Improved thermoelectric properties of La_1-xSr _xCoO₃ nanowires

Nanotechnology has brought novel and controllable thermoelectric (TE) characteristics to conventional materials. Here we report a simple method to synthesize single-crystalline La_1-xSr_xCoO₃ nanowire compacts with an improved TE efficiency. The figure of merit ZT in the nanowires can reach 0.19 at 300 K, which is nearly twice that in the bulk, and this room-temperature ZT is very high among oxide materials. The enhancement of TE efficiency can be attributed to both extrinsic and intrinsic factors: First, the unique nanowire structure together with numerous interfaces in the compact samples strongly suppresses the phonon thermal transport. Second, the small dimensions of nanowires give rise to an unexpected increase in the thermopower due to a reduction of the effective bandwidth and variation of the electron configuration. Our results indicate that the TE response of conventional oxides can be effectively improved by the form of nanowires, which can be synthesized much easier than single crystals and epitaxial thin films.