Phonon-Glass and Heterogeneous Electrical Transport in A-Site Deficient SrTiO3

Srinivasa R. Popuri, Rodolphe Decourt, Jason A. McNulty, Michael Pollet, Andrew Dominic Fortes, Finlay D. Morrison, Mark S. Senn, Jan-Willem Gezienes Bos

Research output: Contribution to journalArticle

Abstract

The phonon-glass electron crystal concept is one of the key guiding principles for the development of efficient thermoelectric materials. Here, we confirm that SrTiO 3 becomes a phonon-glass for large numbers of A-site vacancies in the Sr 1-x La 0.67x0.33x TiO 3 series and show that its electron crystal properties are stymied by the presence of a core-shell grain structure. Thermal conductivity, heat capacity, and neutron powder diffraction, complemented by representational analysis and phonon calculations, were used to investigate the thermal transport. This reveals that the heat carrying modes are dominated by Sr motions and that these become more localized upon the introduction of the A-site vacancies, consistent with the observed phonon-glass state. Impedance spectroscopy and direct current electrical measurements were used to probe the electrical properties of insulating and conducting samples. This reveals the coring of grains due to oxidation on cooling from sintering temperatures. The resultant insulating shell limits the thermoelectric power factor to S 2 /ρ = 0.45 mW m -1 K -2 and the figure-of merit to ZT = 0.15 at 900 K for Sr 0.20 La 0.530.27 Ti 0.95 Nb 0.05 O 3?δ . The thermal properties of these materials are, therefore, controlled by an intrinsic feature of the microstructure (i.e., the A-site vacancies), whereas the electrical properties are grain boundary limited, which in principle can be controlled independently to raise S 2 /ρ and ZT.

Original languageEnglish
Pages (from-to)5198–5208
Number of pages11
JournalJournal of Physical Chemistry C
Volume123
Issue number9
Early online date4 Feb 2019
DOIs
Publication statusPublished - 7 Mar 2019

Fingerprint

Vacancies
Glass
glass
Electric properties
electrical properties
Shells (structures)
Crystals
Neutron powder diffraction
thermoelectric materials
Electrons
Crystal microstructure
Thermoelectric power
figure of merit
electrical measurement
Specific heat
crystals
Thermal conductivity
sintering
Grain boundaries
electrons

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

Cite this

Popuri, S. R., Decourt, R., McNulty, J. A., Pollet, M., Fortes, A. D., Morrison, F. D., ... Bos, J-W. G. (2019). Phonon-Glass and Heterogeneous Electrical Transport in A-Site Deficient SrTiO3. Journal of Physical Chemistry C, 123(9), 5198–5208. https://doi.org/10.1021/acs.jpcc.8b10520
Popuri, Srinivasa R. ; Decourt, Rodolphe ; McNulty, Jason A. ; Pollet, Michael ; Fortes, Andrew Dominic ; Morrison, Finlay D. ; Senn, Mark S. ; Bos, Jan-Willem Gezienes. / Phonon-Glass and Heterogeneous Electrical Transport in A-Site Deficient SrTiO3. In: Journal of Physical Chemistry C. 2019 ; Vol. 123, No. 9. pp. 5198–5208.
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Popuri, SR, Decourt, R, McNulty, JA, Pollet, M, Fortes, AD, Morrison, FD, Senn, MS & Bos, J-WG 2019, 'Phonon-Glass and Heterogeneous Electrical Transport in A-Site Deficient SrTiO3', Journal of Physical Chemistry C, vol. 123, no. 9, pp. 5198–5208. https://doi.org/10.1021/acs.jpcc.8b10520

Phonon-Glass and Heterogeneous Electrical Transport in A-Site Deficient SrTiO3. / Popuri, Srinivasa R.; Decourt, Rodolphe; McNulty, Jason A.; Pollet, Michael; Fortes, Andrew Dominic; Morrison, Finlay D.; Senn, Mark S.; Bos, Jan-Willem Gezienes.

In: Journal of Physical Chemistry C, Vol. 123, No. 9, 07.03.2019, p. 5198–5208.

Research output: Contribution to journalArticle

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AU - Popuri, Srinivasa R.

AU - Decourt, Rodolphe

AU - McNulty, Jason A.

AU - Pollet, Michael

AU - Fortes, Andrew Dominic

AU - Morrison, Finlay D.

AU - Senn, Mark S.

AU - Bos, Jan-Willem Gezienes

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AB - The phonon-glass electron crystal concept is one of the key guiding principles for the development of efficient thermoelectric materials. Here, we confirm that SrTiO 3 becomes a phonon-glass for large numbers of A-site vacancies in the Sr 1-x La 0.67x → 0.33x TiO 3 series and show that its electron crystal properties are stymied by the presence of a core-shell grain structure. Thermal conductivity, heat capacity, and neutron powder diffraction, complemented by representational analysis and phonon calculations, were used to investigate the thermal transport. This reveals that the heat carrying modes are dominated by Sr motions and that these become more localized upon the introduction of the A-site vacancies, consistent with the observed phonon-glass state. Impedance spectroscopy and direct current electrical measurements were used to probe the electrical properties of insulating and conducting samples. This reveals the coring of grains due to oxidation on cooling from sintering temperatures. The resultant insulating shell limits the thermoelectric power factor to S 2 /ρ = 0.45 mW m -1 K -2 and the figure-of merit to ZT = 0.15 at 900 K for Sr 0.20 La 0.53 → 0.27 Ti 0.95 Nb 0.05 O 3?δ . The thermal properties of these materials are, therefore, controlled by an intrinsic feature of the microstructure (i.e., the A-site vacancies), whereas the electrical properties are grain boundary limited, which in principle can be controlled independently to raise S 2 /ρ and ZT.

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Popuri SR, Decourt R, McNulty JA, Pollet M, Fortes AD, Morrison FD et al. Phonon-Glass and Heterogeneous Electrical Transport in A-Site Deficient SrTiO3. Journal of Physical Chemistry C. 2019 Mar 7;123(9):5198–5208. https://doi.org/10.1021/acs.jpcc.8b10520