Site-selective spectroscopy of Eu3+-doped sodium lead phosphate apatite

Optical properties of Na2Pb8(PO4)(6) : Eu3+, an apatite with anion-free cha nnels. have been investigated at about 20 K by using both selective and tim e-resolution spectroscopies. Three discrete minor sites are revealed, the: spectroscopic features of one of them being consistent with a 4f location o f Eu3+. The major sites ascribed to Eu3+ in the 6h positions are distribute d. They exhibit unusual spectra as those previously reported for some apati tes. The main features are: high position of the D-5(J) levels, large value of the Stark splitting to overlap the F-7(1) and F-7(2) manifolds and a ve ry strong forbidden D-5(0) --> F-7(0) line. Features are discussed in terms of a EuO bond in a point symmetry close to C-proportional tov. Depending u pon the site of the distribution, a more or less important coupling occurs between the uppermost Fl manifold and the two lowest F-7(2) manifolds. (C) 2001 Elsevier Science B.V. All rights reserved.