Optical studies of Eu 3+ ions in Bi 4Ge 3O 12 crystals

Abstract

Optical absorption and luminescence spectra of Eu 3+ ions in bismuth germanate Bi 4Ge 3O 12 crystal have been investigated at not only room temperature but also 16 and 10 K, respectively. Sharp absorption lines of Eu 3+ are observed in the spectral region of 350–3300 nm, which are due to the transition from the 7 F 0 ground state. The level assignment has been made for these lines. The luminescence spectra due to the 5 D 0→ 7 F J (J=1, 2, 3, 4, 5, 6) transitions are observed under the excitation from the ground state to the 5 D 0 state. The luminescence decay time is estimated to be 1.76 and 1.55 ms at 10 K and room temperature, respectively. Vibration structure is observed in the luminescence spectrum due to the 5 D 0→ 7 F 1 and 7 F 2 transitions. From the optical spectra, it is confirmed that Eu 3+ ions occupy Bi 3+ sites with C 3 point symmetry.