Site-selective cation distribution and structural distortion in Y3Al5−xGaxO12:Pr garnet phosphors: a multi-analytical investigation

This study presents a comprehensive investigation into the site-selective distribution of Ga3+ and Al3+ cations within the tetrahedral (16d) and octahedral (24f) sites of the Y3Al5-xGaxO12:Pr garnet series. By integrating X-ray powder diffraction (XRD), solid-state NMR (nuclear magnetic resonance) spectroscopy, and density functional theory (DFT) calculations, we elucidated the site occupancy preferences across the compositional range. Our results provide a consistent structural model, demonstrating that Ga3+ ions exhibit a clear preference for tetrahedral sites over octahedral ones. Furthermore, we reveal that while XO6 octahedra undergo pronounced structural distortion in mixed Al-Ga compositions, the XO4 tetrahedra remain remarkably resistant to deformation. These findings establish a fundamental framework for structural modeling and provide critical insights for tailoring the luminescence performance of garnet-based phosphors through strategic site engineering. The methodologies and structural principles derived here are readily applicable to the design of other complex mixed-cation host lattices.