Strain-induced enhancement of the thermoelectric power in thin films of hole-doped La2NiO4+δ

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+delta. Tensile stress induced by epitaxial growth on SrTiO3 doubles the thermoelectric power of approximate to 15 nm thick films relative to approximate 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. (C) 2013 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.