Physical Properties of Oxide Thermoelectric Materials Prepared by the Polymerized Complex Method

本研究采用聚合络合法制备了微观结构可控的氧化物热电材料，并对其物理性能进行了测试。一般认为聚合络合法是制备各种氧化物材料的简便方法。我们研究了Zn_<1-x>Al_xO和层状Na_xCo_2 O_4体系。将化学计量量的金属硝酸盐水合物和柠檬酸溶解在乙二醇中。将溶液浓缩并形成粘性聚合复合物。这些聚合物产物在空气中分解成细而均匀的粉末。Zn_<1-x>Al_xO系粉末在1100℃、10 ~ 30 MPa、10 min条件下用SPS（Spark Plasma Sintering）烧结，Na_xCo_2O_4系粉末在25 MPa、900℃、1 ~ 2 h条件下热压烧结。用X射线衍射法对样品进行了物相鉴定， ...更多信息 使用SEM检查样品的显微结构。测量了样品的塞贝克系数、电阻率和热导率等物理性能。聚合<1-x>络合法制备的Zn_ Al_xO的晶粒尺寸约为1 ~ 2μm，比传统固相反应法制备的Zn_ Al_xO的晶粒尺寸（10μm）小得多。Zn 1-xAlxO的Seebeck系数和电阻率的绝对值一般随x的Al含量的增加而减小。在Al含量一定的条件下，聚合络合法和固相反应法制备的样品的上述值相比，聚合络合法制备的样品的上述值较小。这些样品的热导率几乎没有差异，尽管前者的晶粒尺寸要小得多。这些结果表明，聚合络合法制备的样品更均匀，更容易实现载体的掺杂到材料中。另一方面，聚合络合物法制备的NaxCo 2 O 4陶瓷显示出比固相反应法更高的晶体各向异性，并具有较低的电阻率，保持适度的塞贝克系数。结果表明，聚合络合法制备的样品具有较大的品质因数。少

In this Study we have prepared the oxide thermoelectric materials with controlled microscopic structure by the polymerized complex method, and measured their physical properties. It is generally considered that the polymerized complex method is a convenient method for preparing various oxide materials. We have investigated the Zn_<1-x>Al_xO and Layered-Na_xCo_2O_4 systems. Stoichiometric amounts of metal nitrate hydrate and citric acid were dissolved in ethylene glycol. The solution was concentrated and the viscous polymerized complexes were formed. These polymeric products were decomposed to a fine and uniform powder in air. In the case of Zn_<1-x>Al_xO system the obtained powder was sintered by SPS (Spark Plasma Sintering) apparatus at 1100℃ for 10min at a pressure of 10〜30MPa, while in the case of Na_xCo_2O_4 system the obtained powder was sintered by Hot-Pressing at 900℃ for 1〜2h at a pressure of 25MPa. The phase identification of the samples was made by X-ray diffraction and the m … More icroscopic structure of the samples was examined using SEM. The physical properties such as Seebeck coefficient, the electrical resistivity and thermal conductivity of the samples were measured. The crystal grain size of Zn_<1-x>Al_xO prepared by the polymerized complex method is about 1〜2μm, which is much smaller than that by the conventional solid state reaction method, 10μm. The absolute value of the Seebeck coefficient and the electrical resistivity for Zn1-xAlxO generally decreases with increasing Al content of x. Comparing theses values at fixed Al content between the samples prepared by the polymerized complex and solid state reaction methods, the samples by the polymerized complex method have smaller values. There is almost no difference in the thermal conductivity between these samples, although the crystal grain size of the former is much smaller. These results indicate that the more homogeneous samples were obtained by the polymerized complex method and the doping of the carrier into the material can be more easily realized in the samples prepared by the polymerized complex method. On the other hand, NaxCo2O4 ceramics prepared by the polymerized complex method show higher crystallographic anisotropy than that by the solid state reaction method, and have lower electrical resistivity maintaining moderate Seebeck coefficient. As a result, lager figure of merit was obtained on the samples prepared by the polymerized complex method. Less