Effect of copper introduction into As2Se3 glass matrix on crystallization processes

• Crystallizations in glasses of the Cux(As2Se3)100 − x system were analyzed.
• Crystallization of three structural units occurred: As2Se3, CuAsSe2 and Cu2Se.
• The crystallization of As2Se3 has value of the Avrami index n = 4.
• The crystallization of Cu2Se and CuAsSe2 has the value of the Avrami index n = 3.
• The highest value of activation energy of crystal growth corresponds to Cu2S unit.

Crystallization processes in glasses of the Cux(As2Se3)100 − x system for x = 0, 1, 5, 10 and 15 at.% were analyzed by non-isothermal differential scanning calorimetry at different heating rates. Based on the obtained thermograms, the mechanism of incorporation of copper into amorphous As–Se matrix and changes in the structure of the investigated system were analyzed. It was shown that the crystallization process essentially depends on the composition. Depending on the glass composition and the applied heating rate, crystallization of three structural units occurred: As2Se3, CuAsSe2 and Cu2Se. Activation energies of the crystal growth of these structural units were determined. The parameters n and m, numerical factors which depend on the morphology of nucleation and growth, were determined. The analysis of the mechanism of crystallization has shown that the crystallization of As2Se3 is characterized by the value of the Avrami index n = 4, which indicates that volume nucleation and three-dimensional growth with variable number of centers of nucleation is involved. Analogous, analysis of the crystallization of structural units Cu2Se and CuAsSe2 has shown that the Avrami index has a value of n = 3 (m = 3) that corresponds to the volume nucleation and three-dimensional growth, but the number of centers of nucleation does not change.