Structural investigation of the negative-thermal-expansion material ZrW2O8

被引:178
作者
Evans, JSO
David, WIF
Sleight, AW
机构
[1] Univ Durham, Dept Chem, Sci Labs, Durham DH1 3LE, England
[2] Rutherford Appleton Lab, ISIS Facil, Didcot OX11 0QX, Oxon, England
[3] Oregon State Univ, Dept Chem, Corvallis, OR 97331 USA
[4] Oregon State Univ, Adv Mat Res Ctr, Corvallis, OR 97331 USA
来源
ACTA CRYSTALLOGRAPHICA SECTION B-STRUCTURAL SCIENCE | 1999年 / 55卷
关键词
D O I
10.1107/S0108768198016966
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
High-resolution powder diffraction data have been recorded on cubic ZTW(2)O(8) [a = 9.18000 (3) Angstrom at 2 K] at 260 temperatures from 2 to 520 K in 2 K steps. These data have confirmed that alpha-ZTW(2)O(8) has a negative coefficient of thermal expansion, alpha = -9.07 x 10(-6) K-1 (2-350 K). A 'parametric' approach to Rietveld refinement is adopted and it is demonstrated that a full anisotropic refinement can be performed at each temperature, despite using a data collection time of only 5 min. Examination of the resulting structural parameters suggests that the origin of the contraction with increasing temperature can be traced straightforwardly to the rigid-body transverse librations of bridging O atoms. alpha-ZrW2O8 undergoes a phase transition from P2(1)3 to Pa (3) over bar at 448 K that is associated with the onset of considerable oxygen mobility. The phase transition can be described in terms of a simple cubic three-dimensional Ising model. Unusual kinetics are associated with this phase transition. Hysteresis in the cell parameter through the phase transition is the opposite of that normally observed.
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页码:333 / 340
页数:8
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