n型Bi_(2)Te_(3-x)Se_(x)纳米结构材料的制备及热电性能

Preparation and thermoelectric properties of n-type Bi_(2)Te_(3-x)Se_(x) nanostructured materials

采用蒸发冷凝法将块体Bi、Te及Se制备成单质纳米粉末,将单质纳米粉末按照Bi_(2)Te_(3)-xSex化学计量后充分混合后进行机械合金化。将合金化的粉末采用微波烧结技术烧结制得具有纳米结构的块体材料,对其微结构和热电性能进行了表征分析。研究表明,烧结块体由单一物相组成,材料内部具有层状微结构并且存在大量晶粒尺度为50~100 nm的细小晶粒构成的纳米结构。随着Se含量的增加,烧结块体的电输运特性由半导体转变为金属,纳米结构的形成有效降低了热导率,有利于材料热电性能的提升,当x=0.20时,Bi_(2)Te_(2.80)Se_(0.20)样品在423K附近获得最大的ZT值为0.85。

The bulk of Bi,Te and Se were prepared into nanopowder by evaporation condensation method,and the Bi_(2)Te_(3-x)Se_(x) alloy powder was obtained after mechanical alloying of the nanopowder.The alloy powder was sintered using microwave sintering technology to obtain a nanostructured bulk material,and its microstructure and thermoelectric properties were characterized and analyzed.The sintered samples are composed of a single phase.The materials have a layered microstructure and the nanostructures composed of large number of fine grains with grain sizes of 50-100 nm.With the increase of Se content,the electrical transport characteristics of sintered samples change from semiconductors to metals,and the formation of nanostructures effectively reduces thermal conductivity,which is conducive to the improvement of thermoelectric properties.When the Se content x=0.20,the Bi_(2)Te_(2.80)Se_(0.20) sample achieves a maximum ZT value of 0.85 near 423K.