Prospects for engineering thermoelectric properties in La1/3NbO3 ceramics revealed via atomic-level characterization and modelling

Demie Kepaptsoglou, Jakub Baran, F Azough, Dursun Ekren, Deepanshu Srivastava, Marco Molinari, Stephen C. Parker, Quentin Mathieu Ramasse, R Freer

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Abstract

A combination of experimental and computational techniques has been employed to explore the crystal structure and thermoelectric properties of A-site deficient perovskite La1/3NbO3 ceramics. Crystallographic data from X-ray and electron diffraction confirmed that the room temperature structure is orthorhombic with Cmmm as a space group. Atomically resolved imaging and analysis showed that there are two distinct A-sites: one is occupied with La and vacancies and the second site is fully un-occupied; the diffuse super-structure reflections observed through diffraction techniques are shown to originate from La vacancy ordering. La1/3NbO3 ceramics sintered in air showed promising high temperature thermoelectric properties with a high Seebeck coefficient of S1 = -650 to -700 µV/K and a low and temperature-stable thermal conductivity of k = 2 to 2.2 W/mK in the temperature range of 300 to1000 K. First-principles electronic structure calculations are used to link the temperature dependence of the Seebeck coefficient measured experimentally to the evolution of the density of states with temperature and indicate possible avenues for its further optimization through electron doping and control of the A-site occupancies. Moreover, lattice thermal conductivity calculations give an insight into the dependence of the thermal conductivity on specific crystallographic directions of the material, which could be exploited via nano-structuring to create high-efficiency compound thermoelectrics.
LanguageEnglish
Pages45-55
JournalInorganic Chemistry
Volume57
Issue number1
Early online date19 Dec 2017
DOIs
StatusPublished - 2018

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thermal conductivity
engineering
ceramics
Seebeck effect
Thermal conductivity
Seebeck coefficient
diffraction
Temperature
Vacancies
temperature
electron diffraction
electronic structure
temperature dependence
crystal structure
optimization
air
room temperature
Electron diffraction
Electronic structure
electrons

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Prospects for engineering thermoelectric properties in La1/3NbO3 ceramics revealed via atomic-level characterization and modelling. / Kepaptsoglou, Demie; Baran, Jakub; Azough, F; Ekren, Dursun; Srivastava, Deepanshu; Molinari, Marco; Parker, Stephen C.; Ramasse, Quentin Mathieu; Freer, R.

In: Inorganic Chemistry, Vol. 57, No. 1, 2018, p. 45-55.

Research output: Contribution to journalArticle

Kepaptsoglou, D, Baran, J, Azough, F, Ekren, D, Srivastava, D, Molinari, M, Parker, SC, Ramasse, QM & Freer, R 2018, 'Prospects for engineering thermoelectric properties in La1/3NbO3 ceramics revealed via atomic-level characterization and modelling', Inorganic Chemistry, vol. 57, no. 1, pp. 45-55. https://doi.org/10.1021/acs.inorgchem.7b01584
Kepaptsoglou, Demie ; Baran, Jakub ; Azough, F ; Ekren, Dursun ; Srivastava, Deepanshu ; Molinari, Marco ; Parker, Stephen C. ; Ramasse, Quentin Mathieu ; Freer, R. / Prospects for engineering thermoelectric properties in La1/3NbO3 ceramics revealed via atomic-level characterization and modelling. In: Inorganic Chemistry. 2018 ; Vol. 57, No. 1. pp. 45-55.
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AU - Molinari, Marco

AU - Parker, Stephen C.

AU - Ramasse, Quentin Mathieu

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AB - A combination of experimental and computational techniques has been employed to explore the crystal structure and thermoelectric properties of A-site deficient perovskite La1/3NbO3 ceramics. Crystallographic data from X-ray and electron diffraction confirmed that the room temperature structure is orthorhombic with Cmmm as a space group. Atomically resolved imaging and analysis showed that there are two distinct A-sites: one is occupied with La and vacancies and the second site is fully un-occupied; the diffuse super-structure reflections observed through diffraction techniques are shown to originate from La vacancy ordering. La1/3NbO3 ceramics sintered in air showed promising high temperature thermoelectric properties with a high Seebeck coefficient of S1 = -650 to -700 µV/K and a low and temperature-stable thermal conductivity of k = 2 to 2.2 W/mK in the temperature range of 300 to1000 K. First-principles electronic structure calculations are used to link the temperature dependence of the Seebeck coefficient measured experimentally to the evolution of the density of states with temperature and indicate possible avenues for its further optimization through electron doping and control of the A-site occupancies. Moreover, lattice thermal conductivity calculations give an insight into the dependence of the thermal conductivity on specific crystallographic directions of the material, which could be exploited via nano-structuring to create high-efficiency compound thermoelectrics.

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