Bismuth in Ag2BiO3: Tetravalent or Internally Disproportionated?
✍ Scribed by S. Deibele; M. Jansen
- Book ID
- 102608030
- Publisher
- Elsevier Science
- Year
- 1999
- Tongue
- English
- Weight
- 199 KB
- Volume
- 147
- Category
- Article
- ISSN
- 0022-4596
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✦ Synopsis
Black, coarse crystalline samples of Ag 2 BiO 3 have been obtained via solid-state reaction of Ag 2 O and Bi 2 O 3 at an elevated oxygen pressure (250 MPa). The crystal structure determination (Pnna; a ؍ 597.5(1), b ؍ 631.1(1), c ؍ 956.3(2) pm; Z ؍ 4; 749 independent re6ections, R1 ؍ 0.043 %, wR2 ؍ 0.098 %) reveals a three-dimensional framework of distorted, edge-and cornersharing Bi+O octahedra. Silver is in a linear twofold, and in an approximately trigonal planar coordination. The cation partial structure Ag 2 Bi has the same topology as the cubic Laves phase Cu 2 Mg. All bismuth atoms occupy the same crystallographic site and are structurally indistinguishable. Thus, the crystallographic features and composition suggest the presence of tetravalent bismuth. However, this is not compatible with the physical properties (Ag 2 BiO 3 is semiconducting and diamagnetic) observed, and some kind of charge ordering must be assumed. The structural response is weak and not noticeable but in a slight anomaly of one of the thermal displacement parameters.