Crystallization of amorphous Te-20 at% Sn alloy

Abstract

Amorphous Te-20 at% Sn alloy was obtained by rapid cooling from the liquid state. Phase transitions occurring during continuous heating of amorphous films were studied by differential thermal analysis, X-ray diffraction and transmission electron microscopy. It was found that the crystallization of the amorphous phase begins at 382 K and proceeds via nucleation and growth of metastable phases MS1 and MS2. The first of these phases was assigned the primitive cubic structure with lattice parameter a=3.2Å. The second phase, being a Te (Sn) solution, was assigned the hexagonal structure with lattice parameters a=4.45Å and c=5.85Å. During heating at 410 K the remaining amorphous phase decomposed into a mixture of Te crystals together with metastable phase MS3, which probably has the ZnS type structure with lattice parameter a=6.05Å. Within the temperature range 450 to 550 K the MS1 phase was transformed into SnTe, and the MS2 phase into Te. The metastable intermediate phase MS3 decomposed only near the solidus temperature, and the alloy attained its equilibrium structure.