Kinetics of crystal growth of germanium disulfide in Ge0.38S0.62 chalcogenide glass

• Published in: Journal of non-crystalline solids 2005-03, Vol.351 (6-7), p.557-567
• Main Authors: Shánělová, Jana, Málek, Jiří, Alcalá, Maria D., Criado, José M.
• Format: Article
• Language: English
• Subjects: Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Growth from solid phases (including multiphase diffusion and recrystallization); Materials science; Methods of crystal growth; physics of crystal growth; Physics
• ISSN: 0022-3093; 1873-4812
• DOI: 10.1016/j.jnoncrysol.2005.01.042

The crystal growth kinetics of GeS2 in Ge0.38S0.62 glass has been studied by Differential Scanning Calorimetry (DSC) and microsopy. The linear crystal growth kinetics of both high temperature α-GeS2 and low temperature β-GeS2 polymorphs has been observed over a relatively broad range of temperatures, i.e. 4208×105 Pas. It seems that 2D nucleated growth is the most probable mechanism of crystallization for high temperature α-GeS2 under these conditions. However, there are significant deviations for this model for the crystallization of low-temperature β-GeS2. This might indicate some changes in crystal-melt interfacial energy or break down of Stokes–Einstein relation in that particular case. At temperatures below 500°C the temperature range of directly observed crystal growth overlaps with isothermal DSC measurements. In this case overall crystallization kinetics can be described by the Johnson–Mehl–Avrami (JMA) nucleation-growth model for kinetic exponent n≅4. The value of activation energy of nucleation estimated from these experiments EN=434 kJmol−1 is comparable with the activation energy of viscous flow in supercooled Ge0.38S0.62 melt (Eη=478 kJmol−1). A more complex eutectic crystallization involving both GeS2 and GeS phases has been observed at higher temperatures. This process is probably associated with secondary nucleation and cannot be described by a simple JMA model.