High-pressure synthesis, crystal and electronic structures of a new scandium tungstate, Sc0.67WO4
Negative thermal expansion (NTE) materials possess a low-density, open structure which 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 Sc₂W₃O₁₂ transforms into a black compound when treated at 4 GPa and 1400 oC. The high pressure phase, Sc ₀.₆₇WO₄, crystallizes in a defect-rich wolframite-type structure, a dense, monoclinic structure (space group P2/c) containing 1-D chains of edge-sharing WO6 octahedra. The chemical bonding of Sc₀.₆₇WO₄ vis-à-vis the ambient pressure Sc₂W₃O₁₂ phase can be understood on the basis of the Sc defect structure. Magnetic susceptibility, resistivity, thermoelectric power and IR spectroscopic measurements reveal that Sc₀.₆₇WO₄ 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:
- Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 989435
- Report Number(s):
- PNNL-SA-70372; KP1704020
- Journal Information:
- Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 7 Vol. 183; ISSN 0022-4596
- Publisher:
- Elsevier
- Country of Publication:
- United States
- Language:
- English
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