Eu3 photoluminescence is studied in La5Si 2BO13 with apatite related structure. La 5-xEuxSi2BO13 [x=0.05, 0.1, 0.3, 0.5, 0.7, 1.0, 2.0] compositions are synthesized. The emission results shows that Eu3 ions occupy two different cationic sites viz., La(1) and La(2). The increase in the intensity of 5D0 7F0 line with increasing Eu3 content shows the preferential occupancy of Eu3 in La(2) site due to the existence of short La(2)O(4) (free oxide ion) bond. The observation of antiferromagnetic interactions in Gd and Dy analogues supports the structural features elucidates from photoluminescence studies. © 2010 Published by Elsevier Inc.