@article{ISI:000431151200004,
 abstract = {A detailed theoretical and experimental study is carried out to
understand the effect of transition metal atom (TM) substitution at the
Cu tetrahedral site in synthetic tetrahedrite material Cu12-xTMxSb4S13
(TM = Mn, Fe, Co, Ni, and Zn). The samples are prepared by solid state
synthesis method with the desired compositions. The X-ray diffraction
(XRD) pattern of all the samples reveal tetrahedrite as the main phase
with traces of secondary phases, confirmed by Electron Probe Micro
Analysis (EPMA). X-ray Photoelectron Spectroscopy (XPS) reveals that TM
is in +2 oxidation state for all samples except for Fe which shows a + 3
oxidation state. Ultraviolet Photoelectron Spectroscopy (UPS)
measurements show the highest work function for Cu11.5Co0.5Sb4S13,
indicating high band degeneracy. Density Functional Theory (DFT)
calculations reveal that TM substitution introduces spin polarized
states within the band structure, thus, changing the band degeneracy and
density of states (DOS) at the Fermi level (E-F). It is confirmed from
DFT calculations that band degeneracy is highest for Cu11.5Co0.5Sb14S13
among the TM substituted samples, with high DOS at E-F, which is
experimentally confirmed by magnetic susceptibility analysis. The
electrical resistivity (rho) and Seebeck coefficients (S) of the
substituted samples are higher than the pristine compound due to
compensation of holes caused by substitution of TM+2 or TM+3 on the Cu
tetrahedral site. Because of the high band degeneracy and DOS at EF, a
high power factor is achieved for the composition Cu11.5Co0.5Sb14S13,
enabling it to attain the maximum figure of merit (zT) among the
substituted tetrahedrite compositions. The paper presents a
comprehensive study to understand the role of magnetic impurities (TM)
in influencing the band structure and, hence, the transport properties
in substituted tetrahedrite.},
 author = {Tippireddy, Sahil and Chetty, Raju and Naik, Mit H. and Jain, Manish and
Chattopadhyay, Kamanio and Mallik, Ramesh Chandra},
 doi = {10.1021/acs.jpcc.7b12214},
 issn = {1932-7447},
 journal = {JOURNAL OF PHYSICAL CHEMISTRY C},
 month = {APR 26},
 number = {16},
 orcid-numbers = {Tippireddy, Sahil/0000-0002-5383-6966
Mallik, Ramesh Chandra/0000-0002-8383-7812
Jain, Manish/0000-0001-9329-6434
Chetty, Raju/0000-0003-1072-8241},
 pages = {8735-8749},
 researcherid-numbers = {Tippireddy, Sahil/AAW-2878-2020
Mallik, Ramesh Chandra/I-5814-2019
Jain, Manish/A-8303-2010
Chetty, Raju/G-4136-2016},
 times-cited = {21},
 title = {Electronic and Thermoelectric Properties of Transition Metal Substituted
Tetrahedrites},
 unique-id = {ISI:000431151200004},
 volume = {122},
 year = {2018}
}