Ageing-induced structural evolution of mechanically alloyed Ga40Se60

After four years of ageing at room temperature, a nanocrystalline Ga(40)Se(60) alloy produced by mechanical alloying was re-investigated using x-ray diffraction and differential scanning calorimetry techniques. The results show that this sample, mainly a monoclinic Ga(2)Se(3) phase, evolved to a multi-phase crystalline alloy, mainly a trigonal Se one, containing also minority crystalline phases. The monoclinic Ga(2)Se(3) phase remains visible after ageing and the nucleation of the Se-O and Se phases is attributed to migration of Se atoms located at interfacial components of the as-milled sample. Similar ageing effects were also observed for a portion of Ga(40)Se(60) alloy annealed four years ago.