Correlating Structural Disorder and Pr$^{3+}$ Emission Dynamics in Lu$_3$Al$_{2.5–x}$Sc$_x$Ga$_{2.5}$O$_{12}$ Crystals: A Comprehensive Structure–Property Investigation

ABSTRACT: This study explored the influence of Sc$^{3+}$ ions incorporation on the structural, vibrational, luminescent, and scintillation properties of Pr$^{3+}$-doped Lu$_3$(Al,Sc)$_{2.5–x}$Ga$_{2.5–x}$O$_{12}$ garnet crystals. Addressing the limited research on Sc-admixed and Pr$^{3+}$ doped garnet systems, this work successfully demonstrated the crystallization of garnet crystals from the melt, overcoming the substantial atomic mismatch between Sc and Al while preserving the thermodynamic stability of the garnet phase. Importantly, Sc-admixing enhanced atomic homogeneity and allowed for increased doping concentrations of Pr$^{3+}$ ions, which is crucial for tailoring the functional properties of advanced optical materials.The trap depths ranged from 1.63 eV (deep traps) to 0.22 eV (shallow traps) across all samples, with frequency factors predominantly between 1 × 10$^7$ and 1 × 10$^{11}$ s$^{−1}$, consistent with first-order thermoluminescent kinetics. From a materials design perspective, Sc$^{3+}$ ions substitution induced beneficial host lattice disorder, enhancing the emission intensity of 4f$^1$5d$_1$ $^1$ → 4f$^2$ interconfigurational and 4f$^2$ → 4f$^2$ intraconfigurational transitions. This effect highlighted the potential of Sc as a promising substituent for enhancing the luminescence intensity of rare earth elements.Synchrotron radiation experiments provided insights into the impact of Sc on band gap energy and energy transfer efficiency toward Pr$^{3+}$ ions offering new opportunities for engineering scintillators and phosphors with tunable optical properties.