}(Al,Fe,Si){sub 3}O{sub 12}, by neutron powder diffraction, using the C2 spectrometer at the Chalk River nuclear facility, coupled with {sup 57}Fe Moessbauer spectroscopy. Such work has allowed the structure of the synthetic material to be determined along with the distribution of cations across the X (CN=8), Y (CN=6), and Z (CN=4) sites. Results have shown that it is possible to synthesise Ca{sub 3}(Zr,Hf){sub 2}(Al,Fe,Si){sub 3}O{sub 12} with a range of Al/Fe ratios containing Zr and Hf. The Moessbauer data has indicatedmore » the Fe is located on the Z site. The structural analyses show that the unit cell changes linearly as a function of composition, and analysis of the disorder indicates that the Zr, Hf reside on the Y site and the Al, Fe, and Si reside on the Z site. - Graphical abstract: Dynamical diffraction pattern for kimzeyite along the 3 1 1 direction, used in the electron channelling analysis, and a bright field image of the sample investigated, the magnification is 25 000.« less

Authors:
 [1];  [2];  [1];  [3];  [4];  [4];  [5];  [6];  [7]
  1. Department of Earth Sciences, Downing Street, Cambridge, CB2 3EQ (United Kingdom)
  2. (United Kingdom), E-mail: k.r.whittle@shef.ac.uk
  3. (Australia)
  4. Department of Chemistry, The Open University, Walton Hall, Milton Keynes, MK7 6AA (United Kingdom)
  5. Materials Division, Australian Nuclear Science and Technology Organisation, Private Mail Bag 1, Menai, NSW 2234 (Australia)
  6. Institute of Geology of Ore Deposits, Russian Academy of Sciences (RAS), Staromonetnii Pereulok 35, Moscow 109017 (Russian Federation)
  7. Materials Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States)
Publication Date:
OSTI Identifier:
21015711
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 180; Journal Issue: 2; Other Information: DOI: 10.1016/j.jssc.2006.12.006; PII: S0022-4596(06)00644-X; Copyright (c) 2006 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ALUMINIUM COMPOUNDS; CYANIDES; GARNETS; HAFNIUM COMPOUNDS; HIGH-LEVEL RADIOACTIVE WASTES; IRON COMPOUNDS; MOESSBAUER EFFECT; NEUTRON DIFFRACTION; OXIDES; SILICON COMPOUNDS; SYNTHETIC MATERIALS; TITANIUM COMPOUNDS; ZIRCONIUM COMPOUNDS

Citation Formats

Whittle, Karl R., Department of Engineering Materials, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield, S1 3JD, Lumpkin, Gregory R., Materials Division, Australian Nuclear Science and Technology Organisation, Private Mail Bag 1, Menai, NSW 2234, Berry, Frank J., Oates, Gordon, Smith, Katherine L., Yudintsev, Sergey, and Zaluzec, Nestor J.. The structure and ordering of zirconium and hafnium containing garnets studied by electron channelling, neutron diffraction and Moessbauer spectroscopy. United States: N. p., 2007. Web. doi:10.1016/j.jssc.2006.12.006.
Whittle, Karl R., Department of Engineering Materials, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield, S1 3JD, Lumpkin, Gregory R., Materials Division, Australian Nuclear Science and Technology Organisation, Private Mail Bag 1, Menai, NSW 2234, Berry, Frank J., Oates, Gordon, Smith, Katherine L., Yudintsev, Sergey, & Zaluzec, Nestor J.. The structure and ordering of zirconium and hafnium containing garnets studied by electron channelling, neutron diffraction and Moessbauer spectroscopy. United States. doi:10.1016/j.jssc.2006.12.006.
Whittle, Karl R., Department of Engineering Materials, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield, S1 3JD, Lumpkin, Gregory R., Materials Division, Australian Nuclear Science and Technology Organisation, Private Mail Bag 1, Menai, NSW 2234, Berry, Frank J., Oates, Gordon, Smith, Katherine L., Yudintsev, Sergey, and Zaluzec, Nestor J.. Thu . "The structure and ordering of zirconium and hafnium containing garnets studied by electron channelling, neutron diffraction and Moessbauer spectroscopy". United States. doi:10.1016/j.jssc.2006.12.006.
