Knowledge of viscosity is necessary for calculation of reduced crystal growth rate. Connection between viscosity and cold crystallization which takes place in undercooled melts is also very important. Where G ∞ stands for the shear modulus at infinite frequency. Also structural relaxation time τ is proportional to viscosity η through well known Maxwell equation The connection between viscous behavior and relaxation can be derived from the similarity between apparent activation energies of both processes which was described for example for selenium glass. This process is in fact a very slow flow of material. Structural relaxation is very slow rearrangement of thermodynamically unstable glass toward equilibrium. Viscosity is also important for description of structural relaxation and cold crystallization of glasses and undercooled melts, respectively. Fundamental temperature points necessary for successful preparation of bulk glasses are calculated from temperature dependence of viscosity. Viscosity is one of the basic physical properties and knowledge of it for given material is very important. Also electric induced phase changes of chalcogenides are investigated due to the potential application in memory media. The laser induced changes between crystalline and amorphous phases are used in that case.
Some of them are also well known phase change materials (PCM) which are used for rewritable CD or DVD discs. They can be used as threshold and memory switches or infrared optics elements (detectors, lenses or fibers). Amorphous chalcogenides are interesting materials with unique properties which found many applications, e.g., in electronics and optoelectronics.
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