Cr 도핑이 다결정 SnSe의 열전 특성에 미치는 영향

Thermoelectric;doping;SnSe;Cr;figure of merit;mechanical alloying;spark plasma sintering;620.1

공과대학 재료공학부 ;

University:서울대학교 대학원

关键词: Thermoelectric;    doping;    SnSe;    Cr;    figure of merit;    mechanical alloying;    spark plasma sintering;    620.1;   

Others  :  http://s-space.snu.ac.kr/bitstream/10371/141475/1/000000151445.pdf

美国|英语

来源: Seoul National University Open Repository

【 摘 要 】

Single crystal SnSe has been a promising thermoelectric (TE) material since it’s high ZT value of ~2.6 at 923K. However, due to the weak mechanical strength and complicated processing to make the single crystal SnSe, studies to improve TE properties of polycrystalline SnSe have been carried out. Polycrystalline SnSe has significantly low electrical conductivity compared to the single crystal SnSe due to the low carrier concentration. Therefore, enhancement of the carrier concentration is needed for polycrystalline SnSe to be used effectively in practical applications. One of the effective methods to control the carrier concentration is doping. TE properties of polycrystalline SnSe with doping were reported. The highest ZT values(ZT=0.96) of Zn7) doped polycrystalline SnSe was achieved. However, to commercialize the thermoelectric materials, the efficiency should be higher than 10%(ZT>1). Therefore, a new doping elements which can further improve the TE performance is needed. Chromium was chosen as the new doping element because of cheap price, high abundance and suitable element based on hume-rothery rule. In this study, the effect of Cr doping on the thermoelectric properties of polycrystalline SnSe was investigated. Sn1-xCrxSe (x=0, 0.01, 0.03, 0.05 mol%) powders were prepared by mechanical alloying. And then, Cr doped SnSe bulk samples were fabricated by spark plasma sintering. Phase and microstructure of the samples were analyzed by XRD and FE-SEM, respectively. From the XRD and EDS mapping, the solubility limit of Cr doping in polycrystalline SnSe was 1mol%. With the increasing amount of Cr, the electrical conductivity enhanced due to the increase of hole concentration. While the seebeck coefficient decreased with the increase of hole concentration. The presence of second phase(Cr5Se8) from the 1mol% of Cr doping, decreased the hole mobility. Resulting in a decrease in electrical conductivity and increase in seebeck coefficient. With the decrease of hole mobility, the effective mass has increased from the inverse proportional relationship of these two parameters. Thus, increase of effective mass has enhanced seebeck coefficient. The substitution of Cr in Sn site decreased the thermal conductivity by alloy scattering. The presence of second phase(Cr5Se8) in matrix decreased the thermal conductivity by scattering phonons. Consequently, the pure effect of Cr doping in polycrystalline SnSe was obtained with 0.5mol%. ZT value of 0.88 was achieved at 773K for 0.5mol% of Cr doped polycrystalline SnSe with the increase of electrical conductivity and decrease in thermal conductivity.