Evolution of thermoelectric performance for (Bi,Sb)2Te3 alloys from cutting waste powders to bulks with high figure of merit

• Bi2Te3 based wastes were directly selected as raw materials for TE alloys.
• Contaminants from cutting fluid and oxides could be effectively removed.
• Bulk Bi0.44Sb1.56Te3 with ZT of 1.16 was obtained from Bi2Te3 based wastes.
• Different from hydrometallurgy, the recycling method introduced here was green.
• Directly recycling Bi2Te3 wastes can lower raw material costs of manufacturers.

Bi2Te3 based cutting waste powders from cutting wafers were firstly selected as raw materials to prepare p-type Bi2Te3 based thermoelectric (TE) materials. Through washing, reducing, composition correction, smelting and resistance pressing sintering (RPS) process, p-type (Bi,Sb)2Te3 alloy bulks with different nominal stoichiometries were successfully obtained. The evolution of microstructure and TE performance for (Bi,Sb)2Te3 alloys were investigated in detail. All evidences confirmed that most of contaminants from line cutting process such as cutting fluid and oxides of Bi, Sb or Te could be removed by washing, reducing and smelting process used in this work. The carrier content and corresponding TE properties could be adjusted effectively by appropriate composition correction treatment. At lastly, a bulk with a nominal stoichiometry of Bi0.44Sb1.56Te3 was obtained and its' dimensionless figure of merit (ZT) was about 1.16 at 90 °C. The ZT values of Bi0.36Sb1.64Te3 and Bi0.4Sb1.6Te3 alloy bulks could also reach 0.98 and 1.08, respectively. Different from the conventional recycling technology such as hydrometallurgy extraction methods, the separation and extraction of beneficial elements such as Bi, Sb and Te did not need to be performed and the Bi2Te3 based bulks with high TE properties could be directly obtained from the cutting waste powders. In addition, the recycling technology introduced here was green and more suitable for practical industrial application. It can improve material utilization and lower raw material costs of manufacturers.

Three kinds of typical morphologies for the fractographs: typical lamellar structure, agglomerated submicron-sized granules and dispersed cubic particles from the initial cutting waste powders.Figure optionsDownload as PowerPoint slide