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Unraveling the Impact of Graphene Addition to Thermoelectric SrTiO₃ and La-Doped SrTiO₃ Materials: A Density Functional Theory Study.

ABSTRACT: We present a detailed theoretical investigation of the interaction of graphene with the SrO-terminated (001) surface of pristine and La-doped SrTiO₃. The adsorption of graphene is thermodynamically favorable with interfacial adsorption energies of -0.08 and -0.32 J/m² to pristine SrTiO₃ and La-doped SrTiO₃ surfaces, respectively. We find that graphene introduces C 2p states at the Fermi level, rendering the composite semimetallic, and thus the electrical properties are predicted to be highly sensitive to the amount and quality of the graphene. An investigation of the lattice dynamics predicts that graphene adsorption may lead to a 60-90% reduction in the thermal conductivity due to a reduction in the phonon group velocities, accounting for the reduced thermal conductivity of the composite materials observed experimentally. This effect is enhanced by La doping. We also find evidence that both La dopant ions and adsorbed graphene introduce low-frequency modes that may scatter heat-carrying acoustic phonons, and that, if present, these effects likely arise from stronger phonon-phonon interactions.

SUBMITTER: Tse J

PROVIDER: S-EPMC8414480 | biostudies-literature | 2021 Sep

REPOSITORIES: biostudies-literature

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Unraveling the Impact of Graphene Addition to Thermoelectric SrTiO3 and La-Doped SrTiO3 Materials: A Density Functional Theory Study.

Tse Joshua J Aziz Alex A Flitcroft Joseph M JM Skelton Jonathan M JM Gillie Lisa J LJ Parker Stephen C SC Cooke David J DJ Molinari Marco M

ACS applied materials & interfaces 20210818 34

We present a detailed theoretical investigation of the interaction of graphene with the SrO-terminated (001) surface of pristine and La-doped SrTiO3. The adsorption of graphene is thermodynamically favorable with interfacial adsorption energies of -0.08 and -0.32 J/m2 to pristine SrTiO3 and La-doped SrTiO3 surfaces, respectively. We find that graphene introduces C 2p states at the Fermi level, rendering the composite semimetallic, and thus the electric ...[more]

PMID: 34405998

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Project description:This work considers the enhancement of the thermoelectric figure of merit, ZT, of SrTiO3 (STO) semiconductors by (La, Dy and N) co-doping. We have focused on SrTiO3 because it is a semiconductor with a high Seebeck coefficient compared to that of metals. It is expected that SrTiO3 can provide a high power factor, because the capability of converting heat into electricity is proportional to the Seebeck coefficient squared. This research aims to improve the thermoelectric performance of SrTiO3 by replacing host atoms by La, Dy and N atoms based on a theoretical approach performed with the Vienna Ab Initio Simulation Package (VASP) code. Here, undoped SrTiO3, Sr0.875La0.125TiO3, Sr0.875Dy0.125TiO3, SrTiO2.958N0.042, Sr0.750La0.125Dy0.125TiO3 and Sr0.875La0.125TiO2.958N0.042 are studied to investigate the influence of La, Dy and N doping on the thermoelectric properties of the SrTiO3 semiconductor. The undoped and La-, Dy- and N-doped STO structures are optimized. Next, the density of states (DOS), band structures, Seebeck coefficient, electrical conductivity per relaxation time, thermal conductivity per relaxation time and figure of merit (ZT) of all the doped systems are studied. From first-principles calculations, STO exhibits a high Seebeck coefficient and high figure of merit. However, metal and nonmetal doping, i.e., (La, N) co-doping, can generate a figure of merit higher than that of undoped STO. Interestingly, La, Dy and N doping can significantly shift the Fermi level and change the DOS of SrTiO3 around the Fermi level, leading to very different thermoelectric properties than those of undoped SrTiO3. All doped systems considered here show greater electrical conductivity per relaxation time than undoped STO. In particular, (La, N) co-doped STO exhibits the highest ZT of 0.79 at 300 K, and still a high value of 0.77 at 1000 K, as well as high electrical conductivity per relaxation time. This renders it a viable candidate for high-temperature applications.

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Unraveling the Impact of Graphene Addition to Thermoelectric SrTiO₃ and La-Doped SrTiO₃ Materials: A Density Functional Theory Study.

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Unraveling the Impact of Graphene Addition to Thermoelectric SrTiO<sub>3</sub> and La-Doped SrTiO<sub>3</sub> Materials: A Density Functional Theory Study.

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Unraveling the Impact of Graphene Addition to Thermoelectric SrTiO3 and La-Doped SrTiO3 Materials: A Density Functional Theory Study.

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Unraveling the Impact of Graphene Addition to Thermoelectric SrTiO&lt;sub&gt;3&lt;/sub&gt; and La-Doped SrTiO&lt;sub&gt;3&lt;/sub&gt; Materials: A Density Functional Theory Study.

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Unraveling the Impact of Graphene Addition to Thermoelectric SrTiO₃ and La-Doped SrTiO₃ Materials: A Density Functional Theory Study.

Unraveling the Impact of Graphene Addition to Thermoelectric SrTiO<sub>3</sub> and La-Doped SrTiO<sub>3</sub> Materials: A Density Functional Theory Study.