Phase Equilibria in the Cu-Sn-Sb Ternary System X. J. Liu 1,2 · C. Wu 1 · M. J. Yang 1 · J. H. Zhu 1 · S. Y. Yang 1 · Z. Shi 1 · Y. Lu 1 · J. J. Han 1 · C. P. Wang 1 Submitted: 8 May 2018 / in revised form: 22 June 2018 / Published online: 15 October 2018 © ASM International 2018 Abstract The phase equilibria in the Cu-Sn-Sb ternary system were investigated by means of electron-probe microanalysis and x-ray diffraction. Firstly, ternary solu- bilities of η-Cu 6 Sn 5 , δ-Cu 41 Sn 11 , Cu 11 Sb 3 , ε-Cu 3 Sb and η- Cu 2 Sb, were less than 7 at.% Sb or Sn at 400 °C. Besides, an re-stabilized ternary solubility, Cu 6 (Sn,Sb) 5 , was detected with a homogeneity range of Cu: 52.9-53.3 at.%, Sn: 28.4-30.9 at.%, and Sb: 15.8-18.7 at.%. Its origin was traced back to high-temperature stabilization of the binary η-Cu 6 Sn 5 phase. Thirdly, the metastable phase, Cu 11 Sb 3 , was observed at 400 °C in the Cu-Sn-Sb ternary system; On raising the temperature to 500 °C, the ε-Cu 3 Sn phase still retained a large solubility for Sb, at  16 at.%, while the ε-Cu 3 Sb was replaced by β-Cu 3 Sb with a dual-cornered large homogeneity range. Similarly, a ternary homogeneity range of Cu: 83.8-84.9 at.%, Sn: 2.6-6.2 at.%, and Sb: 9-12.5 at.%, was found and deduced to be the high tem- perature stabilization phase of γ-Cu 11 (Sb,Sn) 2 at 500 °C. Keywords Cu-Sn-Sb ternary system · phase equilibria · ternary solubility 1 Introduction and Literature Review Tin-lead (Sn-Pb) solders were widely used in the elec- tronics industry during past decades because of its good joining performance and low price. However, Pb and its compounds can bring great harm to the environment and jeopardize the safety of human life. Currently, the most used Pb-free solder is Sn-Ag-Cu [1,2] based alloy, which has higher production costs. Therefore, many efforts are devoted to the development of a new Pb-free solder with lower cost. [3,4] Many investigations had reported that replacement of the element Pb with Sb was a good alter- native. [5,6] However, the thermodynamic information per- taining to Sb are very limited. Another issue is that copper, which is widely used in electronic products, reacts with the elements of Sn and Sb during the soldering process. The resulting intermetallic compounds, e.g. η-Cu 6 Sn 5 , may affect significantly the reliability of the solder. Therefore, the object of the present investigation is to study experi- mentally the phase equilibria of the Cu-Sn-Sb ternary system over the whole composition range. Three binary subsystems Sn-Sb, [7] Cu-Sn [8] and Cu-Sb [9] constitute the Cu-Sn-Sb ternary system. The crystal struc- tures of the related phases are shown in Table 1. There was still a lot of controversy in the Cu-Sn-Sb ternary and its sub-binary systems as following discussed: Early studies believed that two intermetallic compounds, β-SnSb and Sn 3 Sb 2, were contained. [10] The β-SnSb phase has an extended homogeneity range from 43 to 65.2 Sn (at.%). However, recent research results showed that the Sn 3 Sb 2 was not found and the Sb 3 Sn 4 takes the place of it. [7,11] The Cu-Sb and Cu-Sn binary systems are more complex and have been studied by many researchers. [12-16] Murakami and Shibata [17] first measured the boundaries of the β phase in the Cu-Sb binary phase diagram and confirmed that the & C. P. Wang wangcp@xmu.edu.cn 1 College of Materials and Fujian Provincial Key Laboratory of Materials Genome, Xiamen University, Xiamen 361005, People’s Republic of China 2 Department of Materials Science and Engineering, Harbin Institute of Technology, Shenzhen 518055, Guangdong, People’s Republic of China 123 J. Phase Equilib. Diffus. (2018) 39:820–831 https://doi.org/10.1007/s11669-018-0681-9