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The Effects of Te 2− and I − Substitutions on the Electronic Structures, Thermoelectric Performance, and Hardness in Melt‐Quenched Highly Dense Cu 2‐ x Se
Author(s) -
Zhao Lanling,
Wang Xiaolin,
Yun Frank F.,
Wang Jiyang,
Cheng Zhenxiang,
Dou Shixue,
Wang Jun,
Snyder G. Jeffrey
Publication year - 2015
Publication title -
advanced electronic materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.25
H-Index - 56
ISSN - 2199-160X
DOI - 10.1002/aelm.201400015
Subject(s) - materials science , thermoelectric effect , fermi level , density functional theory , doping , rietveld refinement , crystallography , crystal structure , band gap , density of states , stoichiometry , condensed matter physics , electronic structure , crystallite , copper , electronic band structure , thermoelectric materials , metallurgy , chemistry , physics , computational chemistry , thermodynamics , composite material , optoelectronics , thermal conductivity , quantum mechanics , electron
A systematic study has been carried out on the electronic band structure and density of states, crystal structures, thermoelectric properties, and hardness of the Cu 2‐ x Se system with and without Te 2− or I − substitutions for Se 2− . Density functional theory calculations indicate that stoichiometric Cu 2 Se is a zero‐gap material, and copper‐deficient Cu 1.875 Se is a p‐type conductor. Te 2– substitution increases the total density of states at the Fermi level, whereas, the I − substitution leads to the reduction of the total and partial density of states for both Se and Cu. Highly dense undoped, Te‐doped, and I‐doped Cu 2‐ x Se bulks have been fabricated by a melt‐quenching method which only takes a few minutes. Rietveld refinements of the X‐ray diffraction patterns reveal that the unit cells are expanded after doping. All the fabricated bulks are p‐type conductors in accordance with band structure calculations, and they all have figure of merit, zT , values over or close to 1.0 at T = 973 K, except for the Cu 2‐ x Te 0.16 Se 0.84 . Furthermore, the hardness is distinctly improved by the doping approach, with a maximum value of ca. 0.66 GPa for the Cu 2‐ x Te 0.16 Se 0.84, which is higher than those of polycrystalline Bi 2 Te 3 and PbTe bulks.