EU3+ luminescence -: a structural probe in BiCa4(PO4)3O, an apatite related phosphate

Eu3+ luminescence is studied in apatite-related phosphate BiCa4(PO4)(3)O. Compositions of the formula Bi1-xEuxCa4(PO4)(3)O [x = 0.05, 0.1, 0.3, 0.5, 0.8 and 1.0] are synthesized and they are isostructural with parent BiCa4(PO4)(3)O. Room temperature photoluminescence shows the various transitions D-5(0) --> F-7(J( = 0.1,2)) of Eu3+. The emission results of compositions with different Eu3+ content show the difference in site occupancy of Eu3+ in Bi1-xEuxCa4(PO4)(3)O. The intense D-5(0) - F-7(0) line at 574 nm for higher Eu3+ content is attributed to the presence of strongly covalent Eu-O bond that is possible by substituting Bi3+ in the Ca(2) site. This shows the preferential occupancy of Bi3+ in Ca(2) site and this has been attributed to the 6s(2) lone pair electrons of Bi3+. This is further confirmed by comparing the emission results with La0.95Eu0.05Ca4(PO4)(3)O. (C) 2004 Elsevier Inc. All rights reserved.