热处理温度对冷烧结SnSe热电性能的影响研究

Impact of heat treatment temperature on the thermoelectric properties of cold-sintered SnSe

SnSe热电材料具有低热导率、低成本、环境友好等优势,成为目前热电领域的研究热点材料之一。本文利用水热法和冷烧结工艺制备了多晶SnSe块体,然后进行热处理,研究热处理温度对合成多晶SnSe热电性能的影响规律。XRD结果显示,各样品的主衍射峰与SnSe卡片相匹配。SEM结果表明,颗粒由块状变为片状结构且材料内部空隙随退火温度升高而降低。正电子湮灭测量结果表明,冷烧结的SnSe样品中可能存在各种空位型缺陷,如VSe、VSn、VSnSe和大空位团簇,这些空位型缺陷是有效的声子散射中心,导致晶格热导率降低,随着退火温度的升高,空隙减小与空位型缺陷逐渐恢复导致晶界势垒降低使电导率逐渐增大。电导率、功率因子和无量纲热电优值(ZT)的变化趋势几乎相同,都是随着退火温度的升高而增加。在测试温度为773 K时,500℃退火样品的电导率σ高达4.1×103 S/m,功率因子为3.71μW/(cm·K2);而热导率随着退火温度的提升减小了声子散射中心而略有升高。最后,计算500℃退火样品的ZT值为0.70,比未退火样品的ZT值高出35.7%。因此,表明了冷烧结工艺和热处理在SnSe材料研究中有巨大潜力,为制备出高性能热电材料奠定了理论依据。

SnSe thermoelectric materials are promising due to their low thermal conductivity,low cost,and environmental friendliness,making them a focus in thermoelectric research.This study explores the effects of heat treatment temperature on the thermoelectric properties of polycrystalline SnSe blocks prepared via hydrothermal synthesis and cold sintering.X-ray diffraction(XRD)analysis confirmed that the primary diffraction peaks of all samples corresponded with SnSe,while scanning electron microscopy(SEM)revealed a transformation from bulk to lamellar structures with reduced internal voids as annealing temperature increased.Positron annihilation spectroscopy indicated the presence of vacancy-type defects,such as VSe,VSn,VSnSe,and large vacancy clusters,which serve as phonon scattering centers,thereby reducing lattice thermal conductivity.As the annealing temperature rose,a decrease in voids and partial restoration of these defects lowered the potential barrier at grain boundaries,enhancing electrical conductivity.The electrical conductivity,power factor,and dimensionless thermoelectric figure of merit(ZT)increased consistently with higher annealing temperatures.At a test temperature of 773 K,the sample annealed at 500℃exhibited an electrical conductivity(σ)of 4.1×103 S/m and a power factor of 3.71μW/(cm·K2).Although thermal conductivity slightly increased with higher annealing temperatures due to reduced phonon scattering centers,the overall ZT value reached 0.7 for the 500℃annealed sample,a 35.7%improvement compared to the unannealed sample.These findings demonstrate that the combination of cold sintering and heat treatment is highly effective for enhancing the thermoelectric performance of SnSe,providing a theoretical basis for the development of high-performance thermoelectric materials.