Structural evolution and thermophysical properties of Tb3ScxAl5-xO12 melts via AIMD and aerodynamic levitation

Abstract

High-power magneto-optical devices based on terbium garnet crystals require materials with high thermal stability and excellent optical performance. However, their growth is often hindered by instability in high-temperature melts. Here, we combine ab initio molecular dynamics (AIMD) simulations and aerodynamic levitation (ADL) experiments to investigate structure–property relationships in Tb 3 Sc x Al 5-x O 12 (x = 0–2) melts. Sc 3+ substitution modifies the Al-O and Tb-O local coordination environments and introduces highly coordinated ScO 5-7 polyhedra with distinct connection preferences. These local structural changes modify polyhedral connectivity, promoting edge- and face-sharing interactions and promote the evolution of medium-range topology toward more compact structural motifs with increased small-ring populations. At intermediate Sc content, the coexistence of Al-rich and Sc-containing units enhances medium-range heterogeneity, leading to the highest viscous flow activation energy. Further Sc incorporation promotes more correlated structural organization and reduces the activation energy. Sc substitution also increases melt density and surface tension, while the thermal expansion behavior results from the combined effects of reduced network connectivity and local structural densification. This work highlights the coupled role of local coordination and medium-range topology in governing the thermophysical behavior of garnet melts.