Preparation, crystal structure and thermal expansion of a novel layered borate, Ba{sub 2}Bi{sub 3}B{sub 25}O{sub 44}
- Department of Crystallography, St. Petersburg State University, University Emb 7/9, 199034 St. Petersburg (Russian Federation)
- Kurnakov Institute of General and Inorganic Chemistry of the Russian Academy of Sciences, Leninsky Prospect 31, GSP-1, Moscow 119991 (Russian Federation)
Single crystals of a new compound, Ba{sub 2}Bi{sub 3}B{sub 25}O{sub 44}, were grown by cooling a melt of non-stoichiometric composition. The crystal structure was solved by direct methods and refined to R=0.030 (wR=0.090). The compound is trigonal, R3{sup Macron }m, a=7.851(2), c=46.20(1) A, V=2466.6(6) A{sup 3}, Z=3. The structure is based upon a borate layered anion of the type not previously observed in inorganic compounds. The layer consists of three sublayers; it is {approx}13 A thick and oriented parallel to (001). Two of the sublayers are built from triborate groups, [B{sub 3}O{sub 8}]{sup 7-}, whereas the central sublayer consists of triborate groups, [B{sub 3}O{sub 6}]{sup 3-}. The interlayer space is occupied by the Bi{sup 3+} ions in octahedral coordination. The Ba{sup 2+} cations are located in the cavities within borate layer. The single-phase polycrystalline sample of Ba{sub 2}Bi{sub 3}B{sub 25}O{sub 44} prepared by solid-state reactions from a stoichiometric mixture has been investigated by high-temperature X-ray powder diffraction in air. Anisotropic character of the thermal expansion is not typical for layered structures: {alpha}{sub a}=12, {alpha}{sub c}=6, {alpha}{sub V}=30 Multiplication-Sign 10{sup -6} Degree-Sign S{sup -1} at 25 Degree-Sign S; anisotropy increases on heating: {alpha}{sub a}=12, {alpha}{sub c}=0, {alpha}{sub V}=24 Multiplication-Sign 10{sup -6} Degree-Sign S{sup -1} at 700 Degree-Sign S. - Graphical abstract: Correlation between the pole figure of the thermal expansion coefficients and the structure of Ba{sub 2}Bi{sub 3}B{sub 25}O{sub 44} projected onto ac plane. The pole figures are presented for room temperature and 700 Degree-Sign C. Highlights: Black-Right-Pointing-Pointer A novel borate Ba{sub 2}Bi{sub 3}B{sub 25}O{sub 44} has been synthesized by cooling a non-stoichiometric melt. Black-Right-Pointing-Pointer The crystal structure is based upon a novel borate layered anion ({approx}13 A thick). Black-Right-Pointing-Pointer Anisotropy of thermal expansion increases on heating. Black-Right-Pointing-Pointer Anisotropy dictated by the orientation of triborate groups.
- OSTI ID:
- 22149904
- Journal Information:
- Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Vol. 196; ISSN 0022-4596; ISSN JSSCBI
- Country of Publication:
- United States
- Language:
- English
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