Si含量对高锰硅化合物相组成及热电性能的影响研究

采用高频感应熔融、退火结合放电等离子烧结方法制备高锰硅(HMS)化合物MnSi1.70+x(x=0,0.05,0.1,0.15),系统研究了Si含量变化对材料相组成、微结构和热电性能的影响规律.结果表明,当x0.1时,样品由HMS和贫Si的MnSi金属相两相组成,随着Si含量x的增加,MnSi相相对含量减小;当x=0.1时,所得样品为单相HMS化合物;当x0.1时,样品由HMS和过量Si两相组成.随着x的增加,由于样品中高电导的金属相MnSi含量逐渐减少,样品的电导率逐渐下降,而Seebeck系数随之增加.室温下样品载流子浓度和有效质量随x增大逐渐减小,而迁移率逐渐增加.MnSi和Si杂相与HMS相比均为高热导相,因此当x=0.1时,由于样品为单相HMS,从而表现出最低热导率和最高ZT值.MnSi1.80样品在800K时热导率最小值达到2.25W·m-1K-1,并在850K处获得最大ZT值(0.45).

Effects of Si content on phase composition and thermoelectric properties of higher manganese silicide

MnSi_1.70+x(x=0, 0.05, 0.1, 0.15) compounds have been prepared by induction melting-annealing procedure combined with spark plasma sintering method. The phase composition and the thermoelectric properties of higher manganese silicide (HMS) with different Si contents are investigated. The results indicate that the samples with x＜0.1 include HMS phase and MnSi phase, and the relative content of MnSi phase decreases with x value increasing. The sample with x=0.1 is single phase HMS. The phase compositions of the sample with x＞0.1 are HMS and Si. As x value inereases the electrical conductivity of the sample gradually decreases, while the Seebeck coefficient increases because metallic MnSi phase decreases. The carrier concentration and the effective mass of the sample at room temperature decrease and the carrier mobility increases with x value increasing. In the sample with x=0.1, the impurity phase content is the least, which results in the lowest thermal conductivity and a minimum value of 2.25 W ·m^-1K^-1 at 800 K. The maximum ZT value of 0.45 is obtained at 850 K for MnSi_1.80.