Synthesis, transformation and superconductivity of dual phase In–Sn alloy nanoparticles embedded in an Al matrix

We report the synthesis of nanoembedded biphasic alloy particles of In - Sn near eutectic alloy compositions embedded in an aluminium matrix by rapid solidification processing. Detailed transmission electron microscopy indicates that the two phases present at room temperature in as-synthesized samples are beta and gamma phases with tetragonal and hexagonal crystal structures, respectively. These co-exist with a small amount of single phase In or Sn particles with sizes less than 10 nm. Low temperature magnetization measurements indicate a superconducting transition temperature of 5 K, suggesting complete decomposition of the beta-phase at small sizes and at low temperature. The small particles show type II behavior with a critical field $Hc₁$ approximate to 44 G and two values for $Hc₂$ of 250 and 1000 G, respectively. These values are considerably lower than those observed in bulk In - Sn alloys.