Progress of high efficiency thermoelectric oxide ceramic materials generated at high temperature

1.高温霍尔系数测量装置的试制该装置可以在不同的氧分压下测量高达1000ﾟC的霍尔系数。因为单独测量载流子浓度和迁移率对于了解材料在高温下的导电机理是必不可少的。采用常规烧结方法制备了厚度为0.3~0.4 mm的盘状样品，并将其成形为三叶草状。用van der Pauw方法测量了(La，Sr)FeO_3的霍尔系数。在两个磁场方向下分别采用正、负电流方向进行测量，以消除样品形状的影响。Sb掺杂BaSnO_3的热电性能锡替代Sb使BaNO_3的电导率从10^~(-8)提高到10^~2 S/cm。在Ta、Nb、Sb中，Sb是改善电导率最有效的替代材料。从电导率和Seebeck系数的测量结果可以看出，Sb掺杂BaSnO_3的导电机制在500ﾟC以下是由杂质原子引起的非本征导电，而在500ﾟC以上则是本征导电。具有较高温差电势的材料的研究温差电势的大小是电导率与塞贝克系数的乘积。塞贝克系数的研究对于研究具有较高温差电势的材料具有重要意义。因此，不仅需要了解载流子浓度，而且还需要了解散射因子和态密度。

1.Trial manufacture of an apparatus for the measurement of Hall coefficient at high temperature The apparatus was trial manufactured for the measurement of Hall coefficient up to 1000 ﾟC under various oxygen partial pressure. Because the individual measurement of carrier concentration and the mobility is essential for the understanding of the conductive mechanism of the material at high temperature. The disc-shape sample with 0.3-0.4 mm in thickness was prepared by conventional sintering methods and was shaped into like a clover. The Hall coefficient of (La,Sr)FeO_3 was measured by van der Pauw methods. The measurement was performed by positive and negative current direction under the two magnetic field direction to cancel the effect of sample shape,.2. The thermoelectric power of Sb doped BaSnO_3 The electrical conductivity of BaSnO_3 increased from 10^<-8> to 10^2 s/cm by substitution of Sn to Sb. Among Ta, Nb and Sb, Sb is the most effective substitute material for the improvement of the electrical conductivity. From the results of electrical conductivity and Seebeck coefficient measurements, it was clarified that the conduction mechanism of Sb doped BaSnO_3 was extrinsic conduction caused by impurity atom up to 500ﾟC, and was intrinsic one above 500ﾟC. From the result of the present study, it will be expected that this material has high thermoelectric power at higher temperature.3. Research of the materials with higher thermoelectric power The degree of thermoelectric power is the product of electrical conductivity by Seebeck coefficient. The investigation of the Seebeck coefficient will be more important for the research of the materials with higher thermoelectric power. Therefore the understanding of not only the carrier concentration but also the scattering factor and density of the states will be necessary.