Study of crystallization processes in Bi-doped As2S3 chalcogenide glasses using linear isoconversion and isokinetic methods

A kinetic analysis of the crystallization processes in Bi-doped chalcogenide glasses was performed using the differential scanning calorimetry method. According to the results of X-ray diffraction measurements of the annealed samples, it was revealed that the crystallization process in the compound with 3 at% Bi takes part through the formation of Bi2S3 crystallization centers, while in the sample with 5 at% Bi, in addition to the appearance of Bi2S3, the centers of elemental As also occurred. These conclusions are in agreement with the results of thermogravimetric measurements. The crystallization activation energy (Ea), determined using Kissinger, Akahira and Sunose (KAS) method, was almost twice higher in the sample with the higher Bi content. This increase with Bi addition was associated with the significant modifications of the amorphous matrix structure. Using the methods of Gao-Wang and Šatava, it was found that the crystallization in the composition with 3 at% Bi, as well as the first crystallization process in the sample with 5 at% Bi takes place as a voluminous, three-dimensional process. The second crystallization process in the sample with 5 at% Bi is characterized with a two-dimensional, surface reaction mechanism, switching in the final stage into one-dimensional mechanism.