The novel borate Lu5Ba6B9O27with a new structure type: synthesis, disordered crystal structure and negative linear thermal expansion
| Autor: | Rimma S. Bubnova, Y.P. Biryukov, Stanislav K. Filatov, A. P. Shablinskii |
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| Rok vydání: | 2019 |
| Předmět: |
Diffraction
Chemistry Metals and Alloys 02 engineering and technology Crystal structure 010402 general chemistry 021001 nanoscience & nanotechnology 01 natural sciences Atomic and Molecular Physics and Optics Thermal expansion 0104 chemical sciences Electronic Optical and Magnetic Materials Crystallography Octahedron Materials Chemistry 0210 nano-technology Thermal analysis Anisotropy Powder diffraction Monoclinic crystal system |
| Zdroj: | Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials. 75:697-703 |
| ISSN: | 2052-5206 |
| DOI: | 10.1107/s2052520619007443 |
| Popis: | Single crystals of Lu5Ba6B9O27were obtained by cooling from a melt and polycrystals of the borate were prepared using a multi-step solid-state synthesis. The crystal structure was determined from single-crystal X-ray diffraction data. The borate crystallizes in a new structure type in the monoclinic crystal system in space groupC2/c, with cell parametersa= 13.0927 (3),b= 9.9970 (2) andc= 20.4884 (4) Å, β = 106.827 (1)°,V= 2566.86 (9) Å3andZ= 4. It is described as a framework composed of rings consisting of vertex-sharing [BO3] triangles and [LuO6] octahedra. The Ba atoms are in the cavities of the framework. The structure is disordered: one of the B atoms is surrounded by six O atoms with partial occupancies of 0.5. The thermal properties of Lu5Ba6B9O27were investigated by thermal analysis and high-temperature X-ray powder diffraction. Its thermal expansion is highly anisotropic. The negative expansion (contraction) is along thebaxis,i.e.parallel to the planes of the largest number of [BO3] triangles. The coefficient of negative linear expansion ranges from −1.42 (at 20°C) to −5.57×10–6 °C–1(at 1000°C). Thermal deformation of theacplane is described in terms of the theory of shear deformation of monoclinic crystals. The Lu5Ba6B9O27sample melts at 1170°C. |
| Databáze: | OpenAIRE |
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