机械合金化法制备Fe_(0.95)Co_(0.05)Si_2材料及其热电性能

Preparation of Fe_(0.95)Co_(0.05)Si_2 Material by Mechanical Alloying and Its Thermoelectric Properties

采用机械合金化结合真空烧结法制备了掺钴的N型β-FeSi_2热电材料Fe_(0.95)Co_(0.05)Si_2,利用XRD和SEM分析了该材料的物相组成和显微形貌,对机械合金化粉体进行了DSC分析,并对烧结试样进行了热电性能测试。结果表明:球磨5 h后铁、钴、硅混合物可完全合金化,全部生成β-FeSi_2、α-Fe_2Si_5和ε-FeSi相;随着球磨时间延长,合金粉体更加均匀细小,β-FeSi_2的含量逐渐增加;机械合金化20 h的粉体压制后经过1 373 K烧结2 h和1 073 K烧结2 h,可获得单相β-FeSi_2材料;合金粉体在1 177 K开始分解;随着温度升高,Fe_(0.95)Co_(0.05) Si_2试样的Seebeck系数α、电导率σ增大,热导率K降低,而无量纲热电优值明显增大,在773 K时最大,为0.11。

N-type β-FeSi2 thermoelectric material Fe0.95Co0.05Si2 deped with Co was prepared by mechanical alloying and vacuum sintering. XRD and SEM were applied to analyze the phase composition and microstructure of the material, and the powders prepared by mechanical alloying were analyzed by DSC. The thermoelectric properties of the sintered samples were tested. The results show that the mixed powders of Fe, Co and Si had been fully alloyed after milling for 3 h. The formed phases were alloy phases composed of β-FeSi2,α-Fe2Si5 and ε-FeSi. With the extension of milling time, aIloy powders became more homogeneous and smaller, and the content of β-FeSi2 gradually increased. However, a single-phase β-FeSi2 could be obtained by mechanical alloying for 20 h and sintering at 1 373 K for 2 h and 1 073 K for 2 h. The alloy powders began to decompose at 1 177 K. With the increase of temperature, Seebeck coefficient α and electric conductivity a of the Fe0.95Co0.05Si2 sample increased while thermal conductivity κ decreased, which led to the maximum dimensionless thermoelectric figure merit of 0. 11 was obtained at 773 K.