Structure, Judd-Ofelt analysis, and spectral characteristics of terbium doped P2O5-B2O3-ZnO-SrO glasses for green lasers and trichromatic white light-emitting diodes

The Tb ³⁺ doped P ₂O ₅-B ₂O ₃-ZnO-SrO (PBZS system) glasses were prepared by the melt-quenching method. The structural, physical, thermal, and optical properties of the Tb ³⁺ doped PBZS glasses are thoroughly investigated. The thermal behaviour shows that the PBZS system exhibits a higher thermal stability. FTIR and Raman spectra reveal that the lower OH ^- content and phonon energy favors the fluorescent properties. XPS analysis reveals that the Tb ions predominantly exist in the trivalent state. The Judd-Ofelt theory indicates a higher covalency between the Tb ³⁺ and O ^2- ions. Based on the excitation spectra, the phonon sideband characteristics of Tb ³⁺ are observed, which has rarely been reported in previous studies. Under 378 nm excitation, all the glasses display cold and intense green emissions. The spectral results indicate that the optimum doping content of Tb ₂O ₃ is 1.5 mol%, at which point the quantum yield is 29.67 %, and even reaches or exceeds those of the Tb ³⁺ doped glass-ceramics (28.62 %). The energy transfer between the Tb ³⁺ ions is mainly dominated by the dipole-dipole interactions. The lifetimes obtained are all at the millisecond level. Time-resolved emission spectra confirm the photoluminescent stability of the Tb ³⁺ ions. The PBZS glass doped with 1.5 mol% Tb ₂O ₃ presents the higher branching ratio (71.69 % >> 50 %), emission cross-section (2.20 × 10 ⁻²¹ cm ²), gain bandwidth (2.09 × 10 ⁻²⁷ cm ³), and optical gain ( ³.54 × 10 ⁻²⁴ cm ²·s). A nearly negligible chromaticity shift (0.94–2.33 × 10 ⁻²) in 293–473 K that the Tb ³⁺ doped PBZS glasses feature excellent thermochromic properties and thermal stability. The PBZS glass doped with 1.5 mol% Tb ₂O ₃ is a potentially preferable fluorescent material for exploiting green lasers and trichromatic white light-emitting diodes (WLEDs).