PbTe、Pb0.78Sn0.22Te與Ge0.5Pb0.25Sn0.25Te的熱電物性研究
Abstract
本實驗利用晶體熔融淬火和火花電漿燒結法(SPS)製備PbTe的熱電材料，PbTe的熱電優質係數(ZT)約0.25。我們希望藉Sn、Ge取代部分Pb合成新的熱電材料Pb0.78Sn0.22Te及Ge0.5Pb0.25Sn0.25Te，來提高其熱電優質係數。以X光繞射儀(XRD)和X光螢光分析儀(XRF)來鑑定晶體結構及材料中各元素成份比例，以熱電分析儀器測量其熱電性質，如席貝克係數、電阻率、熱傳導係數與溫度(300-600 K)的關係。其中的熱傳導係數由熱擴散係數、比熱、密度三者相乘得來。實驗結果顯示Sn、Ge取代部分Pb確能提高其熱電優質係數達~0.35。
The figure of merit (ZT) of thermoelectric material PbTe is about 0.25. In order to study the doping effect on the ZT, the alloys of Pb0.78Sn0.22Te and Ge0.5Pb0.25Sn0.25Te were formed from PbTe through partially substituting Pb by Sn and Ge. All samples were prepared by melting and followed by water quench. These samples were powdered by grinding and then pressed by Spark Plasma Sintering (SPS) to further reduce their thermal conductivities. X-ray diffraction (XRD) and X-ray fluorescence (XRF) were employed to examine their crystal structures and composition ratios. The temperature dependence of the Seebeck coefficient, resistivity and thermal conductivity (obtained by the product of specific heat, mass density and diffusivity) of Pb0.78Sn0.22Te and Ge0.5Pb0.25Sn0.25Te showed that the ZT was slightly enhanced from 0.25 to 0.35 by the Pb substitution and processes of Spark Plasma Sintering.
The figure of merit (ZT) of thermoelectric material PbTe is about 0.25. In order to study the doping effect on the ZT, the alloys of Pb0.78Sn0.22Te and Ge0.5Pb0.25Sn0.25Te were formed from PbTe through partially substituting Pb by Sn and Ge. All samples were prepared by melting and followed by water quench. These samples were powdered by grinding and then pressed by Spark Plasma Sintering (SPS) to further reduce their thermal conductivities. X-ray diffraction (XRD) and X-ray fluorescence (XRF) were employed to examine their crystal structures and composition ratios. The temperature dependence of the Seebeck coefficient, resistivity and thermal conductivity (obtained by the product of specific heat, mass density and diffusivity) of Pb0.78Sn0.22Te and Ge0.5Pb0.25Sn0.25Te showed that the ZT was slightly enhanced from 0.25 to 0.35 by the Pb substitution and processes of Spark Plasma Sintering.
Description
Keywords
熱電優質係數, figure of merit (ZT)