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Enhanced thermoelectric performance of Mg2Si1-xSnx codoped with Bi and Cr

TitleEnhanced thermoelectric performance of Mg2Si1-xSnx codoped with Bi and Cr
Publication TypeJournal Article
Year of Publication2018
Authors,, Johnson, DD, Alam, A
JournalPhysical Review B
Date Published09
Type of ArticleArticle
ISBN Number2469-9950
Accession NumberWOS:000445325800003
Keywordsband-structure, high figure, metals, mg2si, phase segregation, physics, semiconductors, solid-solutions, ternary, total-energy calculations, wave basis-set

= 12.96% Cr), despite its elemental antiferromagnetic state. With alloying of Sn (70.4%), Mg2Si remains an indirect-band-gap semiconductor, but adding small amounts of Bi (3.7%) increases the carrier concentration such that electrons occupy conduction bands, making it a degenerate semiconductor. Mg2Si0.296Sn0.666Bi0.037 is found to give the highest thermoelectric figure of merit (ZT) and power factor (PF) at 700 K, i.e., 1.75 and 7.04 mW m(-1) K-2, respectively. Adding small %Cr decreases ZT and PF to 0.78 and 4.33 mW m(-1) K-2, respectively. Such a degradation in thermoelectric (TE) performance is attributed to two factors: (i) uniform doping acting as an electron acceptor, decreasing conduction, and (ii) the loss of low-lying conduction band degeneracy with doping, decreasing the Seebeck coefficients. A study of configurations of Cr doping suggests that Cr has a tendency to form clusters inside the lattice, which play a crucial role in tuning the magnetic and TE performance of doped Mg2Si compounds.

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Alternate JournalPhys. Rev. B