Metallic Ternary Telluride with Sphalerite Superstructure
Abstract
A new ternary compound with composition Cu5Sn2Te7 has been synthesized using the stoichiometric reaction of Cu, Sn, and Te. The compound crystallizes in C2 space group with unit cell parameters of a = 13.549(2) Å, b = 6.0521(11) Å, c = 9.568(2) Å, and β = 98.121(2)°. Cu5Sn2Te7 is a superstructure of sphalerite and exhibits tetrahedral coordination of Cu, Sn, and Te atoms, containing a unique adamantane-like arrangement. The compound is formally mixed valent with a high electrical conductivity of 9.8 × 105 S m-1 at 300 K and exhibits metallic behavior having p-type charge carriers as indicated from the positive Seebeck coefficient. Hall effect measurements further confirm holes as charge carriers with a carrier density of 1.39 × 1021 cm-3 and Hall mobility of 4.5 cm2 V-1 s-1 at 300 K. The electronic band structure calculations indicate the presence of a finite density of states around the Fermi level and agree well with the p-type metallic conductivity. Band structure analysis suggests that the effective mass of the hole state is small and could be responsible for high electronic conductivity and Hall mobility. The high thermal conductivity of 15.1 W m-1 K-1 at 300 K coupled with the low Seebeck coefficient results in a poor thermoelectric figure of merit (ZT) for this compound. Theoretical calculations indicate that if Cu5Sn2Te7 is turned into a valence precise compound by substituting one Cu by a Zn, a semiconducting material, Cu4ZnSn2Te7, with a direct band gap of ~0.5 eV can be obtained.
Recommended Citation
A. Adhikary et al., "Metallic Ternary Telluride with Sphalerite Superstructure," Inorganic Chemistry, vol. 55, no. 5, pp. 2114 - 2122, American Chemical Society (ACS), Mar 2016.
The definitive version is available at https://doi.org/10.1021/acs.inorgchem.5b02516
Department(s)
Physics
Second Department
Chemistry
International Standard Serial Number (ISSN)
0020-1669
Document Type
Article - Journal
Document Version
Citation
File Type
text
Language(s)
English
Rights
© 2016 American Chemical Society (ACS), All rights reserved.
Publication Date
01 Mar 2016