Experimental Study of the Sb-Sn-Zn Alloy System
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INTRODUCTION
TIN, antimony, and zinc are easily fusible metals used in many technical industries and areas of technology. Tin is mainly used as the major component of lowmelting solders.[1] Antimony and zinc are metals which can also be found in the solder alloy.[2] The commonly used Sn-Pb solder has been replaced by lead-free solders for environmental and health reasons. The most widely used lead-free solders for low-temperature soldering are Sn-Ag-Cu-based alloys (SAC solders).[3,4] Aside from the already established low-temperature lead-free solders there is still undergoing materials research of new alloys for brazing. Antimony and zinc are a common part of developed alloys for lead-free soldering.[5,6] An important source of information for the proposal of new alloys is the equilibrium phase diagram.[7] Details about coexistence and stability of phases including liquidus phase significantly streamline this material research. For this reason, this work pays special attention to experimental description of the Sb-Sn-Zn ternary system. Binary diagrams of Sb-Sn, Sn-Zn, and Sb-Zn[7] subsystems are known and they are described in great detail in Reference 8, 9. However, only little experimental information concerning Sb-Sn-Zn ternary alloy is known and experimental description of this system needs to be expanded. Some works dealing with thermodynamic phase coexistence in the ternary system were published in the period 1976 to 2011. The works dealt with the phase diagram of the Sb-Sn-Zn system,[10] structure of Sb2SnZn intermetallic phase[11] and metal activities in ternary liquid.[12] Some older sources[10,13,14] reported studies of the Sb-Sn-Zn system on account of
the use of the ternary intermetallic phase Sb2SnZn as a semiconductor. An important milestone of material research of alloys was the CALPHAD method developed in 1975[15] which was further developed (extended-generalized-adopted) for alloys.[16] The method is based on a thermodynamic description of the phases, which are described and parametrically stored in specialized databases.[7] Phase diagrams are possible to calculate using several different CALPHAD-based programs e.g., ThermoCalc[17] or Pandat.[18] Relevant thermodynamic database can be used to calculate equilibrium phase diagrams of binary subsystems, here Sb-Sn,[9] Sn-Zn,[7] and Sb-Zn.[8] The method also allows us to predict the ternary phase diagram of the Sb-Sn-Zn system, as the authors used before[19] and here for better understanding of the obtained experimental results. The CALPHAD method provides a prediction of stable phase diagram of the ternary system from binary subsystems. It fails, however, when the ternary system contains a ternary phase. This problem can also be observed in the Sb-Sn-Zn system where the stoichiometric ternary phase Sb2SnZn was experimentally observed.[10] Specification of the stability range of the ternary phase and positioning of the phase fields with mutual solubility of all three components was the motivation for the experimental study of Sb-Sn-Zn ternary system. C
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