LiB{sub 3}O{sub 5} crystal structure at 20, 227 and 377 deg. C

• Published in: Journal of solid state chemistry 2005-10, Vol.178 (10)
• Main Authors: Shepelev, Yu.F., Bubnova, R.S., Filatov, S.K., Sennova, N.A., Pilneva, N.A.
• Format: Article
• Language: English
• Subjects: ANISOTROPY; BORATES; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; LITHIUM COMPOUNDS; MONOCRYSTALS; ORTHORHOMBIC LATTICES; TEMPERATURE RANGE 0273-0400 K; TEMPERATURE RANGE 0400-1000 K; THERMAL EXPANSION; X-RAY DIFFRACTION
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1016/j.jssc.2005.06.017

Crystal structure of LiB{sub 3}O{sub 5} (a framework of [B{sub 3}O{sub 5}]{sup -} rings and Li atoms located in interspaces) was refined at high temperatures using single-crystal X-ray diffraction, MoK{alpha}-radiation, anharmonic approximation, orthorhombic; Pna2{sub 1}; Z=4; 20 deg. C (a=8.444, b=7.378, c=5.146 A, 1411 F(hkl), R=0.022); 227 deg. C (a=8.616, b=7.433, c=5.063 A, 1336 F(hkl), R=0.026), 377 deg. C (a=8.746, b=7.480, c=5.013 A, 1193 F(hkl), R=0.035). A high mobility of Li atoms and their highly asymmetric vibrations are revealed. Ellipsoid of Li thermal vibrations is oviform. Li is shifted on heating to 0.26 A mainly along a-axis causing high thermal expansion in this direction; Li temperature factors are multiplied by 4 on heating. Rigid boron-oxygen groups in LiB{sub 3}O{sub 5} remain practically stable on heating similar to {alpha}-Na{sub 2}B{sub 8}O{sub 13} and {alpha}-CsB{sub 5}O{sub 8}. At the same time these groups rotate relative to each other like hinges leading to extremely anisotropic thermal expansion ({alpha}{sub a} =101, {alpha}{sub b} =31, {alpha}{sub c} =-71, {alpha}{sub v} =60x10{sup -6} deg. C{sup -1}, 20-530 deg. C, HTXRPD data). - Graphical abstract: Li anharmonic thermal vibrations in LiB{sub 3}O{sub 5} crystal structures. Display Omitted.