【作者】 龙海山；

【导师】 姜洪义；

【作者基本信息】 武汉理工大学 ， 材料学， 2004， 硕士

【摘要】 本文首先对热电现象、热电材料的发展历史以及Mg₂Si基热电材料的研究进展作了比较详细的综述。已有的研究表明，以Mg₂Si为基、通过掺杂得到的固溶体是优秀的中温区（400-700K）热电半导体材料。 本文应用热力学理论对Mg₂Si制备过程进行了讨论，并探讨了固相反应进行的可能性及工艺制度的确立。结果表明在该体系中，可以通过低温固相反应合成Mg₂Si化合物粉末，同时在体系中MgO是非常容易生成，这主要是因为Mg在较高温度下容易挥发并与残留在反应容器内的O₂进行反应的结果，同时在降温过程中Mg₂Si也容易被氧化。MgO对材料的热电性能是极其有害的，为此必须对制备工艺进行优化和改进，尽量避免MgO的生成。 本文选择Ag元素作为掺杂元素，通过二次固相反应制备出p型Mg₂Si基热电材料。研究结果表明，用低温固相反应可以在制得Mg₂Si粉末的基础上掺杂而对纯Mg₂Si的热电性能进行改进。随着掺杂量的增大，材料的Seebeck系数有所增大，电导率增加明显，而热导率没有明显的变化。掺杂Ag浓度为15000ppm样品的Z值和ZT值均为最大，分别为18.2×10^-6K^-1和0.01。 本文选择了纳米BN粉以改变Mg₂Si基热电材料的热电性能。研究结果表明，当在Mg₂Si基热电材料中掺杂少量的BN纳米粉后，即可以使材料的热导率降低很多，同时也会使材料的电导率有所降低。但整体看来，掺杂少量的BN纳米粉对材料的热电性能是有利的。更多还原

【Abstract】 This paper have reviewed detailed the thermoelectricity, the history of thermoelectric materials and the current situation of Mg2Si based thermoelectric material. The studies in existence showed that the solid solutions which based with Mg2Si and doped with other elements are good thermoelectric semiconductors working at mid-temperature (400-700K).The basic thermodynamic theory was introduced to calculate the Gibbs function changes of Mg-Si-0 system and was used to discuss the process of synthesizing the Mg2Si powder. The probability of synthesizing the Mg2Si powder by solid-state reaction at low temperature and the techniques were confirmed. The result showed that the Mg2Si powder could be synthesized by solid-state reaction at low temperature but in the system the impurity of MgO appeared easily. It is because of that the element of Mg is very active and it would react with the rudimental O2 in the container and at the same time the Mg2Si could be oxide when the temperature descending. The techniques of solid-state reaction must be mended because the MgO is one of the impurities that could deduce the thermoelectric properties.Ag was selected for dopant in Mg2Si synthesizing process. The influence of dopants amount on thermoelectric properties of Mg2Si specimen was researched. The p-type Mg2Si based thermoelectric materials was synthesized first time by solid-state reaction. The result showed that when the dopants amount is increasing, the Seebeck coefficient and the electrical conductivity of samples are increasing too, but the thermal conductivity has not an obvious change. Z and ZT of specimen doped with 15000ppm Ag are the largest, and the values are 18.2 X 10-6 K-1 and 0.01 respectively.The nono-powder of BN was selected to change the thermoelectric properties of Mg2Si based thermoelectric materials. The result shows thatwhen the powder of BN was doped in the Mg2Si based thermoelectric materials, the thermal conductivity of sample is decrease obviously, and the electrical conductivity is decreasing at the same time. The doping with a little BN powder is favorableness for the Mg2Si based thermoelectric materials’ thermoelectric properties.更多还原