Watching the Action: Powder Diffraction at non-ambient conditions

The Bi-Sn-Zn system has not been studied, till present, in all its extension; at least it was not done a complete optimization and assessment of the phase diagram. D. Malakhov et al. [1], as well as N. Moelans et al. [2], have only optimized and assessed the liquid phase of the ternary system due to the lack of data for the thermodynamic properties of terminal solid solutions as well as on their phase boundaries; only binary contributions were utilized, and the ternary terms were ignored. As this system seems to present some relevance for the development of lead free solder alloys, it was decided to study this system in more detail under the COST531 action from EU. Vertical sections for 60 wt% (Bi), 40 wt% (Bi), 5 wt% (Sn), 40 wt% (Sn), 60 wt% (Sn) and 80 wt% (Sn) were chosen for this study. Samples were melted from high purity elements in a resistance furnace and their compositions were confirmed by FRX. DTA/DSC measurements were performed in order to determine the temperatures for the phase transitions. Samples were observed by optical microscopy, as so as by SEM/EDS. Finally, XRD measurements at room and high temperatures were also performed in order to characterize the phases involved on some equilibria. Results were compared with those from the literature ([1] and [2]) indicating that the ternary terminal solid solutions should be assessed, at least (Bi) and (Sn). ____ [1] D. V. Malakhov, X. J. Liu, I. Ohnuma, K. Ishida, J. Phase Equil., 2000, 21 (6), 514-520. [2] N. Moelans et al. , J. Alloys and Comp. 360 (2003) 98.