Ge取代P型高锰硅合金的晶粒细化及其热电性能

Thermoelectric Properties and Grain Refinement of Ge-substituted P-type Higher Manganese Silicide Alloy

采取悬浮熔炼法制备Ge取代的高锰硅试样Mn(Si1-xGex1).733(x取0.004,0.006,0.008,0.010,0.012),采用甩带法得到快凝高锰硅合金粉末,XRD分析表明快速凝固能够减少MnSi金属相的含量,Ge对Si位的取代产生晶格畸变,使得衍射峰向低角区偏移;将悬浮熔炼和快速凝固所得试样进行放电等离子烧结,测试并比较其热电性能。结果显示,快速凝固有效地降低了材料的热导率,Ge取代则使得有效载流子浓度增加,提高了电导率,从而提高材料的热电性能。实验范围内,当Ge取代量x=0.010时,ZT值最高,悬浮熔炼试样在850K时ZT值为0.53,快速凝固试样在750K时ZT值达到0.55。

Levitation melting was adopted to prepare Ge-substituted higher manganese silicide（HMS） thermoelectric Mn（Si1-xGex）1.733（x=0.004,0.006,0.008,0.010,0.012） alloys.Rapidly solidified HMS alloy powders were obtained by melt spinning to refine grain sizes.The X-ray diffraction（XRD） patterns showed that rapid solidification could reduce the content of MnSi metallic phase.Lattice distortion was produced by the substitution of Ge for Si,rendering a gradual shift of diffraction peaks to low-angle side in XRD patterns.Spark plasma sintering（SPS） was employed to prepare high density bulk alloy samples from both the levitation melted powder and the melt-spun powder.Thermoelectric performances of these samples were measured and compared.Results revealed that the thermal conductivity decreased in melt-spun samples and the electrical conductivity increased because of Ge doping.Optimization in these two aspects would enhance the dimensionless figure of merit ZT.Within the range of Ge substitution ratios in the experiment,the highest ZT value has been obtained when x=0.010.For the levitation melted samples,the maximum ZT value was 0.53 at 850K,and for the melt-spun samples,0.55 at 750K.