Thermal analysis and Raman scattering study on crystallization and structure of Ag x(As 0.4Se 0.6) 100− x glasses

Abstract

Differential scanning calorimetry (DSC), X-ray diffraction (XRD), and Raman scattering measurements for Ag x (As 0.4Se 0.6) 100− x glasses with x=0–35 at.% were carried out to investigate the crystallization kinetics and the local structure. The DSC curves were obtained at various heating rates for different Ag contents and two or three exothermic peaks for the crystallization were found depending on the Ag content. The XRD phase analysis has shown that the cubic AgAsSe 2 is formed in the first crystallization process and it is then transformed into the tetragonal AgAsSe 2 phase. Small Ag 3AsSe 3, Ag 2Se, and Ag 7AsSe 6 phases were additionally found in the crystallization of the samples with x=30 and 35 at.%. In order to determine the dimension of crystal growth of sample particles and activation energy, the DSC data were analyzed using Matusita’s equation. It was found that the surface and bulk crystallization take place depending on the Ag content and peak crystallization temperatures. The Raman spectra of the glasses with high Ag content ( x=15–35 at.%) are different from those for low Ag content. The latter spectrum is attributed to the symmetrical stretching mode of a pyramidal AsSe 3 molecule consisting of the As 2Se 3 glass and the former spectrum is attributed to the molecular vibration of a threefold As 3Se 6 ring consisting of the AgAsSe 2 glass.