@article{osti_21015711,
title = {The structure and ordering of zirconium and hafnium containing garnets studied by electron channelling, neutron diffraction and Moessbauer spectroscopy},
author = {Whittle, Karl R. and Department of Engineering Materials, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield, S1 3JD and Lumpkin, Gregory R. and Materials Division, Australian Nuclear Science and Technology Organisation, Private Mail Bag 1, Menai, NSW 2234 and Berry, Frank J. and Oates, Gordon and Smith, Katherine L. and Yudintsev, Sergey and Zaluzec, Nestor J.},
abstractNote = {Garnets, A {sub 3} B {sub 2}C{sub 3}O{sub 12}, are an important group of minerals and have potential uses in the safe immobilisation of high-level nuclear waste. They have been found naturally to incorporate Zr, Ti and Fe, three elements of interest in the safe storage of nuclear waste. Kimzeyite, Ca{sub 3}(Zr,Ti){sub 2}(Si,Al,Fe){sub 3}O{sub 12}, is a naturally occurring garnet that contains Zr in a high percentage{approx}30 wt%. For such a material to be of potential immobilisation for nuclear waste the structure needs to be completely understood. Electron channelling studies have shown that the Zr/Ti cations are located on the Y-site, with the Al/Fe cations located on the Z-site. This work has investigated synthetic analogues of kimzeyite, Ca{sub 3}(Zr,Hf){sub 2}(Al,Fe,Si){sub 3}O{sub 12}, by neutron powder diffraction, using the C2 spectrometer at the Chalk River nuclear facility, coupled with {sup 57}Fe Moessbauer spectroscopy. Such work has allowed the structure of the synthetic material to be determined along with the distribution of cations across the X (CN=8), Y (CN=6), and Z (CN=4) sites. Results have shown that it is possible to synthesise Ca{sub 3}(Zr,Hf){sub 2}(Al,Fe,Si){sub 3}O{sub 12} with a range of Al/Fe ratios containing Zr and Hf. The Moessbauer data has indicated the Fe is located on the Z site. The structural analyses show that the unit cell changes linearly as a function of composition, and analysis of the disorder indicates that the Zr, Hf reside on the Y site and the Al, Fe, and Si reside on the Z site. - Graphical abstract: Dynamical diffraction pattern for kimzeyite along the 3 1 1 direction, used in the electron channelling analysis, and a bright field image of the sample investigated, the magnification is 25 000.},
doi = {10.1016/j.jssc.2006.12.006},
journal = {Journal of Solid State Chemistry},
number = 2,
volume = 180,
place = {United States},
year = {Thu Feb 15 00:00:00 EST 2007},
month = {Thu Feb 15 00:00:00 EST 2007}
}
  • Some new compounds with garnet-related structures have been examined by {sub 57}Fe Moessbauer spectroscopy. The results show that in compounds of the type YCa{sub 2}SbFe{sub 4-x}Ga{sub x}O{sub 12} (x = 2,3) the gallium is distributed over both the octahedral and tetrahedral sites. In these compounds, together with materials of composition Y{sub 3-2x}Ca{sub 2x}Sb{sub x}Fe{sub 5-x}O{sub 12} (x = 1.25, 1.5) and Y{sub 3-x}Ca{sub x}Sn{sub x}Fe{sub 5-x}O{sub 12}(x = 1,2), the results show evidence of more than one tetrahedral environment for the Fe{sup 3+} ions. The quadrupole splitting data for the Fe{sup 3+} ions in tetrahedral sites in some of thesemore » compounds are significantly larger than those previously reported for Fe{sup 3+} in tetrahedral sites in other garnets.« less
  • A clean surface of LaB/sub 6/(210) exhibits the low work function of 2.2 +- 0.1 eV at room temperature. This is lower than those of the (100), (110), and (111) surfaces. Similarly to the (100) surface, La atoms exist in a (1 x 1) ordered structure at the outermost layer of the (210) clean surface. The value of the low work function of LaB/sub 6/ has been discussed on the basis of those data together with the Lang-Kohn theory. The changes of the (210) surface with oxygen chemisorption are more analogous to those of the (110) surface than the (100)more » and (111) surface. Work function changes from 2.2 to 3.1 eV with oxygen exposure and saturates above approx.15 L; the periodicity of the surface-atomic lattice disappears almost completely.« less
