Viscosity of chalcogenide glass-formers

Abstract

Chalcogenide glass-formers are being used in a remarkable range of various optoelectronic, photonics, photoconducting, sensing and memory device applications. The knowledge of viscosity is essential for the processing of any glass-forming material, in particular for the fabrication of precise optical elements, which is the main application field of chalcogenide glasses. This work presents an extensive collection of all available viscosity data for chalcogenides, including the measurement methods. The Mauro-Yue-Ellison-Gupta-Allan (MYEGA), Arrhenius and VFT equations are used to fit the temperature dependences of viscosity. The viscosity glass transition temperatures, fragilities and apparent activation energies are calculated from these fits. Consequently, these parameters are discussed with regard to the compositional evolution of the respective chalcogenide systems.

Glassy GaS: transparent and unusually rigid thin films for visible to mid-IR memory applications

“…The long-range diffusion/viscous flow, ≳ 1000 K, shows a much higher activation barrier, ≈1.2 eV, comparable with that found in macroscopic viscosity measurements. 91,92 The observed difference is well illustrated by two snapshots of the FPMD simulation boxes taken at 300 K and 1300 K, the insets in Fig. 12(e).…”

Fragility of 1D Floppy Materials

“…The current idea on the 1D liquids may be extended to 0D and 2D materials. For instance, it has been demonstrated that small molecules, e.g., orthoterphenyl, are fragile with m % 80, [6,7,10,14,16] but the character may be affected by intramolecular relaxations. Are elemental van der Waals fluids such as Ar also fragile?…”

“…In brief, related backgrounds can be summarized as follows: It is known that η ( T ) in (supercooled) liquids leading to the glass transition can be approximated using the Vogel–Fulcher–Tammann (VFT) equationwhere η ∞ (=10 −4 P = 10 −5 Pa s) is an empirically chosen viscosity at sufficiently high temperatures, B represents an activation temperature, and T 0 is referred to as the Vogel temperature, which appears to be nearly equal to the Kauzmann temperature T K . In Equation , if T 0 = 0, it reduces to the Arrhenius type, an approximate form appearing in the so‐called “strong” liquid such as SiO 2 .…”

“…[1,2] Among these, the fragility with a steepness index m, which works as a good metric characterizing the viscosity η (¼1/fluidity) variation with temperature T in (supercooled) liquids, [3] has been grasped as an important parameter preluding the glass transition. Actually, extensive studies have been performed for uncovering and understanding relations between the index and other variables including density, [4] elasticity, [5,6] chemical composition, [7,8] enthalpy relaxation, [9] glasstransition temperature, [10][11][12] topological structure, [4,[13][14][15] and stretched exponential factor. [16][17][18] However, still elusive is the interpretation of the fragility in terms of microscopic structures.…”

Analysis of crystal growth and viscosity in Ge-Sb-Se-Te undercooled melts

“…Nevertheless, according to our opinion and experiences, this is the reasonable way to extrapolate viscosity data if melt viscosities are unknown. The different viscosity equations were tested in our work submitted for publishing [39]. Well-described chalcogenide amorphous materials (As2S3, As2Se3, Se) with measured viscosities in melt region were fitted by VFT [40][41][42] (Vogel-Fulcher-Tammann), MYEGA [43] (Mauro-Yue-Ellison-Gupta-Allan) and Ojovan [44] equations.…”