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Lithium Mobility in the Stannides Li 2 CuSn 2 and Li 2 AgSn 2
Author(s) -
Winter Florian,
Dupke Sven,
Eckert Hellmut,
Rodewald Ute Ch.,
Pöttgen Rainer
Publication year - 2013
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.201300220
Subject(s) - crystallography , tin , lithium (medication) , materials science , niobium , crystal structure , x ray crystallography , diffraction , chemistry , metallurgy , physics , medicine , optics , endocrinology
The stannides Li 2 CuSn 2 and Li 2 AgSn 2 were synthesized by induction‐melting (or in a muffle furnace) of the elements in sealed niobium ampoules. The new phases were characterized by powder X‐ray diffraction. The structures of both stannides were investigated by X‐ray diffraction on single crystals: Li 2 AuSn 2 type, I 4 1 / amd , a = 442.6(1), c = 1940.9(8) pm, wR 2 = 0.0742, 310 F 2 values for Li 2 CuSn 2 and a = 456.33(9) c = 2018.2(6) pm, wR 2 = 0.0626, 339 F 2 values for Li 2 AgSn 2 with 10 variables for each refinement. The transition metal ( T ) atoms have tetrahedral tin coordination. The T Sn 4 tetrahedra are condensed via common corners forming layers that are further condensed by Sn–Sn bonding, leading to three‐dimensional [CuSn 2 ] and [AgSn 2 ] networks which leave distorted hexagonal channels for the lithium atoms. The lithium ions show considerable mobility, with activation energies of 0.29 and 0.47 eV extracted from variable temperature 7 Li solid state NMR spectra. 119 Sn Mössbauer spectra at 78 K show signals at isomer shifts of δ = 2.13(1) mm s –1 for Li 2 CuSn 2 and δ = 2.07(1) mm s –1 for Li 2 AgSn 2 . The signals show electric quadrupolar splitting because of the non spherical environment of the tin nuclei. A minor impurity of β‐Sn could be identified in both spectra.