Journal
JOURNAL OF APPLIED PHYSICS
Volume 114, Issue 24, Pages -Publisher
AMER INST PHYSICS
DOI: 10.1063/1.4854475
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Funding
- Competence Centre Energy and Mobility
- Swiss Federal Office of Energy (BfE)
- Empa
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Polycrystalline tungsten-substituted CaMn1-xWxO3-delta (0.00 <= x <= 0.05) powders were synthesized from a polymeric precursor, pressed and sintered to high density. The impact of tungsten substitution on the crystal structure, thermal stability, phase transition, electronic and thermal transport properties is assessed. Tungsten acts as an electron donator and strongly affects high-temperature oxygen stoichiotnetry. Oxygen vacancies form in the high figure-of-merit (ZT)-region starting from about T = 1000 K and dominate the carrier concentration and electronic transport far more than the tungsten substitution. The analysis of the transport properties yields that in the investigated regime the band filling is sufficiently high to overcome barriers of polaron transport. Therefore, the Cutler-Mott approach describes the electrical transport more accurately than the Mott approach for small polaron transport. The lattice thermal conductivity near room temperature is strongly suppressed with increasing tungsten concentration due to mass-difference impurity scattering. A ZT of 0.25 was found for x = 0.04 at 1225 K. (C) 2013 AIP Publishing LLC.
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