Correlating Structural Disorder and Pr3+ Emission Dynamics in Lu3Al2.5–xScxGa2.5O12 Crystals: A Comprehensive Structure–Property Investigation
来源：ACS Publications
This study explored the influence of Sc3+ ions incorporation on the structural, vibrational, luminescent, and scintillation properties of Pr3+-doped Lu3(Al, Sc)2.5Ga2.5O12 garnet crystals. Addressing the limited research on Sc-admixed and Pr3+ 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 Pr3+ 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 × 107 and 1 × 1011 s–1, consistent with first-order thermoluminescent kinetics. From a materials design perspective, Sc3+ ions substitution induced beneficial host lattice disorder, enhancing the emission intensity of 4f15d11 → 4f2 interconfigurational and 4f2 → 4f2 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 Pr3+ ions offering new opportunities for engineering scintillators and phosphors with tunable optical properties.
The primary objective of this investigation is to elucidate the systematic modulation of band gap energy in Lu3(Al,Ga)5O12 crystals through progressive Sc incorporation, building upon previously established Ga-induced modifications of the conduction band minimum (CBM). This research specifically examines the effect of Sc substitution on the further band gap engineering. The comprehensive study investigates the impact of systematic Sc incorporation in Pr3+-doped Lu3Al2.5–xScxGa2.5O12 garnets across multiple critical parameters: (i) photoluminescence (PL) and scintillation characteristics of Pr3+ emission centers, (ii) vibrational spectroscopic features, (iii) perturbations in the host lattice configuration, (iv) crystal growth dynamics, and (v) radial compositional homogeneity of the synthesized crystals. The systematic variation of Sc3+ ion concentration enables detailed analysis of energy transfer mechanisms to Pr3+ ions and their subsequent impact on the luminescence and scintillation properties. A series of Pr3+-doped Lu3Al5–xScxGa2.5O12 (Pr 0.1 at. %) single crystals with varying Sc3+ concentrations (x = 0.00, 0.10, 0.25, 0.50, 0.75, 1.00) were synthesized via the micropulling-down (μ-PD method). Structural characterization was conducted using powder X-ray diffraction (PXRD), while the crystal microstructure, elemental distribution, and Sc-induced lattice distortions were investigated through complementary SEM–EDS analysis and Raman spectroscopy. Optical absorption, PL, and scintillation parameters were evaluated as functions of the increasing Sc concentration. Thermoluminescence investigations were employed to characterize the Sc influence of the charged trap density and their influence on scintillation dynamics. This investigation discovers the fundamental role of controlled lattice disorder in modulating material properties, providing crucial insights for future materials design. The systematic approach to lattice disorder engineering presents novel opportunities for enhancing the material performance in applications spanning optoelectronics, solid-state illumination, and biomedical imaging.