Effect of Dy³⁺ on the physical, optical and radiative properties of CaSO₄–B₂O₃–P₂O₅ glasses

The unprecedented attributes of the trivalent rare earth ions-doped sulfoborophosphate glasses have led to tremendous interest in exploring their potentials for application in diverse photonic devices. Calcium sulfoborophosphate glasses doped with dysprosium ions were prepared by a melt-quenching technique with varying concentrations of Dy³⁺ that range from 0.1 to 1.0 mol%. Amorphous nature of the prepared glasses was determined using X-ray diffraction, while the presence of BO₃, BO₄, P–O–P, PO₄, P–O–B, O–P–O, SO₄ and B–O–B units was determined via FTIR study. Glass density and molar volume were found to be between 2.203 to 2.222 g cm⁻³ and 48.10 to 48.80 m³ mol⁻¹, respectively. The direct and indirect bandgap and Urbach's energy were found to be within 4.183–4.312 eV, 3.423–3.718 eV and 0.381–0.447 eV energy ranges, respectively. The absorption spectra displayed nine prominent peaks centered at 351, 383, 451, 752, 799, 896, 1090, 1269 and 1670 nm corresponding to ⁶H_15/2 → ⁶P_7/2, ⁴F_7/2, ⁴I_15/2, ⁶F_3/2, ⁶F_5/2, ⁶F_7/2, ⁶F_9/2, ⁶H_11/2 and ⁶H_11/2 transitions. The emission spectrum of calcium sulfoborophosphate glasses doped with Dy³⁺ shows two prominent bands at 482 nm (⁴F_9/2 → ⁶H_15/2) and 572 nm (⁴F_9/2 → ⁶H_13/2) and two weak bands at 661 nm (⁴F_9/2 → ⁶H_11/2) and 684 nm (⁴F_9/2 → ⁶H_9/2) under 345 nm excitation. The calculated bonding parameters (δ) were found to be ionic in nature. Judd–Ofelt parameters Ω_λ (λ = 2, 4 and 6) have been calculated from the absorption spectra. The emission cross sections, as well as the branching ratios for two intense emission transitions ⁴F_9/2 → ⁶H_15/2 and ⁴F_9/2 → ⁶H_13/2, have been calculated. The excellent features demonstrated by the present glasses amplify their suitability for solid-state lasers, nonlinear optical and white LEDs applications.