The role of Tb3+ ions, with respect to efficient energy transfer, on sensitization of Gd3+ ions in ( La, Gd) PO4 has been investigated. A series of Tb3+ doped (La, Gd) PO4 were characterized by steady state spectroscopy and efficient energy transfer from Tb3+ 4f(7)5d to Gd3+ 4f (7) states was observed. The decay curves of Gd3+ P-6(7/2) and Tb3+ D-5(3), D-5(4) states upon Tb3+ 4f(7)5d and Gd3+ I-6(J) states excitation were also performed to reveal the energy transfer processes. With the increase of Gd3+ concentration, the energy transfer efficiency increase accordingly. Based on steady state spectra, around 73% energy transfer efficiency in Gd0.99Tb0.01PO4 was determined. (C) 2014 Elsevier B.V. All rights reserved.