High pressure studies of A2Mo3O12 negative thermal expansion materials (A2=Al2, Fe2, FeAl, AlGa)

High pressure powder X-ray diffraction studies of several A2Mo3O12 materials (A2=Al2, Fe2, FeAl, and AlGa) were conducted up to 6–7GPa. All materials adopted a monoclinic structure under ambient conditions, and displayed similar phase transition behavior upon compression. The initial isotropic compr...

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Bibliographic Details
Published in:Journal of solid state chemistry 2016-05, Vol.237 (C), p.121-128
Main Authors: Young, Lindsay, Gadient, Jennifer, Gao, Xiaodong, Lind, Cora
Format: Article
Language:English
Subjects:
High pressure
in-situ studies
Negative thermal expansion
Phase transitions
Scandium tungstate family
Synchrotron radiation
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Summary:High pressure powder X-ray diffraction studies of several A2Mo3O12 materials (A2=Al2, Fe2, FeAl, and AlGa) were conducted up to 6–7GPa. All materials adopted a monoclinic structure under ambient conditions, and displayed similar phase transition behavior upon compression. The initial isotropic compressibility first became anisotropic, followed by a small but distinct drop in cell volume. These patterns could be described by a distorted variant of the ambient pressure polymorph. At higher pressures, a distinct high pressure phase formed. Indexing results confirmed that all materials adopted the same high pressure phase. All changes were reversible on decompression, although some hysteresis was observed. The similarity of the high pressure cells to previously reported Ga2Mo3O12 suggested that this material undergoes the same sequence of transitions as all materials investigated in this paper. It was found that the transition pressures for all phase changes increased with decreasing radius of the A-site cations. Overlay of variable pressure X-ray diffraction data of Al2Mo3O12 collected in a diamond anvil cell. Both subtle and discontinuous phase transitions are clearly observed. [Display omitted] •The high pressure behavior of A2Mo3O12 (A=Al, Fe, (AlGa), (AlFe)) was studied.•All compounds undergo the same sequence of pressure-induced phase transitions.•The phase transition pressures correlate with the average size of the A-site cation.•All transitions were reversible with hysteresis.•Previously studied Ga2Mo3O12 undergoes the same sequence of transitions.
ISSN:0022-4596
1095-726X
DOI:10.1016/j.jssc.2016.02.004