Bi_2Te_(2.55)Se_(0.45)合金熔体电阻率及凝固与熔体状态相关性的探索

Study on the Correlation Between Melt States and Resistivity and Solidification of Bi_2Te_(2.55)Se_(0.45)Alloy

探索了Bi2Te2.55Se0.45热电材料熔体的电阻率温度行为,并在此基础上,采用热分析法、金相分析、x射线衍射、SEM和EDS等表征手段研究了不同熔体状态对Bi2Te2.55Se0.45合金凝固行为和组织的影响.结果所示,Bi2Te2.55Se0.45合金熔体升温过程中在840～940℃的范围内存在温度诱导不可逆液-液结构转变.凝固结果表明,熔体结构转变后合金熔体的凝固行为和组织与转变前熔体的凝固情况有明显差别,如形核和生长过冷度分别增加了17.6℃和2.2℃,形核率明显提高,凝固时间缩短了8s,凝固组织明显细化,且分布更为均匀;此外,熔体状态的改变使合金XRD特征峰向高角度偏移,沿（001）晶面的择优取向明显减弱.

Abstract： The behaviors of electrical resistivity of liquid n-type Bi2Te2ssSea45 thermoelectric alloys were explored. And on this basis, thermal analysis, XRD, metallographic analysis, SEM and EDS were utilized to investigate the effects of different melt states on the behaviors and structure of solidification of Bi2Te22.25Se0.45 alloy. The results show that temperature induced irreversible liquid-liquid structure transition occur in the liquid alloy of Bi2Te2.55Se0.45 at the temperature from 840 ~C to 940℃ during heating process. The result of solidification experiments indicated that the melt structure transition had a remarkable effect on the solidification, i.e. the undercooling degrees of nucleation and growth was increased by 17.6℃ and 2.2℃ , respectively, the solidification time shortened 8 s, the solidification microstructures were refined obviously. Moreover, the characteristic peak lightly shifts to high-angle after structure transition, and the preferential orientation of （001） planes was weakened.