制备工艺对n型Bi_2Te_3基材料热电性能和抗压强度的影响

以商用区熔(ZM)n型Bi2Te3基材料为原料,采用简单研磨结合放电等离子烧结技术(ZM+SPS)和熔体旋甩(MS)结合放电等离子烧结技术(MS+SPS)制备了n型Bi2Te3基块体热电材料.对三种不同工艺制备出样品的微结构、热电性能和力学性能进行了研究.FESEM微结构表征结果表明:区熔样品的晶粒粗大,有较强的取向性;经SPS烧结后,晶粒细化,取向性大为降低;而区熔样品经MS+SPS后,晶粒得到进一步细化,且没有明显的取向性.对三组样品进行的热电性能和抗压强度测试,结果表明:区熔原料最大ZT值为0.72(430K),抗压强度仅为40MPa;经SPS后,样品的最大ZT值为0.68(440K),抗压强度为110MPa,相比区熔样品提高了175%;MS+SPS样品的最大ZT值为0.96(320K),其室温ZT值相比区熔样品提高了64%,抗压强度相比区熔样品提高了400%,达到200MPa.

Effects of Preparation Techniques on the Thermoelectric Properties and Pressive Strengths of n-type Bi2Te3 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.