Crystal Growth Kinetics in Se–Te Bulk Glasses

Abstract

The isothermal crystal growth in Se 100−x Te x bulk glasses (x = 10, 20, and 30) was studied directly using infrared microscopy. The crystals grew spherulitically and linearly in the course of time, which is typical for crystal growth controlled by liquid-crystal interface kinetics. An operative growth model was found using a combination of growth and viscosity data, and using two different approaches for calculations of the Gibbs free energy change between the undercooled melt and crystalline phase. The study shows that the exact knowledge of the Gibbs free energy change calculated from both, heat capacities, and the simple approximation proposed by Turnbull, can provide comparable results regarding determination of an operative crystal growth model. A detailed discussion about the relationship between the kinetic coefficient of crystal growth rate and viscosity (u kin ∝ η −ξ ) is presented. Moreover, the activation energies of crystal growth were found to be higher than the activation energies of the overall crystallization process obtained by differential scanning calorimetry. The relation between these two quantities is considered under the experimental conditions. ■ INTRODUCTIONChalcogenide glasses and thin films are very interesting materials that exhibit unique physical properties. Because of their diverse active properties, chalcogenide materials can be used in various optical and optoelectronical devices or in various electronic thresholds and switches. 1−3 Interesting applications of chalcogenide materials also are found in modern high-tech memory devices. 4−6 Thermal stability and crystallization play a key role in processing and usage of the materials. In particular, the crystallization process needs to be considered from two points of viewin order to obtain an ideal glass the crystallization has to be prevented, and, on the other hand, the controlled amorphous-to-crystalline transformation is a fundamental process of considered technology (modern phase change materials, PCM). Thus, knowledge and understanding of crystal growth kinetics and nucleation in such materials are essential for their future applications. The crystallization studies 7−11 focus on evaluation of mechanism of crystal growth and nucleation, and on prediction of crystallization behavior in a wide temperature range. Such a description can be useful for tailoring and optimization of new high-tech materials as they provide a possibility to predict the crystallization behavior in similar materials by revealing the basic mechanisms and properties of the material.Selenium-based materials have been commercially applied in photoreceptors, photovoltaic materials, etc. 12 The properties of pure selenium can be significantly improved by alloying with other elements such as tellurium, germanium, antimony, arsenic, etc. Se−Te glasses and thin films are very attractive materials that exhibit an intermediate behavior between pure selenium and tellurium. The Se−Te mixtures exhibit numerous advantages in comparison with pure Se, for example, great...

Rotating lattice single crystal architecture on the surface of glass

“…This is a completely unexpected result from the classical theory of crystallization by nucleation and growth, and spherulitic growth mode has been suggested to explain these observations. Such spherulitic crystal growth has been observed in a wide range of substances that crystallize from high viscosity melt or solutions1415161718192021222324. However, its mechanism, in particular the source of non-crystallographic branching in spherulites remains unclear7.…”

“…However, its mechanism, in particular the source of non-crystallographic branching in spherulites remains unclear7. So the knowledge of how lattice rotation is introduced is important for understanding the formation of spherulites145671415161718192021222324 as well as biominerals910111213. The ability to control this rotation will help fabricate ‘bio-inspired’ materials that mimic the structure of biominerals and hence their superior properties25.…”

Structure of Se–Te glasses by Raman spectroscopy and DFT modeling

“…Recently, the telluride systems have attracted a great deal of interest. [1][2][3][4][5][6][7] Mainly it is related to semiconductormetal transition phenomena 1,2,4 and reversible glasscrystal transitions 5,6 in the frame of phase-change memory effect. Understanding the nature of these effects is closely connected with the local structural ordering in telluride glasses.…”

General Approach to the Nucleation and Crystal Growth in Sb0.5Se99.5 Glass Explaining the Shape of DSC Curves

“…Appropriate prediction of crystallization process allows controlling and optimizing of conditions for new high-tech material production. Crystallization behavior can be studied directly by observing of crystals growing in material under specific conditions 4,6 or indirectly by monitoring specific properties of studied material 3,[7][8][9] . The direct observation of crystal growth is very time consuming, thus the indirect methods are preferred.…”