用低温固相反应制备p型Mg_2Si基热电材料

PREPARATION OF Mg_(2)Si BASED pTYPE THERMOELCTRIC MATERIAL BY SOLID STATE REACTION AT LOW TEMPERATURE

用Mg粉和Si粉通过固相反应在823K时保温8h合成了Mg2Si粉末;并通过外加Ag粉用二次固相反应在相同条件下合成了Mg2Si基热电固溶体。采用放电等离子烧结法(SPS),以掺杂Ag后的固溶体为原料制备出了p型Mg2Si基热电材料。研究了Ag掺杂量对Mg2Si材料热电性能的影响。结果表明:随着掺杂Ag的摩尔分数的增大,材料的Seebeck系数(即温差电动势)和电导率均有增大的趋势,但热导率变化不大。温度为513K时,掺杂Ag的摩尔分数为15×10-3的试样的优值系数Z值和优值系数与温度之积ZT均为最大,分别为18.2×10-6/K和0.01。

Mg_(2)Si powder without any impurity was synthesized by solid state reaction at 823 K for 8 h using Mg and Si powders as raw materials. Mg_(2)Si-based thermoelectric solid solution powder with doping Ag powder was prepared by the same method. Mg_(2)Si-based thermoelectric material was prepared by spark plasma sintering (SPS) from the solid solution powder doped with Ag powder. The influence of doping content of Ag on the electrical properties of the thermoelectric material was investigated. Results indicate that with the increasing of Ag content, the Seebeck coefficient and electrical conductivity show an increasing tendency, but there is no evident change for thermal conductivity. The values of Z (figure of merit) and ZT (T is temperature) of the samples doped with 15×10^(-3) (molar fraction) Ag are optimal at the temperature of 513 K, 18.2×10^(-6) /K and 0.01 respectively.