Microstructure development and thermoelectric properties of Bi2Te3 ceramics fabricated by PIES method

Thermoelectric ceramics of p- and n-type bismuth telluride were fabricated by the so-called PIES (pulverized and intermixed elements sintering) method, for which various sintering techniques, such as HIPping, hot-pressing, and plasma sintering, were employed. Microstructure of a compact developed via a dissolution-precipitation mechanism in all cases, and the final products showed the figure of merit as large as 2.0-2.6×10^-3 K^-1 when the average grain size was 2-10 μm, because their thermal conductivity became the lowest possibly due to enhanced phonon scattering at grain boundaries. Isotropic microstructure with no apparent grain orientation gave rise to isotropic thermoelectric properties and substantial compressive strength of the order of several MPa, firmly suggesting that these ceramics can be applied to industrial uses