Structural and luminescence properties of Dy³⁺-doped alkali fluoroborophosphate glasses for white LEDs applications

Abstract

A new series of Dy³⁺-doped alkali fluoroborophosphate glasses were prepared by conventional melt quenching technique, and their structural and optical properties were investigated through XRD, FTIR, optical absorption, luminescence and decay measurements. The X-ray diffraction pattern reveals the amorphous nature of the prepared glasses. The fundamental stretching vibrations of various borate (BO₃ and BO₄) and phosphate (PO₄) networks were identified through the FTIR analysis. The nature of the metal–ligand bonding and the electronic band structure has been investigated using the absorption spectra. The Judd–Oflet (JO) intensity parameters (Ω₂, Ω₄ and Ω₆) were evaluated, and the experimental oscillator strength values were also calculated. Using the JO intensity parameters, radiative properties like radiative transition probability (A) stimulated emission cross section $\left( {\sigma_{\text{p}}^{\text{E}} } \right)$ and branching ratios $\left( {\beta_{\text{R}} } \right)$ for the emission transitions of the Dy³⁺ ions have been calculated. The luminescence spectra exhibit two visible bands of ⁴F_9/2 → ⁶H_15/2 (Blue) and ⁴F_9/2 → ⁶H_13/2 (Yellow). The decay time of the ⁴F_9/2 level has been measured from the decay profiles and compared with the calculated lifetimes. The yellow-to-blue (Y/B) ratios and color coordinates have been calculated from the luminescence spectra and can be considered for white light emitting diodes applications.