Kinetics of isothermal bulk crystallization of AsSe1,5Bix glasses (x = 0,01, 0,05)

Abstract

When As₂Se₃ glass is doped with tin, lead, or bismuth, isothermal bulk crystallization of the resulting glasses under optimal conditions is possible. The influence of bismuth concentration on the character and kinetic parameters of glasses crystallization has not been studied sufficiently. The purpose of this work is the comparative analysis of the kinetics of isothermal volumetric crystallization of As₂Se₃ and AsSe_1,5Bi_x glasses (x = 0,01 and 0,05). Glasses were synthesized by vacuum melting method from especially pure elemental substances with total mass of 7 g in the interval 700–900 С with the subsequent quenching of quartz ampoules with melts in air from 700 С. The kinetics of transformations during bulk isothermal crystallization of AsSe_1,5Bi_0,01 and AsSe_1,5Bi_0,05 glasses in the temperature range 210–260 С wаs studied by methods of density, microhardness, temperature dependence of electric conductivity, X-ray phase analysis of quenched samples. Analysis of the kinetics of bulk crystallization of the glasses was performed according to density measurements using the generalized Kolmogorov–Avrami equation. The addition of 2 at.% Bi to As2Se3 glass accelerated the crystallization of the main As₂Se₃ phase, reducing the latent period of the onset of As₂Se₃ phase separation by about 4 times and the kinetic period of half-transition by 13 times in comparison with the crystallization of pure As₂Se₃ glass. The effect of 0,4 and 2 at.% Bi additions on the isothermal crystallization of As₂Se₃ glass manifests itself mainly in decreasing the thermodynamic barrier and activation energy of bulk heterogeneous nucleation of lamellar As₂Se₃ phase crystals on primary Bi₂Se₃ phase nanocrystals. The reconstructive crystallization of the main phase of As₂Se₃ in AsSe_1.5Bi_0.05 glass is associated with a continuous change in the chemical composition of the residual glass phase and is characterized by an interval of decreasing values of the effective activation energy (142 → 114 ± 5 kJ/ mol).