Enhanced performance of graphite/NiO ink-based flexible thermoelectric generators via compositional gradient and annealing of NiO nanoparticles

Nayak, Ramakrishna; Shetty, Prakash; Selvakumar, M.; Rao, Ashok; Rao, M. Mohan; Subrahmanya, Murari Mudiyaru; Kompa, Akshayakumar; Shanubhogue, Deepika U.

doi:10.1007/s10853-023-08348-z

Cited by 4 publications

(4 citation statements)

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“…Nanoscale grains considerably increase the number of grain boundaries per unit length, which is expected to increase phonon scattering. Moreover, the foreign interface of TiO 2 -graphite is likely to enhance phonon−phonon Umklapp scattering as reported in oxide composite with graphite 18,19 and graphene, 11,21 especially at elevated temperatures. In addition, the presence of oxygen vacancies might also act as phonon scattering centers.…”

Section: ■ Results and Discussionmentioning

confidence: 93%

“…However, this significant increase in electron concentration, accompanied by the reduced Seebeck values, cannot support the presence of Anderson localization in the TiO 2 , unlike the STN-based oxides. 15,18,19 It is rather more likely to be explained by the formation of the Schottky barrier. A Schottky barrier is expected to form in the grain boundary regions of TiO 2 grains blocking the electron flow.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…18−20 Recently, researchers have attained ZT > 1 in Nb-doped SrTiO 3 + graphite, mainly attributed to the order of magnitude increase (14 times) in electron conductivity without much deterioration in the Seebeck coefficient. 19 Incorporation of graphite facilitates high momentum electrons to delocalize the electrons in STN, which otherwise suffers from Anderson localization. In the present investigation, we have incorporated graphite into a simple transition metal oxide, TiO 2 .…”

Section: ■ Introductionmentioning

confidence: 99%

“…Doped SrTiO 3 (STO) is considered one of the promising candidates for n -type oxide thermoelectrics but suffers from poor electrical conductivity. − Interestingly, a significant improvement in electrical conductivity has been found in these oxides when they are incorporated with carbon derivatives such as graphene, − CNT, graphene oxide, MXene, , and graphite. − Recently, researchers have attained ZT > 1 in Nb-doped SrTiO 3 + graphite, mainly attributed to the order of magnitude increase (14 times) in electron conductivity without much deterioration in the Seebeck coefficient . Incorporation of graphite facilitates high momentum electrons to delocalize the electrons in STN, which otherwise suffers from Anderson localization.…”

Section: Introductionmentioning

confidence: 99%

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Synergistic Improvement in Thermoelectric Performance by Forming Environmentally Benign Transition Metal Oxide Composites with Graphite

2023

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In pursuit of developing low-cost, environmentally friendly, thermally stable, production-scalable materials for high-temperature thermoelectric power generation, in this paper, we have posited a strategy of synthesizing composite of simple transition metal oxide with graphite. Among the transition metal oxides, TiO2 is considered as one of the promising n-type thermoelectric materials. Although TiO2 exhibits very high Seebeck coefficient, it suffers from poor electrical conductivity, resulting in a poor thermoelectric figure of merit, ZT. In this work, we have synthesized TiO2 nanocomposites with varying graphite (G) concentration using spark plasma sintering (SPS). We have recorded about 1300% improvement in electrical conductivity of TiO2 due to graphite incorporation, which has been further explained with the help of the percolation model. Electrons are expected to percolate through the three-dimensional conductive channel made of graphite flakes in an insulator-like TiO2 matrix. Moreover, the reduced grain size along with homogeneously distributed graphite also aid in lowering the overall thermal conductivity by suppressing the phonon transport of heat. Synergistic improvement in electrical and thermal transport has allowed us to achieve a ZT of 0.12 at 1000 K that is 140% larger than that of pristine TiO2. Our strategy of nanocomposite formation for high temperature thermoelectric applications employing inexpensive and naturally occurring raw materials such as TiO2 and graphite further opens up the possibility of designing low-cost thermoelectric power generator for recycling high-grade waste heat.

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