Effects of Preparation Techniques on the Thermoelectric Properties and Pressive Strengths of n-type Bi_2Te_3 Based Materials

The zone-melted n-type Bi2Te3 ingots were chosen as the starting material to prepare the bulk samples by two different synthesis routes including hand grinding combined with spark plasma sintering process(ZM+SPS) and melt spinning(MS) technique combined with a subsequent spark plasma sintering process(MS+SPS).The microstructures,thermoelectric properties and mechanical properties of three samples prepared by different techniques were studied.The ZM samples show rough grain size and strong grain orientations.After hand grinded and SPS process,the crystalline grains are refined and grain orientations are remarkably decreased.While the MS+SPS samples with fine grains have no distinct grain orientations.The results of thermoelectric properties and pressive strength measurement show that the maximum figure of merit ZT value reaches 0.72 at 430 K for ZM starting materials and the pressive strength is only about 40MPa.The maximum figure of merit ZT value decreases to 0.68 at 440 K for the ZM+SPS samples but the pressive strength are increased to 110MPa,which is about 175% improvement compared with ZM samples.The maximum figure of merit ZT value and pressive strength are 0.96 at 320 K and 200MPa respectively for the MS+SPS samples,the room temperature ZT and pressive strength are about 64% and 400% improvement compared with ZM samples.