Localization effect for doping and collaborative diffusion in Er3+:YAG melt

Abstract

Coordination geometry variations of cations in yttrium aluminium garnet (YAG) melt system doped with various Er³⁺ concentrations were quantitatively simulated at the classical molecular dynamic level. Our calculated radial distribution functions were discussed upon different ionic pairs, mean square displacement, and diffusion coefficient of ions, on which we clarified two important aspects, namely structure and dynamic properties in YAG melts with intermediate-range order (IRO). Our results show that Er³⁺ doping affects microscopic dynamic melt structures only in a confined scale localizing in the first nearest neighbour of Er³⁺ and O²⁻. Furthermore, such a localization effect is not varied with Er³⁺ concentration and system temperature. In the present melt system, Y³⁺, Al³⁺, and Er³⁺ cations with intrinsic differences (such as mass and electronegativity scales) were found to follow the same diffusion process in this system, which is mainly caused by the wholly collective rearrangement of the network-forming structure. In this Er³⁺:YAG melt system, there is an equivalence within both structure and dynamics for Er³⁺ and Y³⁺, which cannot be affected by the system temperature and Er³⁺ concentration, ascribing to the origin of the segregation coefficient of Er³⁺ in YAG to be equal to 1.