Preparation and Crystal Structures of Bismuth Technetates: A New Metal Oxide System
- UNLV
Two new oxides have been unambiguously identified as Bi{sub 2}Tc{sub 2}O{sub 7-{delta}} with {delta} = 0.14(1) and Bi{sub 3}TcO{sub 8} through X-ray absorption near-edge structure spectroscoy and neutron powder diffraction. The compound Bi{sub 2}Tc{sub 2}O{sub 7-{delta}} has a cubic pyrochlore-type structure with {alpha} = 10.4746(1) {angstrom}, space group Fd{sub 3}m (origin choice 2), and Z = 8. The compound Bi{sub 3}TcO{sub 8} is also cubic, {alpha} = 11.5749(1) {angstrom}, space group P2{sub 1}3, Z = 8, and has a fluorite-related crystal structure. In Bi{sub 2}Tc{sub 2}O{sub 7-{delta}} the Tc(IV) cations are octahedrally coordinated, whereas in Bi{sub 3}TcO{sub 8} the Tc(VII) cations are tetrahedrally coordinated. A third new phase, probably Bi{sub 3}Tc{sub 3}O{sub 11}, could not be obtained pure, but preliminary X-ray powder diffraction data affords a primitive cubic lattice with {alpha} = 9.3433(1) {angstrom}. On the basis of structural similarities between Bi{sub 2}Tc{sub 2}O{sub 7-{delta}} and closely related oxides, Bi{sub 2}Tc{sub 2}O{sub 7-{delta}} is expected to be a metallic oxide with Pauli paramagnetism. Electronic structure calculations of both Bi{sub 2}Tc{sub 2}O{sub 7-{delta}} and Bi{sub 3}TcO{sub 8} further support metallic conductivity in the former and insulating behavior in the latter. The inert pair effect of the Bi cations on the crystal structures of Bi{sub 2}Tc{sub 2}O{sub 7-{delta}} and Bi{sub 3}TcO{sub 8} is also described. In addition, calculations of the valence electron localization function for Bi{sub 2}Tc{sub 2}O{sub 7-{delta}} and Bi{sub 3}TcO{sub 8} provide further visualization of the Bi 6s{sup 2} lone pair electrons in the real space of the crystal structures.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 1006755
- Journal Information:
- Inorg. Chem., Vol. 47, Issue (14) ; 2008; ISSN 0020-1669
- Country of Publication:
- United States
- Language:
- ENGLISH
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