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Abstract
The medium-range atomic structure of magnesium and barium aluminosilicate glasses doped with Gd2O3 as a model rare earth oxide is elucidated using molecular dynamics simulations. Our structure models rationalize the strong dependence of the luminescence properties of the glasses on their chemical composition. The simulation procedure used samples’ atomic configurations, the so-called inherent structures, characterizing configurations of the liquid state slightly above the glass transition temperature. This yields medium-range atomic structures of network former and modifier ions in good agreement with structure predictions using standard simulated annealing procedures. However, the generation of a large set of inherent structures allows a statistical sampling of the medium-range order of Gd3+ ions with less computational effort compared to the simulated annealing approach. It is found that the number of Si-bound non-bridging oxygen in the vicinity of Gd3+ considerably increases with growing ionic radius and concentration of network-modifier ions. In addition, structure predictions indicate a low driving force for clustering of Gd3+, yet no precise correlation between the atomic structure and luminescence lifetimes can be conclusively established. However, the structure models provided in this study can serve as a starting point for future quantum mechanical simulations to shed a light on the relation between the atomic structure and optical properties of rare earth doped aluminosilicate glasses.
Highlights
Aluminosilicate glasses have widespread use in many different technological fields, e.g., as optical devices, as high strength display glasses, or as precursors for low expansion or bio-glass ceramics.Display glasses are mostly based on sodium aluminosilicate glass compositions [1,2]
The Si-Ba pair distribution functions (PDF) are virtually identical, see Figure 1a. This applies to every other PDF of the network former and modifier ions
MgO are performed for investigation of the atomic medium-range structure of Gd3+ as a function of a network-modifier oxide to Al2 O3 ratio varied between 1 and 3
Summary
Aluminosilicate glasses have widespread use in many different technological fields, e.g., as optical devices, as high strength display glasses, or as precursors for low expansion or bio-glass ceramics. In the past few years, aluminosilicate glasses doped with rare earth ions have been proposed as laser materials [8] They possess excellent thermo-mechanical properties, such as high strength, high hardness, high toughness, and a low coefficient of thermal expansion (CTE) [9] and, a much higher laser damage threshold than conventionally used laser glass compositions such as phosphate and fluoride phosphate glasses [10]. In case of glass compositions with low dopant concentrations of about 1 mol%, the size of the structure models has to be substantially larger (>104 atoms [16]) to achieve a sufficient statistical sampling of the medium-range atomic order of the dopant ions This results in a considerable increase of the computational effort for structure predictions of such glasses. The local surrounding of the Gd3+ ions within these glasses is analyzed in detail
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