Role of phonon scattering by elastic strain field in thermoelectric Sr{sub 1−x}Y{sub x}TiO{sub 3−δ}
- Department of Materials Science and Engineering, Clemson University, Clemson, South Carolina 29634 (United States)
- Department of Physics and National Center for Physical Acoustics, University of Mississippi, University, Mississippi 38677 (United States)
- Electron Microscope Facility, Clemson Research Park, Clemson University, Clemson, South Carolina 29625 (United States)
- Materials Science and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900 (Saudi Arabia)
Perovskite-type SrTiO{sub 3−δ} ceramics are multifunctional materials with significant potential as n-type thermoelectric (TE) materials. The electronic and thermal transport properties of spark plasma sintered polycrystalline Sr{sub 1−x}Y{sub x}TiO{sub 3−δ} (x = 0.05, 0.075, 0.1) ceramics are systematically investigated from (15–800) K. The Sr{sub 0.9}Y{sub 0.1}TiO{sub 3−δ} simultaneously exhibits a large Seebeck coefficient, α > −80 μV/K and moderately high electrical resistivity, ρ ∼ 0.8 mΩ-cm at a carrier concentration of ∼10{sup 21} cm{sup −3} at 300 K resulting in a high TE power factor defined herein as (α{sup 2}σT) ∼ 0.84 W/m-K at 760 K. Despite the similar atomic masses of Sr (87.6 g/mol) and Y (88.9 g/mol), the lattice thermal conductivity (κ{sub L}) of Sr{sub 1−x}Y{sub x}TiO{sub 3−δ} is significantly reduced with increased Y-doping, owing to the smaller ionic radii of Y{sup 3+} (∼1.23 Å, coordination number 12) compared to Sr{sup 2+} (∼1.44 Å, coordination number 12) ions. In order to understand the thermal conductivity reduction mechanism, the κ{sub L} in the Sr{sub 1−x}Y{sub x}TiO{sub 3−δ} series are phenomenologically modeled with a modified Callaway's equation from 30–600 K. Phonon scattering by elastic strain field due to ionic radii mismatch is found to be the prominent scattering mechanism in reducing κ{sub L} of these materials. In addition, the effect of Y-doping on the elastic moduli of Sr{sub 1−x}Y{sub x}TiO{sub 3−δ} (x = 0, 0.1) is investigated using resonant ultrasound spectroscopy, which exhibits an anomaly in x = 0.1 in the temperature range 300–600 K. As a result, the phonon mean free path is found to be further reduced in the Sr{sub 0.9}Y{sub 0.1}TiO{sub 3−δ} compared to that of SrTiO{sub 3−δ}, resulting in a considerably low thermal conductivity κ ∼ 2.7 W/m-K at 760 K. Finally, we report a thermoelectric figure of merit (ZT) ∼ 0.3 at 760 K in the Sr{sub 0.9}Y{sub 0.1}TiO{sub 3−δ}, the highest ZT value reported in the Y-doped SrTiO{sub 3} ceramics thus far.
- OSTI ID:
- 22304136
- Journal Information:
- Journal of Applied Physics, Vol. 115, Issue 22; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ATOMIC RADII
CARRIERS
CERAMICS
COORDINATION NUMBER
DOPED MATERIALS
ELECTRIC CONDUCTIVITY
EQUATIONS
MASS
MEAN FREE PATH
PEROVSKITE
PHONONS
PLASMA
POLYCRYSTALS
POWER FACTOR
SCATTERING
SPECTROSCOPY
STRAINS
STRONTIUM TITANATES
THERMAL CONDUCTIVITY
YTTRIUM ADDITIONS