Optical studies of Eu3+ ions in Bi4Ge3O12 crystals

Optical absorption and luminescence spectra of Eu3+ ions in bismuth germanate Bi4Ge3O12 crystal have been investigated at not only room temperature but also 16 and 10 K, respectively. Sharp absorption lines of Eu3+ are observed in the spectral region of 350-3300 nm, which are due to the transition from the F-7(0) ground state. The level assignment has been made for these lines. The luminescence spectra due to the D-5(0) --> F-7(J) (J = 1, 2, 3, 4, 5, 6) transitions are observed under the excitation from the ground state to the D-5(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 D-5(0) --> F-7(1) and F-7(2) transitions. From the optical spectra, it is confirmed that Eu3+ ions occupy Bi3+ sites with C-3 point symmetry. (C) 1999 Elsevier Science B.V. All rights reserved.