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

Optical properties of Na2Pb8(PO4)6 : Eu3+, an apatite with anion-free channels, have been investigated at about 20 K by using both selective and time-resolution spectroscopies. Three discrete minor sites are revealed, the spectroscopic features of one of them being consistent with a 4f location of Eu3+. The major sites ascribed to Eu3+ in the 6h positions are distributed. They exhibit unusual spectra as those previously reported for some apatites. The main features are: high position of the 5DJ levels, large value of the Stark splitting to overlap the 7F1 and 7F2 manifolds and a very strong forbidden 5D0→7F0 line. Features are discussed in terms of a Eu–O bond in a point symmetry close to C∞v. Depending upon the site of the distribution, a more or less important coupling occurs between the uppermost 7F1 manifold and the two lowest 7F2 manifolds.