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Prem Kumar, DS, Tippireddy S, Ramakrishnan A, Chen K-H, Malar P, Mallik RC.  2019.  Thermoelectric and electronic properties of chromium substituted tetrahedrite, 2019. Semiconductor Science and Technology. 34(3):035017.: IOP Publishing AbstractWebsite

Cr substituted tetrahedrites with the chemical formula Cu12−xCrxSb4S13 (x = 0.15, 0.25, 0.35, 0.5, 0.75, 1.0) have been synthesised for thermoelectric study. Cr substitutes at the Cu site to optimize the thermoelectric properties and achieve a higher figure of merit (zT). X-Ray diffraction (XRD) analysis revealed that the tetrahedrite is the major phase with minor impurity phases. Electron probe microanalysis (EPMA) shows the formation of tetrahedrite main phase with near stoichiometry and the presence of Cu3SbS4, CuSbS2 and Sb as secondary phases. X-ray photoelectron spectroscopy (XPS) shows the oxidation state of Cu, Sb and S as +1, +3 and −2, respectively, whereas for Cr, it could not be identified. Temperature-dependent magnetic susceptibility of sample x = 0.75 shows antiferromagnetic correlation originating from the Cr ion. The calculated effective magnetic moment of 2.83 μB per Cr atom indicates the presence of Cr+4 in this sample. The decrease in the electrical resistivity upon doping indicates the compensation of holes due to the substitution of Cr at the Cu site. But the x = 0.35 sample is not following the trend due to larger compensation of holes with an activation energy of 124.6 meV. The temperature-dependent behaviour of electrical resistivity shows the shift in the Fermi level from the valance band towards the band gap. The absolute Seebeck coefficient is positive throughout the temperature range and follows a similar trend as that of electrical resistivity, with the exception of the x = 0.35 sample. The electronic thermal conductivity reduces due to hole compensation caused by Cr substitution. Moreover, the substitution of Cr effectively reduces the lattice thermal conductivity due to point defect scattering of phonons. A maximum zT of 1.0 is achieved for sample x = 0.35 at 700 K.

Pong*, WF, Yeh CL, Chang YD, Tsai M-H, Chang YK, Chen YY, Lee JF, Wei SL, Wen CY, Chen LC, Chen KH, Lin IN, Cheng HF.  2001.  X-ray absorption studies of carbon-related materials. J. of Synchrotron Radiation. 8:145-149.
Pong, WF, Chang YK, Hsieh HH, Tsai MH, Lee KH, Dann TE, Chien FZ, Tseng PK, Tsang KL, Su WK, Chen LC, Wei SL, Chen KH, Bhusari DM, Chen YF.  1998.  Electronic and Atomic Structures of Si-C-N Thin Film by X-ray-absorption Spectroscopy. J. Electron Spectroscopy and Related Pheno.. 92:115.
Pimenov, SM, Frolov VD, Zavedeev EV, Abanshin NP, Du HY, Chen WC, Chen LC, Wu JJ, Chen KH.  2011.  Electron field emission properties of highly dense carbonnanotube arrays. Appl. Phys. A. 105:11.
Philip, J, Hess* P, Feygelson T, Butler JE, Chattopadhyay S, Chen KH, Chen LC.  2003.  Elastic, mechanical, and thermal properties of nanocrystalline diamond films. J. Appl. Phys.. 93:2164-2171.
Pathak, A, Chiou GR, Gade NR, Usman M, Mendiratta S, Luo T-T, Tseng TW, Chen J-W, Chen F-R, Chen K-H, Chen L-C, Lu K-L.  2017.  High-κ Samarium-Based Metal–Organic Framework for Gate Dielectric Applications. ACS Appl. Mater. Interfaces. 9(26):21872–21878.
Pathak, A, Shen J-W, Usman M, Wei L-F, Mendiratta S, Chang Y-S, Sainbileg B, Ngue C-M, Chen R-S, Hayashi M, Luo T-T, Chen F-R, Chen K-H, Tseng T-W, Chen L-C, Lu K-L.  2019.  Integration of a (–Cu–S–)n plane in a metal–organic framework affords high electrical conductivity, 2019. 10(1):1721. AbstractWebsite

Designing highly conducting metal–organic frameworks (MOFs) is currently a subject of great interest for their potential applications in diverse areas encompassing energy storage and generation. Herein, a strategic design in which a metal–sulfur plane is integrated within a MOF to achieve high electrical conductivity, is successfully demonstrated. The MOF {[Cu2(6-Hmna)(6-mn)]·NH4}n (1, 6-Hmna = 6-mercaptonicotinic acid, 6-mn = 6-mercaptonicotinate), consisting of a two dimensional (–Cu–S–)n plane, is synthesized from the reaction of Cu(NO3)2, and 6,6′-dithiodinicotinic acid via the in situ cleavage of an S–S bond under hydrothermal conditions. A single crystal of the MOF is found to have a low activation energy (6 meV), small bandgap (1.34 eV) and a highest electrical conductivity (10.96 S cm−1) among MOFs for single crystal measurements. This approach provides an ideal roadmap for producing highly conductive MOFs with great potential for applications in batteries, thermoelectric, supercapacitors and related areas.

Pao, CW, Babu PD, Tsai HM, Chiou JW, Ray SC, Yang SC, Chien FZ, Pong* WF, Tsai M-H, Hsu CW, Chen LC, Chen KH, Lin H-J, Lee JF, Guo JH.  2006.  Electronic structure of group-III-nitride nanorods studied by x-ray absorption, x-ray emission, and Raman spectroscopy. Appl. Phys. Lett.. 88:223113-(1-3).
Pao, C-W, Wu C-T, Tsai H-M, Liu Y-S, Chang C-L, Pong WF, Chiou J-W, Chen C-W, Hu M-S, Chu M-W, Chen L-C, Chen C-H, Chen K-H, Wang S-B, Chang S-J, Tsai M-H, Lin H-J, Lee J-F, Guo J-H.  2011.  Photoconduction and the electronic structure of silica nanowires embedded with gold nanoparticles. Phys. Rev. B. 84:165412.
and P.D. Kichambare, Chen* LC, Wang CT, Ma KJ, Wu CT, Chen KH.  2001.  Laser irradiation of carbon nanotubes. Materials Chemistry and Physics. 72:218-222.