Recently, the researchers at the Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, have made significant progress in studying the local structure of rare-earth phosphate glasses. The research team resolved the characteristic coordination environment of Sc³⁺ ions at the atomic scale and clarified their local aggregation mechanism, providing deeper theoretical insight into the structure–property relationships and performance optimization of rare-earth–doped functional glasses. The related work, entitled “Structural Studies of Sc­₂O₃–xKPO₃ Glasses by Solid-State NMR Spectroscopy,” was published in the Journal of Non-Crystalline Solids.

  The optical and thermodynamic stability of rare-earth–doped glasses strongly depend on the local coordination environment and spatial distribution of rare-earth ions. Although previous studies have employed spectroscopic, Raman, and neutron scattering techniques to explore the coordination states of rare-earth ions in glass networks, these methods have shown limited capability in precisely distinguishing and quantitatively characterizing the diverse local configurations of rare-earth species. Moreover, paramagnetic rare-earth ions are generally difficult to probe effectively by solid-state nuclear magnetic resonance (SSNMR), which further constrains in-depth understanding of the bonding mechanisms and structural evolution of rare-earth ions within glass networks. As a result, the local ordering and network-modifying roles of rare-earth ions remain poorly understood.

  In this study, Sc³⁺—a diamagnetic ion with excellent SSNMR responsiveness—was employed as a model to simulate the structural behavior of small-radius heavy rare-earth ions in phosphate glasses. Using advanced multidimensional SSNMR techniques, the local structures of ³¹P, ⁴⁵Sc, and ³⁹K in Sc₂O₃–xKPO₃ glasses were systematically characterized, revealing the coordination features and aggregation behavior of Sc³⁺ ions. The results show that Sc³⁺ exclusively adopts an octahedral six-fold coordination environment and is connected via corner-sharing to six phosphate tetrahedra [PO₄].

  The study explicitly identified the P¹_3Sc   structural unit and quantitatively analyzed nine types of Pⁿ_mSc   species (n = 0, 1, 2; m = 0, 1, 2, 3). Computational analysis based on charge, coordination number, and spatial distribution probability revealed a significant clustering tendency of Sc³⁺ ions within a 5.5 Å range.

  Based on this finding, an atomic-scale clustering model for Sc³⁺ was constructed. This atomic-scale model elucidates the microscopic mechanism of rare-earth ion clustering, thereby establishing a foundation for understanding and modulating the optical and thermal properties of phosphate glasses. Furthermore, it provides guidance for material design to mitigate the risk of phase separation.

  This work was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences.

  Figure 1. Schematic illustration of the spatial distribution of PmScn species surrounding a Sc³⁺ ion in the 1Sc₂O₃-7.5KPO₃ glass.

  Article website: https://authors.elsevier.com/c/1lx~k_WTjy6-I

  Contact: REN Jinjun 

  Advanced Laser and Optoelectronic Functional Materials Department, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences 

  Email: jinjunren@siom.ac.cn