退火对高压烧结Gd掺杂Bi_2Te_(2.7)Se_(0.3)纳米晶热电性能的影响

Effects of Annealing Temperature on Bi_2Te_(2.7)Se_(0.3) Doped with Gd Fabricated by High Pressure Sintering

以Bi粉、Te粉、Se粉、Sb I3粉、Gd粉为原料,用高压烧结法制备了Gd掺杂的n型Bi2Te2.7Se0.3热电材料,对制备的样品分别在573、603、633 K真空退火36 h。用粉末XRD和FE-SEM研究了样品的物相及显微形貌;在298-473K范围内测定了样品的热电性能。建立了Bi2Te3基材料的禁带宽度与压力和体积的近似关系式,利用此关系式较好解释了高压烧结样品在退火前后热电性能的变化特性。研究结果表明制备的样品在退火前后均为纳米结构。高压烧结和Gd掺杂使样品晶胞尺寸变大,禁带宽度减小。退火使高压烧结样品的电导率提高,塞贝克系数增大,热导率降低。样品于633 K退火36 h后具有较好的热电性能,在423 K时其ZT达到最大值为0.74。

With pure metal Bi, Te, Se, SbI3 and Gd powder as raw materials, n-type Bi2Te2.7Se0.3 doped with Gd were fabricated by a high pressure sintering method and then annealed for 36 h in a vacuum atmosphere at 573, 603 and 633 K for 36 h. The samples were characterized by X-ray diffraction and scanning electron microscope. The electric conductivity, Seebeck coefficient, and thermal conductivity were measured from 298 to 473 K. The formulas about the relationships among energy gap, volume and pressure have been established. The results show that the samples are consisted of nanocrystal grains before and after annealing. For the HPS sample with Gd doping, the cell size is bigger, and the band gap width is narrower. The electrical conductivity and Seebeck coefficient increase but thermal conductivity decrease after annealing. The maximum ZT value is 0.74 at 423 K, after the sample is annealed at 633 K for 36 h.