Thermomigration and Soret effect in Na x CoO2 as thermoelectric material: Preparation and characterization of sodium cobaltate thin films
| Autor: | Christian Schneider, Jürgen Janek, Patrick Schichtel, Boris Mogwitz, Kerstin Volz, Andreas Beyer, Rainer Straubinger, Marcus Rohnke |
|---|---|
| Rok vydání: | 2015 |
| Předmět: |
Chemistry
Diffusion Sodium chemistry.chemical_element 02 engineering and technology Surfaces and Interfaces 010402 general chemistry 021001 nanoscience & nanotechnology Condensed Matter Physics Thermoelectric materials 01 natural sciences Thermophoresis 0104 chemical sciences Surfaces Coatings and Films Electronic Optical and Magnetic Materials Pulsed laser deposition chemistry.chemical_compound Chemical engineering Lanthanum aluminate Materials Chemistry Sapphire Electrical and Electronic Engineering Thin film 0210 nano-technology |
| Zdroj: | physica status solidi (a). 213:1284-1295 |
| ISSN: | 1862-6300 |
| Popis: | Sodium cobaltate (NaxCoO2, NCO) is a model type thermoelectric material for high temperature applications, which is representative for the class of non-stoichiometric and mixed ion-electron conducting thermoelectrics (e.g., Cu2 – xSe). The present study deals with the kinetic instability of the originally homogeneous chemical composition when a temperature gradient is applied – a common situation in thermoelectric materials with a mobile component (element), but rarely considered in thermoelectric materials research so far. In order to investigate a well reproducible system, highly epitaxial thin films of NaxCoO2 with an atmosphere protective capping layer of alumina are prepared via pulsed laser deposition on sapphire (001) and lanthanum aluminate (111). A self-designed non-isothermal set-up allows the precise determination of the heat of transport for mobile sodium as 8.3 kJ mol−1 and, therefore, the quantification of thermodiffusion (i.e., the Ludwig-Soret effect in the stationary state). The experiments also allow to estimate the chemical diffusion coefficient of sodium at 422 K as about = 5 × 10−4 cm2 s−1. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|
Plný text