  • Aspects of the nuclear and magnetic structure of the three-dimensionally ordered state of the layered system Fe(III)ClMoO/sub 4/ are elucidated primarily on the basis of single crystal and powder Moessbauer spectroscopy and neutron powder diffraction refinements at various temperatures. The antiferromagnetically coupled spins and easy axis of magnetization for Fe(III)ClMoO/sub 4/ are indicated to lie in the tetragonal layers (ab planes) perpendicular to the c axis, which is parallel to the Fe-Cl bond vector of a local C/sub 4v/ FeO/sub 4/Cl chromophore. Additionally, the neutron diffraction data indicate a very significant c-axis contraction with decreasing temperature (2.7% between 295 andmore » 5 K), with the rate of contraction being highest in the vicinity of the Neel temperature, T/sub N/ (approx. 70 K). The structural changes that occur in the temperature range 300 to 5 K are discussed. Powder and single crystal magnetic susceptibility results to approx. 1.6 K as well as high field Moessbauer spectra to approx. 9 T are also presented. The latter indicate a spin flop transition with H/sub sf/ approx. 1 T. Alternate views of the low-dimensional magnetism of FeClMoO/sub 4/, evident as a broad maximum in its molar susceptibility at approx. 105 K, are discussed.« less
  • Fe-Si alloys with Si-contents up to 14 at.%Si (7.6 wt.%Si ) were produced by conventional casting and hot/cold rolled with different conditions of temperatures, pass reductions and cooling rates. The obtained thickness of the final sheet was between 0.5 and 0.7 mm for Si-steel up to 10 at.%Si (5.5 wt.%). Moessbauer spectroscopy was used to characterize the order evolution with the Si-content and the thermomechanical processing of the material. A new fitting program was developed for this purpose due to the known complexity of the Fe-alloys spectra. Results show that there is never complete disorder, i.e. binomial distribution of themore » atoms, whatever the Si-concentration is. Moreover, a clear tendency towards D03 ordering is observed. The obtained long-range order parameters prove a patent increase of the D03 order above 7 at.%Si (3.6 wt.%) which can be associated to the observed brittleness beyond this Si-amount. Concerning the relationship between order and thermomechanical processing, no big effect was found for low Si-contents (up to 6 at.%Si), while for higher amounts two results are clearly observed: (i) the slower the cooling after the hot rolling is, the higher the order is and (ii) cold deformation removes order in a great way. This agrees with the need of fast cooling after hot rolling in order to increase the cold workability of the Si-steel.« less
  • By means of powder neutron diffraction investigations, chemical structure and magnetic Ce ordering of Ce{sub 0.75}La{sub 0.25}{sup 11}B{sub 6} have been investigated at temperatures down to 105 mK. In the antiferromagnetic low-temperature phase III Ce{sub 0.75}La{sub 0.25}{sup 11}B{sub 6} resembles pure CeB{sub 6}, but has a lower Neel temperature T{sub N} between 0.89 and 1.25 K. Similar to the recently determined magnetic ordering in pure CeB{sub 6} (model C), one obtains the compared to CeB{sub 6} smaller ordered magnetic Ce moments {mu}{sub Ce(1)}=0.53(1) {mu}{sub B} at z=0 and {mu}{sub Ce(2)}=0.12(1) {mu}{sub B} at z=1/2 with respect to the magnetic unitmore » cell at 105 mK. Presumably this magnetic ordering, which is characterized by both propagation vectors k=[1/4,1/4,0] and k{sup '}=[1/4,1/4,1/2], is caused by competition between magnetic dipole and multipolar ordering. At 0.89 K the magnetic moments are reduced to {mu}{sub Ce(1)}=0.31(1){mu}{sub B} and {mu}{sub Ce(2)}=0.08(1){mu}{sub B}. At 1.25 K in phase IV with presumably multipolar Ce ordering no significant magnetic Bragg peaks associated with magnetic dipole Ce moments were observed, supporting the octupole model of Kubo and Kuramoto for this phase.« less