Optical studies of Dy2O3 doped phosphate glasses for potential white luminescence applications

Phosphate glasses with chemical compositions of (60-x) P₂O₅-15ZnO-15CaCO₃-10Li₂CO₃-xDy₂O₃ (where x = 0, 0.25, 0.5, 0.75 and 1 mol %) have been synthesized by melt quenching method. The prepared glasses were characterized by various techniques such as X-ray powder diffraction (XRD), Atomic Force Microscopy (AFM), Differential Scanning Calorimetry (DSC), Fourier Transform Infrared Spectroscopy (FTIR), photoluminescence (PL) and Judd-Ofelt (JO) theoretical model. X-ray diffraction indicates that all samples have an amorphous structure. The Atomic Force Microscopy (AFM) observation of PZCL revealed smooth surface and high quality, characterized by specific roughness parameters (R_a = 2.540, R_z = 11.441, R_max = 13.961, R_q = 3.100 nm) and presented in the form of 3D,2D surface topography. DSC measurements show that PZCLD1 have a good thermal stability among the sample and reached ΔT = 148 °C after adding Dy³⁺. The FTIR spectra confirming an increase of non-bridging oxygen (NBO) by addition of Dy₂O₃. The emission spectra presented three main bands at 491, 575 and 673 nm corresponding to the ⁴F_9/2 → ⁶H_15/2, ⁴F_9/2 → ⁶H_13/2 and ⁴F_9/2 → ⁶H_11/2 transitions, respectively. The luminescence concentration quenching point is observed at 0.5 mol % of Dy₂O₃. The Judd–Ofelt (JO) theory was applied to the absorption bands to determine the phenomenological parameters (Ω₂, Ω₄ and Ω₆ calculated subsequently). It was discovered that the JO parameters are in the following order: Ω₂> Ω₄> Ω₆. These parameters were then used to evaluate key radiative properties, including the total spontaneous transition probability (A_T),the stimulated emission cross-section (σ_e), effective bandwidth (Δλ_eff),the radiative lifetime (τ_rad) and the radiative branching ratio (β_rad) for excited luminescent states. The radiative lifetime of PZCLD0.5 τ_rad = 1.31 ms calculated by Judd–Ofelt theory and experimental lifetime $\tau$_exp = 0.98 ms for the level ⁴F_9/2 decreases as Dy³⁺ concentration increases. Moreover, the quantum efficiency (η = 74.80 %) of PZCLD0.5 indicates that the present material holds strong potential as a candidate for laser emission at 575 nm. The CIE coordinates is found to be x = 0.333 and y = 0.334 revealed that the present sample falls within the white region. The typical CCT value of PZCLD0.5 is estimated to be around 5471 K.