Thermoelectric properties of n-type Bi2Se0.3Te2.7-based alloys with nanoflowers morphology

The n-type Bi2Se0.3Te2.7 nanopowders with nanoflowers morphology have been synthesized successfully by the hydrothermal method through using different amounts of ethylene diamine tetraacetic disodium salt (EDTA) as surfactant. As compared the Bi2Se0.3Te2.7 nanopowders with nanoplates morphology and Y0.2Bi1.8Se0.3Te2.7 nanopowders with nanoflowers morphology were also synthesized. Then, all the nanopowders were hot-pressed to pellets and the thermoelectric properties of the pellets were investigated. The results showed that the power factors of the samples made by the nanoflowers are all larger than that of the Bi2Se0.3Te2.7 bulk made by nanoplates due to their lower electrical resistivities which are caused by the larger grains in the corresponding bulk. In addition, the thermal conductivity of the Bi2Se0.3Te2.7 bulk made by nanoflowers is lower than that of the Bi2Se0.3Te2.7 bulk made by nanoplates due to the tiny grains embedded in the large grains in the bulk. As a result, in the measured temperature, the ZT values of the Bi2Se0.3Te2.7 bulk made by nanoflowers are all higher than that of the zone melt ingots. In the lower temperature, the ZT values of the Y0.2Bi1.8Se0.3Te2.7 sample are all high than 1.1 and reached 1.21 at 413 K which is relatively high value for n-type thermoelectric materials.