Thermoelectric properties of newly fabricated n-type 95%Bi 2Te 2–5%Bi 2Se 3 alloys by gas atomizing and extrusion process

Abstract

n-Type 95%Bi 2Te 3+5% Bi 2Se 3 compounds were newly fabricated by gas atomization process and extruded under different extrusion ratios (16:1 and 25:1) at 450 °C. The effect of extrusion ratio on the microstructure and thermoelectric properties was investigated by a combination of microscopy, X-RD and thermoelectric property testing. Grains of extruded bars are refined due to the dynamic recrystallization during extrusion and also slightly orientated along the extrusion direction. The grain size of the extruded bar at an extrusion ratio 16:1 was measured to be ≈2–5 μm, while it is ≈5–10 μm for the extrusion ratio of 28:1. The compressive strength of hot extruded bar under 25:1 is 160 MPa and with decreasing the extrusion ratio to 16:1, the value is 250 MPa. Extruded bar under ratio of 16:1 shows the higher value of figure of merit ( Z=2.50×10 −3 K −1) than that of 25:1 ( Z=2.07×10 −3 K −1).