Structure and lithium ion conductivity of garnet-like Li{sub 5}La{sub 3}Sb{sub 2}O{sub 12} and Li{sub 6}SrLa{sub 2}Sb{sub 2}O{sub 12}
- Sensors and Solid State Ionics, Faculty of Engineering, University of Kiel, Kaiserstr. 2, D24143 Kiel (Germany)
- Mineralogisches Institut der Westf. Wilhelms Universitaet Muenster, Corrensstr. 24, 48149 Muenster (Germany)
- Department of Chemistry, University of Calgary, 2500 University Drive NW, Calgary, AB T2N 1N4 (Canada)
Oxides with the nominal chemical compositions Li{sub 5}La{sub 3}Sb{sub 2}O{sub 12} and Li{sub 6}SrLa{sub 2}Sb{sub 2}O{sub 12} were prepared by solid-state reaction. The structures were refined by the Rietveld method using powder X-ray diffraction data. The synthesis of Li{sub 5}La{sub 3}Sb{sub 2}O{sub 12} resulted in the well known garnet-related structure plus 5 wt.% of La{sub 2}LiSbO{sub 6} in the bulk. In contrast to that, Li{sub 6}SrLa{sub 2}Sb{sub 2}O{sub 12} could be synthesised in single garnet-related type phase. Lithium ion conductivities of Li{sub 5}La{sub 3}Sb{sub 2}O{sub 12} and Li{sub 6}SrLa{sub 2}Sb{sub 2}O{sub 12} were studied by the ac impedance method. The grain-boundary contribution to the total (bulk + grain-boundary) resistance is very small and about 5 and 3% for Li{sub 5}La{sub 3}Sb{sub 2}O{sub 12} and Li{sub 6}SrLa{sub 2}Sb{sub 2}O{sub 12}, respectively, at 24 deg. C and decreases further with increase in temperature. Among the investigated compounds, Li{sub 5}La{sub 3}Sb{sub 2}O{sub 12} exhibits the highest total (bulk + grain-boundary) and bulk ionic conductivity of 7.8 x 10{sup -6} and 8.2 x 10{sup -6} S cm{sup -1}, respectively, at 24 deg. C. The structural data indicate that the coupled substitution Li + Sr {yields} La leads to a closure of the bottle neck like O-O distances of the shared edges of neighbouring Li octahedra and therefore reduces the mobility of Li ions in Li{sub 6}SrLa{sub 2}Sb{sub 2}O{sub 12}. Scanning electron microscope (SEM) images of the Li{sub 6}SrLa{sub 2}Sb{sub 2}O{sub 12} compound revealed well crystallised large homogeneous grains ({approx}4.8 {mu}m) and the grains were in good contact with the neighbouring grain, which leads to a smaller grain-boundary contribution to the total resistance.
- OSTI ID:
- 21143930
- Journal Information:
- Materials Research Bulletin, Vol. 43, Issue 10; Other Information: DOI: 10.1016/j.materresbull.2007.10.035; PII: S0025-5408(07)00486-2; Copyright (c) 2007 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0025-5408
- Country of Publication:
- United States
- Language:
- English
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