Thermal crystallization behavior of As-Te glasses

Abstract

Thermal crystallization behavior of As_xTe_100-x (25≤ x≤ 60) glasses is studied by differential scanning calorimetry. As_xTe_100-x glasses with x<40 are found to exhibit one glass transition and one crystallization reaction, during heating. On the other hand, glasses with 40≤ x≤ 50 show one glass transition and two crystallization reactions. Unlike other binary telluride glasses, the first crystallization reaction in As_xTe_100-x glasses does not correspond to the precipitation of hexagonal Te. It corresponds to the formation of a metastable intermediate crystalline phase, which transforms into the equilibrium As₂Te₃ phase at the second crystallization reaction. As a consequence of this difference in the crystallization behavior, As_xTe_100-x glasses with 40≤ x≤ 50 do not show the phenomenon of double glass transition. Further, the two crystallization reactions of these glasses are found to merge progressively, with the increase in arsenic content. As a result, As_xTe_100-x glasses with 50<x≤ 60 show only one crystallization reaction. An explanation for this interesting crystallization behavior of As_xTe_100-x glasses is provided with the help of x-ray diffraction, electron microscopy, and thermogravimetry studies.