Microstructural and thermal evaluation of the formation of tin–tellurium (Sn–Te) alloy by ball milling process

A mechanically induced phase transition in tin‑tellurium (Sn–Te) system and its dependence on the milling time of the masses of metastable Sn–Te phase(s) produced during ball milling have been investigated. The synthesis approach involves top-down ball milling of elemental Sn and Te powders in an argon environment with a milling time of 1 to 5 h at a low ball milling speed of 300 RPM. The Sn–Te solid solution forms as particles, resulting in large masses due to the ball milling operation. Ball milling of initial micron-sized powders of Sn and Te resulted in a homogenized nano-sized powder mixture. This mechanical mixture of Sn and Te powders exhibiting intermediate phases with a crystal structure similar to that of elemental Sn and Te were detected in the ball-milled mixtures at various milling times, which resulted in a stable phase that ultimately transformed into a Sn–Te solid solution. Morphological and structural modifications at different stages of ball milling were investigated through X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, differential scanning calorimetry, dynamic light scattering, density measurement, and surface analysis. Subsequently, dense pellets were fabricated by spark plasma sintering from synthesized Sn–Te solid-solution powders produced by ball milling for 5 h. The sintered samples showed excellent structural integrity with densities of up to 6.35 g/cm³. It is to be noted that the formation of large quantities of uniform Sn–Te powder alloy produced by ball milling is reported for the first time in this study. These findings could be extended in the future to prepare bulk quantities of many solid solutions of the elements of the same periodic group.