熱電材料Ge0.86Sb0.08Bi0.06Te在高溫Fm3 ̅m相的聲子色散關係

Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/89487

Title:	熱電材料Ge0.86Sb0.08Bi0.06Te在高溫Fm3 ̅m相的聲子色散關係
Authors:	郭于嘉;KUO, YU-JIA
Contributors:	物理學系
Keywords:	熱電材料;高溫;聲子色散;GeTe
Date:	2022-08-09
Issue Date:	2022-10-04 11:17:00 (UTC+8)
Publisher:	國立中央大學
Abstract:	GeTe屬於p型半導體的熱電材料，也屬於一種相變材料，現階段已知的GeTe晶體形式有三種，經研究顯示當兩種元素進行雙摻雜，如Sb及Bi，由於Bi的原子半徑較Sb大，且Bi由R3m 相轉變至Fm3 ̅m比Sb 快，討論樣品Ge0.86Sb0.08Bi0.06Te相轉變溫度，何時從α相(空間群R3m)相轉變至β相(空間群Fm3 ̅m)。並利用對中子繞射的原理獲得聲子彈性散射圖討論聲子的行為模式，彈性散射是對於粒子動能不守恆；非彈性散射則是動量守恆。當我們分析中子的散射路徑及中子和物質發生作用時動量與能量的變化，藉此來分析物質的微觀結構。使用SIKA 冷中子三軸散射儀作非彈性中子散射方式來測量Ge0.86Sb0.08Bi0.06Te中的激發能量，而色散關係主要描述波在傳遞過程中，其波長、頻率、波速等關係，針對聲子激發、聲子的色散關係與色散曲線、聲子生命期、群速度及傳播長度加以分析擬合以進行討論。由彈性散射的結果中發現在(110)625K及(200)525K後晶格常數上升速率有明顯改變，可能發生結構相轉變。而在聲子色散關係中，在(210)方向時，不同溫度下的聲子壽命則有相同上升的趨勢，反觀在(200)方向時，不同溫度下的聲子壽命則呈現下降的趨勢。而群速度及傳播長度則會與之相反。 ;GeTe belongs to the thermoelectric material of p-type semiconductor, and also belongs to a phase change material. There are three known crystal forms of GeTe at this stage. Studies have shown that when two elements are double-doped, such as Sb and Bi, the atomic radius of Bi is relatively small. Sb is large, and Bi transitions from R3m to Fm3 ̅m faster than Sb. This thesis discussed the phase transition temperature of sample Ge0.86Sb0.08Bi0.06Te to see when it transiforms from α phase to β phase, and by using the phonon elastic scattering diagram which came from the principle of neutron diffraction to obtain to discuss the behavior mode of phonon. Because elastic scattering is not conserved for particle kinetic energy, and inelastic scattering is momentum conservation. Therefore, we can analyze the microstructure of matter by observing the scattering paths of neutrons, and the changes of momentum and energy, which happened when neutrons interacted with matter.
Appears in Collections:	[Graduate Institute of Physics] Electronic Thesis & Dissertation

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