Structure and tunable white-light emission of the Ce3+/Dy3+co-doped MgO-K2O-B2O3-P2O5 borophosphate glasses by modulating Mg/K ratio

In this work, the Ce3+/Dy3+ co-doped MgO-K2O-B2O3-P2O5 borophosphate glasses were successfully fabricated by the melt-quenching technique. The structure and optical characteristics were investigated using XRD, DSC, FTIR, Raman spectra, transmittance spectra and photoluminescence (PL) spectra. With increasing Mg/K ratio, the free oxygen introduced by MgO as its contents increase facilitated the conversion of [BO3] triangular units to the denser [BO4] tetrahedral units. The phonon energy of the glass system was estimated to be about 1020 cm-1 from the Raman spectra. Spectroscopic analysis revealed the energy transfer (ET) between Ce3+ and Dy3+ may exist, and the ET between Ce3+ and Dy3+ was explored in detail. Under 315 and 349 nm excitation, the PL spectra disclosed three distinct emission peaks at about 370, 484, and 575 nm, which corresponded to the 5d-4f (Ce3+), 4F9/2 -> 6H15/2 (Dy3+), and 4F9/2 -> 6H13/2 transitions (Dy3+), respectively. The blue shift in the peak position of the cerium ions within the excitation and emission spectra was associated with the decrease in the overall optical basicity of the glass caused by compositional modulation. Tunable white light emission can be achieved by varying the excitation wavelength. Under 349 nm excitation, the optimum chromaticity coordinate (0.325, 0.333) with a correlated color temperature value of 5856 K is obtained at the Mg/K ratio of 3:2, which points to the Ce3+/Dy3+ co-doped MgO-K2O-B2O3-P2O5 borophosphate glasses are a prospective fluorescent material for exploitation of white light-emitting diodes (WLEDs).