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 D-5(0) level of Eu3+, as well as through the excitation of the D-5(1) level. The Judd-Ofelt theoretical framework was used to compute the radiative lifetimes (tau) and the omega parameters (omega(lambda)). The electric dipole transition probabilities, asymmetry ratios (R), along with the branching ratios (beta) were also determined based on the obtained experimental data. The strongest detected luminescence belongs to the D-5(0) -> F-7(0) transition observed at 578 nm, similar to the BGO sillenite. Reasons for the major presence of the D-5(0) -> F-7(0) emission, theoretically forbidden by the Judd-Ofelt Theory, were investigated and compared with that of the BGO sillenite. Obtained results showed that the strong D-5(0) -> F-7(0) line is also present in Eu:BSO, indicating that this is a feature of the entire sillenite family and not just Eu:BGO.