Abstract
Typical mean free path (MFP) of electron in oxides stays lower than 10 nm, while FP of phonon widely disperses in the range of 5-1000 nm. Such MFP gap enables to engineer thermoelectric properties, namely enhancing figure of merit via reduction in thermal conductivity (k) taking along with moderate increase in resistivity (r). Here, we demonstrate the MFP gap strategy in Zr doped In2O3 by tuning boundary scattering (BS). Employed range of the BS was 20-2000 nm, which was manipulated by grain size (L) of the ceramics with relative density higher than 90%. It was confirmed that the variation of k well agreed with Debye-Callaway model in which L was incorporated as FP of BS, while increase in r caused by the BS reasonably followed the Boltzmann equation assuming energy-independent scattering, i.e., MFP=L. Above formalism along with the expression of Seebeck coefficient by the Boltzmann equation offers a methodology for the optimization of MFP by the BS.
