熱電元件能將廢熱回收，提高能源使用效率。Pb-Se-Sn-Te四元系統，包含許多具有熱電應用潛力的材料，具有熱電應用的重要性。本研究探討Pb-Se-Sn-Te四元系統的相圖，提供基礎材料知識，作為Pb-Se-Sn-Te四元系統相關材料開發的基礎。Pb-Se-Sn-Te的六個組成二元系統為Pb-Se、Pb-Sn、Pb-Te、Se-Sn、Se-Te與Sn-Te，四個組成三元系統為Pb-Se-Sn、Pb-Se-Te、Pb-Sn-Te與Se-Sn-Te。此六個二元系統的相圖，在文獻中已有相當多的探討，也皆有Calphad型式熱力學模型描述。Pb-Sn-Te與Se-Sn-Te二個組成三元系統，文獻中也有相關相圖的探討與Calphad型式的熱力學敘述。針對六個組成二元系統與Pb-Sn-Te與Se-Sn-Te二個組成三元系統的相圖，本研究將直接引用文獻的結果，不再重複進行探討。針對Pb-Se-Te 與 Pb-Se-Sn 二個欠缺相平衡資料的三元系統，本研究進行相圖實驗的測定與探討。在350oC與500oC的Pb-Se-Sn-Te四元系統中，穩定的二元相包含PbSe、Se2Sn、SeSn、PbTe 與 SnTe。PbSe與PbTe及PbTe與SnTe分別生成Pb(Se,Te)及(Pb,Sn)Te連續固溶體。其他二元相並未含有連續固溶體，但彼此間有較高的溶解度。Pb-Se-Te與Pb-Se-Sn二個三元系統在350oC與500oC皆沒有穩定的三元相。依據相圖實驗的結果、以及現有組成二元系統的相圖，本研究推定了Pb-Se-Te與Pb-Se-Sn二個三元系統在350oC與500oC的等溫橫截面圖。Pb-Se-Sn 三元系統在350oC與500oC，含有liquid(Se)+γ-SeSn+α-PbSe、liquid(Se)+γ-SeSn +Se2Sn 與 γ-SeSn+α- PbSe+liquid (Pb-Sn)等三個縛三角(tie-triangles)。而在 Pb-Se-Te三元系統，350oC 中含有PbSe+liquid+(Se-Te)一個縛三角；500oC未有縛三角。針對Pb-Se-Sn-Te四元系統，本研究探討了PbSe、PbTe、SeSn與SnTe在500oC的單相固溶體區間。本研究也使用Calphad的方法，以二元系統的熱力學參數，在未引入三元交互作用的參數下，直接進行二元與三元系統的相圖計算，並與實驗結果進行比較。

Thermoelectric devices can enhance energy usage efficiency by recovering waste heat and converting it into electric energy. Pb-Se-Sn-Te is a quaternary material system of high thermoelectric application interests. This study determines the phase diagrams of Pb-Se-Sn-Te quaternary system to provide fundamental information for the development of Pb-Se-Sn-Te-related thermoelectric materials. Pb-Se-Sn-Te quaternary system has six constituent binary systems, Pb-Se, Pb-Sn, Pb-Te, Se-Sn, Se-Te and Sn-Te and four constituent ternary systems, Pb-Se-Sn, Pb-Se-Te, Pb-Sn-Te and Se-Sn-Te. There are phase equilibria experimental measurements and Calphad-type thermodynamic descriptions of all the six constituent binary systems and the two constituent ternary systems, Pb-Sn-Te and Se-Sn-Te. Regarding these six binary systems and the two ternary systems, this study will assess and use the phase diagrams results in the literatures without repeating experimental measurements. Experimental measurements are carried out to determine the phase diagrams of Pb-Se-Te and Pb-Se-Sn systems which are lacking in the literatures. The stable binary compounds in the Pb-Se-Sn-Te quaternary system at 350oC and 500 oC are PbSe, Se2Sn, SeSn, PbTe and SnTe. Pb(Se,Te) and (Pb,Sn)Te are continuous solid solutions. The other binary phases do not form continuous solid solutions, but most of them have significant solubilities. There are no ternary compounds in the Pb-Se-Sn and Pb-Se-Te systems. Based on the experimental phase diagrams measurements and the phase diagrams of constituent binary systems, the Pb-Se-Sn and Pb-Sn-Te isothermal sections at 350oC and 500 oC are determined. The Pb-Se-Sn ternary system at 350oC and 500oC have the following tie-triangles, liquid(Se)+γ-SeSn+α-PbSe, liquid(Se)+γ-SeSn +Se2Sn, and γ-SeSn+α-PbSe+liquid(Pb-Sn). In the Pb-Se-Te ternary system at 350 oC, the tie-triangle is Pb(Se-Te) +liquid+(Se-Te) and there is no tie-triagle at 500 oC. The compositionally wide solid solution region in the Pb-Se-Sn-Te quaternary system composed of PbSe-PbTe-SeSn-SnTe is experimentally determined in this study. Besides experimental measurements, this study also calculates the phase diagrams of the binary and ternary systems using just the thermodynamic descriptions of the binary systems without introducing ternary interaction parameters.

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