| Summary: | 碩士 === 國立清華大學 === 化學工程學系 === 102 === Environmental-friendly materials and renewable energies are important topics among the critical sustainability issues. Solar energy is a major kind of renewable energies. Cu-In-Se (CIS) and its-based alloys are prevalent absorption layer materials in the solar cells and are essential to the cells' conversion efficiencies. Furthermore, there are many solder joints in solar cells. In terms of environmental friendliness, lead-free solders should be used. Sn-Ag-(In)-Zn alloys are promising lead-free solders. Understanding of the Cu-In-Se solar cell materials and Sn-Ag-(In)-Zn lead-free solders is important for the developments of environmental-friendly solar cells.
Phase diagrams are basic knowledge of materials. They are important tools for material developments, process selections and evaluations of product reliabilities. However, there are limited literatures of phase diagrams related to the Sn-Ag-Zn, Sn-Ag-In-Zn and Cu-In-Se systems. This study thus determines the liquidus projections of the Sn-Ag-Zn, Sn-Ag-In-Zn and Cu-In-Se systems. Liquidus projection is a projection diagram of the liquidus surfaces of space phase diagrams into a basal plane. It usually contains the information of primary solidification phases, the temperature descending directions of univariant lines and the temperatures of invariant reactions.
Sn-Ag-Zn, Sn-Ag-In-Zn and Cu-In-Se alloys were prepared from pure constituent elements. They were melted, mixed homogeneously together, and then quenched. The as-cast samples were metallographically examined. The primary solidification phases were determined based on the as-cast microstructures, compositional analysis and X-ray diffraction analysis. The temperatures of the invariant reactions were determined by using differential thermal analyzer. The liquidus projections of Sn-Ag-Zn, Sn-Ag-In-Zn and Cu-In-Se systems were constructed based on these experimental results and available phase diagrams of their binary constituent systems.
The liquidus projection of Sn-Ag-Zn and the isoplethal sections of the Sn-Ag-In-Zn liquidus projection are determined. There are eight primary solidification phases in the ternary Sn-Ag-Zn liquidus projection: ε2-AgZn3, γ-Ag5Zn8, β-AgZn, ζ-Ag4Sn, Ag, ε1-Ag3Sn, β-Sn and Zn phase. There are eight invariant reactions in this ternary system, including one class Ⅰ, six class Ⅱ and one class Ⅲ reactions. There are nine primary solidification phases at the 95.0, 90.0 and 85.0 wt.% Sn isoplethal sections of the quaternary Sn-Ag-In-Zn liquidus projection: ε1-Ag3Sn, ζ-Ag4Sn, β-AgZn, γ-Ag5Zn8, ε2-AgZn3, Zn, β-Sn, InSn4 and ζ phases.
There are 16 primary solidification phases in the ternary Cu-In-Se liquidus projection: β1-Cu2Se, Cu, β2-Cu4In, γ-Cu7In3, η-Cu2In, Cu11In9, In, In4Se3, InSe, In6Se7, In2Se3, Se, CuSe2, CuSe, α-CuInSe2 and δ-CuInSe2 phases. There are 19 ternary invariant reactions in this Cu-In-Se liquidus projection which are all involved with liquid phase. These invariant reactions include four class I, eight class Ⅱ and seven unknown types. In addition, there are two invariant reactions at the solid state are also been determined. Experimental difficulties of Se sublimation were encountered at the Se-rich corner, and it was the main reason for these undetermined types of the invariant reactions.
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