Faculty Publications
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Item Improving the: ZT of SnTe using electronic structure engineering: Unusual behavior of Bi dopant in the presence of Pb as a co-dopant(Royal Society of Chemistry, 2021) Shenoy, U.S.; Bhat, D.K.Electronic structure engineering of SnTe by doping various elements to improve its figure of merit has been the most promising approach recently sought after. Pb doped in SnTe is well known to decrease the thermal conductivity but fails to beneficially tune its electronic properties. Herein, we co-dope Bi in SnTe doped with Pb, to improve the power factor of the material. Bi in the presence of Pb exhibits unusual features not shown in the case of Bi doped SnTe. The synergistic action leads to an increase in the band gap and valence band convergence. Bi also introduces resonance states just below the conduction band edge and causes conduction band convergence. An enhanced power factor due to modification of the electronic structure combined with reduced thermal conductivity translates into an enhanced figure of merit of up to ?1.58 at 800 K as predicted using Boltzmann transport calculations, making it a potential thermoelectric material worthy of further study. This journal is © The Royal Society of Chemistry.Item Synergistic manifestation of band and scattering engineering in the single aliovalent Sb alloyed anharmonic SnTe alloy in concurrence with rule of parsimony(Royal Society of Chemistry, 2021) Basu, R.; Mandava, S.; Shenoy, U.S.; Bhat, D.K.; Khasimsaheb, B.; Debnath, A.K.; Singh, A.; Neeleshwar, S.Several endeavors were adapted to improve the thermoelectric performance of SnTe as a substitute of toxic PbTe and the booming approaches comprise introduction of nanostructuring, resonance states, valence band convergence and interstitial or substitutional defects. In this study, a stratagem was designed to incorporate single aliovalent Sb in SnTe by a one-step approach which successfully modulates the electronic and thermal transport properties by integration of several approaches, viz. energy-filtering effect, valence band convergence and phonon scattering at all length scales synergistically. Here, the alteration of the band structure of SnTe incorporated with Sb leads to substantial improvement of the Seebeck coefficient, essentially beneficial for the performance of thermoelectric alloys, beyond the designated critical temperature at 473 K which shows the onset of strong contribution of the heavy (?) valence band. The experimental finding of band convergence by Sb was for the first time corroborated by theoretical validation by Density Functional Theory (DFT) calculations. In addition, the presence of mass fluctuation, secondary precipitates, interfaces and the long-range interactions due to resonant bonding leading to optical phonon softening, large phase space available for three-phonon scattering and strong anharmonicity enables an ultralow lattice thermal conductivity of ?0.5 W m-1 K-1. Thus, a zT value of ?0.72 at 775 K is recorded for the SnTeSb0.05 composition, which is 154% enhancement compared to our pristine SnTe and is strongly competing with numerous reported zT values using considerably less abundant Ag, Ge, In and highly toxic Pb, Hg, Bi, Cd multiple elements as either a dopant or an additive. Thus, the law of parsimony is maintained with reduction in the cost of the thermoelectric module. © The Royal Society of Chemistry.Item A case of perfect convergence of light and heavy hole valence bands in SnTe: the role of Ge and Zn co-dopants(Royal Society of Chemistry, 2022) Shenoy, U.S.; D, G.K.; Bhat, D.K.A dual step approach of decreasing the thermal conductivity and improving the power factor by using two different dopants has shown great promise in the development of high performance thermoelectrics. In this work, we dope Ge, which is well known to decrease the thermal conductivity of SnTe. Later, to this, we co-dope Zn to simultaneously improve the power factor. Zn, in the presence of Ge, introduces resonance levels, thus distorting the density of states near the Fermi level, improving the room temperature performance. In addition, it is also able to increase the band gap, thus preventing bipolar diffusion at high temperatures. The unique feature exhibited is the perfect convergence of light and heavy hole valence sub-bands achieved for the first time in SnTe promising a high performance throughout the temperature range. The transport property calculations reveal that in addition to p-type, it can also act as an outstanding n-type material by tuning its chemical potential, making it worth studying experimentally. © 2022 RSC.Item Enhanced Electrical, Thermal, and Mechanical Properties of SnTe through Equimolar Multication Alloying for Suitable Device Applications(American Chemical Society, 2024) Kihoi, S.K.; Shenoy, U.S.; Kim, H.; Kahiu, J.N.; Kim, C.M.; Park, K.-I.; Bhat, D.K.; Lee, H.S.With the ever-growing demand for eco-friendly energy sources to mitigate the global rising temperatures, the universal insatiable need for sustainable and efficient energy sources are earnestly being intensively sought after. The ubiquitous heat within, if successfully tapped, is an utterly promising source of energy. To achieve this, a thermoelectric device (TED) is needed. To enhance the conversion efficiency from heat to useful electrical power, we developed a strategy to improve the thermoelectric performance of the materials involved. In this work, equimolar multication alloying (EMMCA) is proposed for the first time and employed to enhance the performance of SnTe-based thermoelectric materials. Beyond the cation’s solubility limit, in situ compositing is observed with an increasing doping ratio, whereby distinct CuInTe2 ternary second phases are dispersed within the SnTe matrix. The electronic properties of the ensuing alloy are significantly enhanced by the resulting carrier concentration modulation and the unique electronic band engineering. A decrease in the thermal transport properties is likewise reported, benefiting from enhanced phonon scattering and diminished electronic contribution. The mechanical properties are also shown to increase with increased alloying. As a result, single-leg TED performance shows substantial output power in comparison with the pristine sample. The outcomes stemming from EMMCA are documented as significantly impactful, contributing to superior overall thermoelectric performance. © 2024 American Chemical Society.Item High figure-of-merit in Zn, Sb co-doped Mg2Si0.3Sn0.7 alloy through simultaneous optimization of electrical and thermal transports(Elsevier Ltd, 2025) Sarkar, P.; Gupta, P.; Shenoy, U.S.; Singh, S.; Kundu, S.; Kumawat, N.; Kedia, D.K.; Bhat, D.K.; Bhattacharya, S.; Singh, A.The derivatives of Mg2Si have recently attracted wide attention as promising thermoelectric materials due to earth abundant and environment friendly low-cost constituents. The main challenge in optimizing the thermoelectric figure of merit ZT, is the low electrical and high thermal conductivities of Mg2Si. The present study demonstrates high ZT of ?1.55 at 673 K in Mg2Si0.3Sn0.7 through simultaneous optimization of electrical and thermal transport through Sb and Zn co-doping. The ultra-low deformation and alloy scattering potentials in Sb and Zn co-doped samples helps in maintaining record high Hall mobility ?70–90 cm2/V.s. The doping induced pudding mold band structure with hyperconvergence in conduction band balances high Seebeck coefficient and high electrical conductivity. The point defects and dislocations created by doping helps in lowering of lattice thermal conductivity as well. The uni-leg power generator fabricated using optimized Mg1.96Zn0.04(Si0.3Sn0.7)0.98Sb0.02 exhibits a record efficiency of ?9.5 % at ?T ? 329 K. © 2025