Structural, thermal, and luminescence properties of cerium-fluoride-rich oxyfluoride glasses

Oxyfluoride aluminosilicate glasses containing a high nominal concentration of 35 mol% LaF₃ and CeF₃ were synthesized, and their structural, thermal, optical absorption, photoluminescence, radio-luminescence, and excited-state relaxation properties were investigated. The structural analysis confirms the amorphous nature of the glasses and finds up to 21 mol% of retained dissolved LaF₃ and CeF₃. Tetrahedral Si and Al units as well as Si-O-Si and Al-O functional groups are identified. Fluorine is found to replace bridging oxygens and to form both Si-F and Al-F bonds. Glass transition temperature (T_g), crystallization temperature (T _c), and melting temperature (T_m) were determined from the DSC thermograms. The CeF₃-doped glasses show spectrally broad 5d → 4f luminescence in the violet-blue (centered around 402 nm) under both direct optical excitation of Ce³⁺ at 335 nm and X-ray excitation at 25 keV. The relative quantum yield was found to decrease with increasing CeF₃ concentration due to energy transfer to residual Ce⁴⁺ ions or to Ce³⁺ coordinated to hydroxyl (OH) impurities followed by non-radiative relaxation. The studied glasses are promising starting materials for the fabrication of glass-ceramics with a high volume fraction of LaF ₃:Ce³⁺ nano-crystals.