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Multi‐temperature structure of thermoelectric Mg 2 Si and Mg 2 Sn
Author(s) -
Kasai Hidetaka,
Song Lirong,
Andersen Henrik Lyder,
Yin Hao,
Iversen Bo Brummerstedt
Publication year - 2017
Publication title -
acta crystallographica section b
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.604
H-Index - 33
ISSN - 2052-5206
DOI - 10.1107/s2052520617014044
Subject(s) - debye model , annealing (glass) , thermoelectric effect , lattice constant , crystal structure , diffraction , thermal expansion , lattice (music) , debye , crystallography , materials science , analytical chemistry (journal) , synchrotron , chemistry , thermodynamics , metallurgy , physics , organic chemistry , chromatography , acoustics , nuclear physics , optics
A multi‐temperature structural study of Mg 2 Si and Mg 2 Sn was carried out from 100 to 700 K using synchrotron X‐ray powder diffraction. The temperature dependence of the lattice parameters can be expressed as a = 6.3272 (4) + 6.5 (2) × 10 −5 T + 4.0 (3) × 10 −8 T 2 Å and a = 6.7323 (7) + 8.5 (4) × 10 −5 T + 3.8 (5) × 10 −8 T 2 Å for Mg 2 Si and Mg 2 Sn, respectively. The atomic displacement parameters (ADPs) are reported and analysed using a Debye model for the averaged U iso giving Debye temperatures of 425 (2) K for Mg 2 Si and 243 (2) K for Mg 2 Sn. The ADPs are considerably smaller for Mg 2 Si than for Mg 2 Sn reflecting the weaker chemical bonding in the Mg 2 Sn structure. Following the heating, an annealing effect is observed on the lattice parameters and peak widths in both structures, presumably due to changes in the crystal defects, but the lattice thermal expansion is almost unchanged by the annealing. This work provides accurate structural parameters which are of importance for studies of Mg 2 Si, Mg 2 Sn and their solid solutions.