电场对Bi-Sb-Te热电材料微观结构及其性能影响

分别采用热压、低电场强度和高电场强度3种工艺烧结制备Bi1.2Sb4.8Te9热电材料,测试、对比分析3组试样的微观结构和热电传输性能。结果表明,采用电场加热方式烧结可有效提高材料的致密度,且在大电场强度工艺下晶粒择优取向。电场可使材料内缺陷减少,载流子浓度下降,同时提高载流子迁移率,使材料综合电性能提高,晶粒择优取向有助于降低材料热导率,这些都有助于热电材料ZT值的提高。

The effect of electric field on the microstructure and thermoelectric performance of Bi-Sb-Te

Thermoelectric materials Bi1.2Sb4.8Te9 was sintered under three different conditions including no-current sintering(NCS),low-current density sintering(LCS) and high-current density sintering(HCS).The microstructure and thermoelectric performance of three groups’ samples were tested and compared.The results indicated that the applying of electric current in the sintering process can significantly improve the densification of samples,and the large electric field can make the grains oriented at the direction of the electric field.The electric field can eliminate crystal defects,and decrease the carrier concentration,and increase the carrier mobility.Thus the power factor was enhanced.The preferred orientation of grains can decrease the thermal conductivity.Therefore,a large electric field and high electric current in the sintering process may be the effective way to obtain thermoelectric materials with high value of the figure of merit ZT.