Origin of contamination and role of mechanochemistry during mechanical alloying: the case of Ag–Te alloys

We show that enhanced reaction of the vial materials with the milled samples can take place during the non-equilibrium processing route of mechanical alloying leading to the introduction of significant contamination. The increase in reactivity could be attributed to the grain size reduction to nanoscale during the milling process. Our attempt at mechanical alloying of elemental silver and tellurium powder using agate and zirconia grinding media to obtain contamination-free silver telluride (Ag2Te) phase with fine grain size has lead to the evolution of silver silicate (Ag2SiO3) and zirconium telluride (ZrTe2) phases, respectively which contaminate the Ag2Te phase. On the other hand, no contamination could be observed when tungsten carbide (WC) vial and balls are used. Attempts have been made to rationalize the observations in terms of changes in thermodynamics and kinetics at small length scale.