Thermomigration and Soret effect in NaxCoO2 as thermoelectric material: Preparation and characterization of sodium cobaltate thin films
Thermomigration and Soret effect in NaxCoO2 as thermoelectric material: Preparation and characterization of sodium cobaltate thin films
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NaxCoO2 热电材料的热迁移和 Soret 效应：钴酸钠薄膜的制备和表征
DOI：
10.1002/pssa.201532725
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
J. Janek
中科院分区：
文献类型：
--
作者：
C. Schneider;Patrick Schichtel;B. Mogwitz;R. Straubinger;A. Beyer;M. Rohnke;K. Volz;J. Janek
钴酸钠（NaxCoO 2，NCO）是用于高温应用的模型型热电材料，其代表非化学计量和混合离子-电子传导热电体（例如，Cu 2- xSe）。本研究涉及的动力学不稳定性的原始均匀的化学成分时，施加温度梯度-一种常见的情况下，在热电材料的移动的组件（元素），但很少考虑在热电材料的研究到目前为止。为了研究一种可重复性好的系统，通过脉冲激光沉积在蓝宝石（001）和铝酸镧（111）上制备了具有氧化铝气氛保护盖层的NaxCoO 2的高度外延薄膜。自行设计的非等温装置可以精确测定移动的钠的迁移热为8.3 kJ mol−1，因此可以定量热扩散（即，在静止状态下的Ludwig-Soret效应）。实验还可以估计钠在422 K时的化学扩散系数约为D <$Na = 5 × 10−4 cm 2 s−1。
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 D˜Na = 5 × 10−4 cm2 s−1.