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

Abstract

Oxyfluoride aluminosilicate glasses containing a high nominal concentration of 35mol% 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 21mol% 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 (Tg), crystallization temperature (Tc), and melting temperature (Tm) were determined from the DSC thermograms. The CeF3-doped glasses show spectrally broad 5d→4f luminescence in the violet-blue (centered around 402nm) under both direct optical excitation of Ce3+ at 335nm and X-ray excitation at 25keV. 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 LaF3:Ce3+ nano-crystals.