Faculty Publications

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Author: search.filters.author.Bhat, D.K.Subject: search.filters.subject.Alloying

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    High thermoelectric and mechanical performance achieved by a hyperconverged electronic structure and low lattice thermal conductivity in GeTe through CuInTe2 alloying
    (Royal Society of Chemistry, 2023) Kim, H.; Kihoi, S.K.; Shenoy, U.S.; Kahiu, J.N.; Shin, D.H.; Bhat, D.K.; Lee, H.S.
    GeTe-based thermoelectric materials have a very high hole carrier concentration (∼1021 cm−3), and thus, improving the figure of merit, ZT, is substantially challenging. In this work, we foremost dope Bi to lower the majority carrier concentration, followed by alloying CuInTe2 to further adjust the hole concentration to an optimal level (0.5-2.0 × 1020 cm−3). This strategy also improves the structural symmetry and leads to hyperconverged valence sub-bands and resonance levels, increasing the effective mass from 1.42 m0 to 1.95 m0. Consequently, a high power factor of ∼23 μW cm−1 K−2 at room temperature and ∼41 μW cm−1 K−2 at 623 K in the (Ge0.93Bi0.05Te0.98)(CuInTe2)0.01 sample is reported. Moreover, the introduced point defects and nano-deposits reduce the lattice thermal conductivity to amorphous levels. As a result, the (Ge0.93Bi0.05Te0.98)(CuInTe2)0.01 sample has a peak ZT value of ∼2.16 at 623 K and an average ZT value of ∼1.42 at 300-773 K. A record high hardness value (∼277 Hv) is achieved. Simultaneous Bi doping and CuInTe2 alloying appear to be an effective strategy for increasing the ZT values of GeTe-based compounds. © 2023 The Royal Society of Chemistry.
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    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.
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    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