Ba₅Zn₄Gd₈O₂₁:Tb³⁺-structural characterization and the Judd-Ofelt parameterization from emission spectra

Ba₅Zn₄Gd₈O₂₁:Tb³⁺ nanorods; synthesized via solution combustion route; were found to crystallize in the tetragonal (I4/m, 87) crystal system. The UV excitation at 290 nm of all Ba₅Zn₄Gd₈O₂₁:Tb³⁺ samples yielded the characteristics emission corresponding to ⁵D₄ → ⁷F_6,5,4,3 transitions in Tb³⁺ activator (used for Judd-Ofelt analysis). A detailed investigation of photoluminescence decay curves and emission spectra of Ba₅Zn₄Gd₈O₂₁:Tb³⁺ nanorods provided the radiative lifetime (1.0889 ms) and total radiative transition rates from ⁵D₄ state in Tb³⁺ ion. The electric-dipole radiative transition probabilities (extracted from total radiative rates i.e. electric-dipole + magnetic-dipole) were used to calculate the Judd-Ofelt intensity parameters (Ω₂ = 4.76 × 10^-20, Ω₄ = 2.11 × 10^-20 and Ω₆ = 2.00 × 10^-20 cm²). The very high quantum efficiency of ⁵D₄ state (81%) suggests their potential use in lighting and display devices. Finally, a large magnitude of peak stimulated emission cross section of ⁵D₄ → ⁷F₅ (16.5838 × 10^-20 cm²) transition also claims their promising candidature as a good laser material.