Enhanced Thermoelectric Performance in Oxide Composites of La and Nb Codoped SrTiO₃ by Using Graphite as the Electron Mobility Booster

Abstract

Inherent insulating nature of oxides makes it challenging for use in thermoelectric applications that warrant reasonable electrical conductivity. In the present work, we have used graphite (G) to improve the electron transport in La 0.07 Sr 0.93 Ti 0.93 Nb 0.07 O 3 (LSTN) by making composites. Graphite acts as the electron momentum booster in the LSTN matrix, which otherwise suffers from Anderson localization of electrons, causing an order of magnitude increase in weighted mobility and electrical conductivity. As a result, the thermoelectric power factor increases more than 6 times due to graphite incorporation in LSTN. Furthermore, the lattice thermal conductivity is suppressed due to enhanced Umklapp scattering, as derived from the Debye−Callaway model. Hence, we have recorded ∼423% increment in the figure of merit (ZT) in LSTN + G composites. The maximum ZT obtained is 0.68 at 980 K for the LSTN with 1 wt % graphite composite. Furthermore, we have fabricated a fourlegged n-type thermoelectric power generator demonstrating a milliwatt level power output, which hitherto remained unattainable for oxide thermoelectrics.

Suppression of intrinsic thermal conductivity in Sr1−xGdxTiO3 ceramics via phonon-point defect scattering for enhanced thermoelectric application

“…1,2 The conversion efficiency of the TE module or device is generally determined based on the dimensionless thermoelectric figure of merit ( zT ), and the equation iswhere, S , σ , T and κ are the Seebeck coefficient, electrical conductivity, absolute temperature and total thermal conductivity, respectively. 3 Achieving high zT is complex, where concurrent execution of high σ and S with low κ for material is difficult due to their interrelated property. 4,5 To date, TE materials used in real-time operations are consequently based on the alloy materials such as SiGe, Bi 2 Te 3 and so on but major issues arise due to their scarcity and toxicity.…”

Enhanced Thermoelectric Performance of Rare‐Earth‐Free n‐Type Oxide Perovskite Composite with Graphene Analogous 2D MXene

“…Grain boundary engineering [6,7] and nanocompositing [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] are some of the viable routes to enhance both electron transport and induce more phonon scattering in bulk oxides.Incorporating graphite, [8,9] graphene oxide, [10] and graphene [19,22] into the donor (La, Nb)-doped STO matrix have significantly improved the ZT of STO-based bulk oxides. The most profound aspect of ZT enhancement in doped STO systems reported by various researchers is the single-crystal-like [9,19,23] electron mobility attained in these polycrystalline ceramics when they have formed composites with carbon derivatives. However, the reasons behind such huge surge in electron mobility leading to a manifold increase in electrical conductivity are yet to be fully understood.…”

“…One must decouple the power factor (S 2 σ) and lattice thermal conductivity (κ L ) to attain high ZT values. Grain boundary engineering [6,7] and nanocompositing [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] are some of the viable routes to enhance both electron transport and induce more phonon scattering in bulk oxides.…”

“…Incorporating graphite, [8,9] graphene oxide, [10] and graphene [19,22] into the donor (La, Nb)-doped STO matrix have significantly improved the ZT of STO-based bulk oxides. The most profound aspect of ZT enhancement in doped STO systems reported by various researchers is the single-crystal-like [9,19,23] electron mobility attained in these polycrystalline ceramics when they have formed composites with carbon derivatives. However, the reasons behind such huge surge in electron mobility leading to a manifold increase in electrical conductivity are yet to be fully understood.…”

Designing rare earth-free high entropy oxides with a tungsten bronze structure for thermoelectric applications

“…The most probable explanation for the semiconductor-like electrical conductivity ds/dT 4 0 in spite of possessing such a large electron concentration is Anderson localization [39][40][41] of electrons, as commonly observed in many complex disordered oxides. 1,12,38,[42][43][44][45][46][47][48][49][50] The low electron mobility and high effective mass do reflect the electron localization. The presence of multivalent metal ions, oxygen vacancies, and other atomic disorder causes variation in the local electric field, which eventually leads to electron localization at the bottom of the conduction band.…”