High performance production of Bi₂Te₃ based thermoelectric materials on the route of the bulk mechanical alloying method

In the commercial fabrication of thermoelectric materials, melting, ingot-making, pulverizing and sintering are fundamental steps for production. In the present new-production method on the route of bulk mechanical alloying, the elemental constituent granules or agglomerates with any selected composition can be used for direct solid-state synthesis into single or dual phase thermoelectric materials. Bi-Te-Sb system is adopted as the targeting thermoelectric materials to investigate the effect of fine-grained structure on the figure of merit. In addition, temperature and pressure conditions in hot pressing are widely varied to describe the effect of process parameters on the thermoelectric properties. As a rough sketch of high performance in this processing, 3.6 ks for fabrication of green compact with the relative density of 85% T.D., 3.6 ks for hot pressing to have fine grain size in 1 approximately 2 μm for high density of 99% T.D. or more, and Z = 3.15×10^-3/K in p-type Bi-Te system for the highest figure of merit.