纳米BaTiO3复合Cu1.8S块体的热电性能和力学性能研究

Thermoelectric and Mechanical Properties of Nano BaTiO3 Composited Cu1.8S Bulks

摘要:

Cu_1.8S作为一种P型半导体热电材料,具有环境友好、原料丰富、价格低廉等优点而受到广泛关注。本研究采用机械合金化(Mechanical Alloying, MA)结合放电等离子烧结(Spark Plasma Sintering, SPS)工艺制备了一系列Cu_1.8S-x wt%BaTiO₃ (x =0,0.075,0.1,0.15,0.2)块体材料,研究了复合纳米BaTiO₃对Cu_1.8S的相结构、微观形貌、热电性能及力学性能的影响。结果表明,纳米BaTiO₃的加入不影响Cu_1.8S的相结构、晶胞参数和载流子浓度；纳米BaTiO₃均匀分布在Cu_1.8S基体的晶界处产生钉扎效应进而细化晶粒并产生气孔。Cu_1.8S-0.2 wt%BaTiO₃样品在773 K时获得最低的热导率2.2 Wm^_-1K^_-1,所有样品的ZT值基本保持不变约0.39 (773 K)。同时Cu_1.8S-x wt%BaTiO₃块体样品的维氏硬度由82 (x = 0)增加到87 (x = 0.2)。本研究表明在Cu_1.8S中复合纳米BaTiO₃可以在不影响材料热电性能的前提下有效提升块体样品的力学性能,为后续Cu-S体系热电性能和力学性能的协同提升提供了思路,有利于制备高机械性能且稳定耐用的Cu-S体系的热电器件。

Abstract:

Digenite (Cu_1.8S) as a potential p-type thermoelectric (TE) material has attracted extensive attention due to its environmental benign, abundant resources and low cost of component elements. In this study, the TE properties of Cu_1.8S-x wt%BaTiO₃ bulk samples prepared by mechanical alloying (MA) combined with spark plasma sintering (SPS) were investigated. Adding BaTiO₃ would refine grains, thereby increasing the phonons scattering and reducing the thermal conductivity k. The k for Cu_1.8S-0.2 wt%BaTiO₃ is 2.2 W m^_-1 K^_-1 which is 18% lower than that for pristine Cu_1.8S (2.69 W m^_-1 K^_-1). The refined grains also enhance the carriers scattering, and reduce the carrier mobility to reduce the power factor (PF). Combine with the decreased PF and k, the calculated ZT values are barely unchanged for adding BaTiO₃ in Cu_1.8S. The Vickers-hardness for BaTiO₃-adding samples are improved due to the refined grains and the pinning effect of BaTiO₃ on grain boundary. This study shows that the mechanical properties of Cu_1.8S bulk samples can be effectively improved by compositing nano BaTiO₃ with little affecting TE properties, which provides ideas for preparing high mechanical properties and durable TE devices of Cu-S system.