High-pressure synthesis, crystal and electronic structures of a new scandium tungstate, Sc{sub 0.67}WO{sub 4}.
Negative thermal expansion (NTE) materials possess a low-density, open structure that can respond to high pressure conditions, leading to new compounds and/or different physical properties. Here we report that one such NTE material - white, insulating, orthorhombic Sc{sub 2}W{sub 3}O{sub 12} - transforms into a black compound when treated at 4 GPa and 1400 C. The high pressure phase, Sc{sub 0.67}WO{sub 4}, crystallizes in a defect-rich wolframite-type structure, a dense, monoclinic structure (space group P2/c) containing 1-D chains of edge-sharing WO{sub 6} octahedra. The chemical bonding of Sc{sub 0.67}WO{sub 4} vis-a-vis the ambient pressure Sc{sub 2}W{sub 3}O{sub 12} phase can be understood on the basis of the Sc defect structure. Magnetic susceptibility, resistivity, thermoelectric power and IR spectroscopic measurements suggest that the Sc{sub 0.67}WO{sub 4} sample is a paramagnet whose conductivity is that of a metal in the presence of weak localization and electron-electron interactions. Oxygen vacancies are suggested as a potential mechanism for generating the carriers in this defective wolframite material.
- Research Organization:
- Argonne National Laboratory (ANL)
- Sponsoring Organization:
- SC
- DOE Contract Number:
- AC02-06CH11357
- OSTI ID:
- 979885
- Report Number(s):
- ANL/MSD/JA-65991
- Journal Information:
- J. Solid State Chem., Journal Name: J. Solid State Chem. Journal Issue: 7 ; 2010 Vol. 183; ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- ENGLISH
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