American Institute of Physics, APL Materials, 2(1), p. 021101
DOI: 10.1063/1.4818356
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We propose a novel route for optimizing the thermoelectric power of a polaronic conductor, independent of its electronic conductivity. This mechanism is exemplified here in thin-films of La2NiO4+δ. Tensile stress induced by epitaxial growth on SrTiO3 doubles the thermoelectric power of ≈15 nm thick films relative to ≈90 nm films, while the electronic conductivity remains practically unchanged. Epitaxial strain influences the statistical contribution to the high temperature thermopower, but introduces a smaller correction to the electronic conductivity. This mechanism provides a new way for optimizing the high temperature thermoelectric performance of polaronic conductors.