Luminescence of some lanthanide activators in NaBi(MoO₄)₂

NaBi(MoO₄)₂ activated with trivalent lanthanides Tb and Nd was synthesized and results on luminescence are presented. Characteristic emission of the lanthanide activators is observed. A weak band could be seen in the excitation spectra which is distinct from the f–f lines. This band appears at a position almost same as that observed in the reflectance spectra. Hence, it is proposed that there is host sensitization, even though weak, of the lanthanide luminescence in this host. The sensitization is due to Bi³⁺ → Ln³⁺ and/or Mo–O → Ln³⁺ energy transfer. In case of Tb³⁺, the excitation spectrum is unique, in that the most effective excitation could be achieved only through ⁷F₆ → ⁵D₄ transition. Using the results on the concentration quenching, the “critical distance for energy transfer” among activator ions is estimated as about 18.3 Å.