Compressibility, Phase Transitions, and Oxygen Migration in Zirconium Tungstate, ZrW 2 O 8
10.1126/science.275.5296.61
Crossref journal-article
American Association for the Advancement of Science (AAAS)
Science (221)
Abstract

In situ neutron diffraction experiments show that at pressures above 2 kilobars, cubic zirconium tungstate (ZrW 2 O 8 ) undergoes a quenchable phase transition to an orthorhombic phase, the structure of which has been solved from powder diffraction data. This phase transition can be reversed by heating at 393 kelvin and 1 atmosphere and involves the migration of oxygen atoms in the lattice. The high-pressure phase shows negative thermal expansion from 20 to 300 kelvin. The relative thermal expansion and compressibilities of the cubic and orthorhombic forms can be explained in terms of the “cross-bracing” between polyhedra that occurs as a result of the phase transition.

Bibliography

Evans, J. S. O., Hu, Z., Jorgensen, J. D., Argyriou, D. N., Short, S., & Sleight, A. W. (1997). Compressibility, Phase Transitions, and Oxygen Migration in Zirconium Tungstate, ZrW 2 O 8. Science, 275(5296), 61–65.

Authors 6
  1. J S. O. Evans (first)
  2. Z. Hu (additional)
  3. J. D. Jorgensen (additional)
  4. D. N. Argyriou (additional)
  5. S. Short (additional)
  6. A. W. Sleight (additional)
References 25 Referenced 309
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  14. For final refinement higher quality diffraction data were used. The x-ray data was collected from 5° to 100° ( d min = 1.005 Å) with a step size of 0.02° and a counting time of 45 s per step (4522 data points). Neutron data from SEPD Bank 1 with a time of flight of 6 to 29.5 ms (0.803 to 3.95 Å) and 4699 data points were used. Because temperature factors refined from powder data are subject to a number of systematic errors temperature factors were initially set at 0.01 Å 2 for metal atoms and 0.015 Å 2 for O atoms. An absorption correction for neutron data and a surface roughness correction [P. Suortti J. Appl. Crystallogr. 5 325 (1972)] for x-ray data were applied. Absorption parameters were then fixed and equated isotropic temperature factors on individual elements were allowed to refine. On subsequent free refinement of temperature factors individual values remained within acceptable limits. Impurities of 1.1% WO 3 and 0.8% ZrO 2 were included in the refinement as additional phases.
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  16. There is some question as to what constitutes a true W-O bond in the strictest sense and what is a weaker W· · ·O interaction. We choose here to define a W-O bond as one less than 2.3 Å. Using the valence method of Brown and Wu (18) this definition corresponds to interactions contributing greater than 6% of the total valence sum of W being considered as full bonds. A coordination of 4+1 is intended to imply four short (<2.3 Å) and one longer (2.3 to 2.6 Å) interaction.
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  21. Compressibility defined as β = −(1/ V )( dV / dP ). Linear regression of six cell parameters between 0 and 6 kbar yielded linear compressibilities −( l 1 / l 2 )( dl / dP ) of 0.53 × 10 −3 0.47 × 10 −3 and 0.47 × 10 −3 kbar −1 for a b and c respectively.
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  23. Rietveld refinement of high-pressure data was performed with the use of Bank 2 data of SEPD. Time of flight ranged from 4.5 to 26 ms ( d = 0.806 to 4.56 Å) yielding 3071 data points. Data at 0 1.0 3.1 5.2 and 6.2 kbar were refined to χ 2 / wRp values of 1.1/6.5 1.5/4.0 1.4/3.8 1.5/3.9 and 1.4/3.8% respectively. Precise determination of individual bond distances and angles for a structure this complex (33 atoms in an asymmetric unit) is difficult given the lower resolution of the data obtained in the high-pressure cell. Average distances: d avg (Zr-O) = 2.069 − (9 × 10 −4 × P ); d avg (W-O) = 1.809 − (2 × 10 −4 × P ); d avg (Zr-W) = 3.80 − (2 × 10 −4 × P ); d avg (W-W) = 3.904 − (3 × 10 −3 × P ) (pressure in kilobars yields distances in angstroms). Average Zr-O-W angle: 160.3 − (0.14 × P ).
  24. Brown I. D., Wu K. K., Acta Crystallogr. B 32, 1957 (1976). (10.1107/S0567740876006869) / Acta Crystallogr. B by Brown I. D. (1976)
  25. The work at Oregon State was supported by NSF (DMR-9308530) and the Oregon Metals Initiative. The work at Argonne National Laboratory was supported by the U.S. Department of Energy [Office of Basic Energy Sciences Materials Sciences contract U-31-109-ENG-38 (J.D.J. Z.H. S.S.)] and NSF [Office of Science and Technology Centers grant DMR-91-20000 (D.N.A.)].
Dates
Type When
Created 23 years ago (July 27, 2002, 5:37 a.m.)
Deposited 1 year, 7 months ago (Jan. 12, 2024, 10:37 p.m.)
Indexed 22 hours, 53 minutes ago (Aug. 20, 2025, 8:34 a.m.)
Issued 28 years, 7 months ago (Jan. 3, 1997)
Published 28 years, 7 months ago (Jan. 3, 1997)
Published Print 28 years, 7 months ago (Jan. 3, 1997)
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@article{Evans_1997, title={Compressibility, Phase Transitions, and Oxygen Migration in Zirconium Tungstate, ZrW 2 O 8}, volume={275}, ISSN={1095-9203}, url={http://dx.doi.org/10.1126/science.275.5296.61}, DOI={10.1126/science.275.5296.61}, number={5296}, journal={Science}, publisher={American Association for the Advancement of Science (AAAS)}, author={Evans, J S. O. and Hu, Z. and Jorgensen, J. D. and Argyriou, D. N. and Short, S. and Sleight, A. W.}, year={1997}, month=jan, pages={61–65} }