Optical studies of Eu3+ ions in Bi4Ge3O12 crystals

Optical absorption and luminescence spectra of Eu3+ ions in bismuth germana te Bi4Ge3O12 crystal have been investigated at not only room temperature bu t also 16 and 10 K, respectively. Sharp absorption lines of Eu3+ are observ ed in the spectral region of 350-3300 nm, which are due to the transition f rom the F-7(0) ground state. The level assignment has been made for these l ines. 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 a nd 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.