A Comparative Study of Eu³⁺-Doped Sillenites: Bi₁₂SiO₂₀ (BSO) and Bi₁₂GeO₂₀ (BGO)

The spectroscopic properties of Eu³⁺-doped Bi₁₂SiO₂₀ (BSO) were investigated and compared with that of Eu³⁺-doped Bi₁₂GeO₂₀ (BGO). The emission properties and the absorption spectra have been measured at 10 K as well as at 300 K (room temperature). Luminescence was detected due to the direct excitation of the ⁵D₀ level of Eu³⁺, as well as through the excitation of the ⁵D₁ level. The Judd-Ofelt theoretical framework was used to compute the radiative lifetimes (τ) and the omega parameters (Ω_λ). The electric dipole transition probabilities, asymmetry ratios (R), along with the branching ratios (β) were also determined based on the obtained experimental data. The strongest detected luminescence belongs to the ⁵D₀ → ⁷F₀ transition observed at 578 nm, similar to the BGO sillenite. Reasons for the major presence of the ⁵D₀ → ⁷F₀ emission, theoretically forbidden by the Judd-Ofelt Theory, were investigated and compared with that of the BGO sillenite. Obtained results showed that the strong ⁵D₀ → ⁷F₀ line is also present in Eu:BSO, indicating that this is a feature of the entire sillenite family and not just Eu:BGO.