By substituting Gd3+ for Ba2+ ions in the single-phased Na-2(Ea(5.99-2m)Eu(0.01)Gd Na-m (m))(Si2O7)(SiO4)(2) (0 <= m <= 0.30) phosphors, the asymmetric emission peaks of three Eu luminescence centers monitored around 444, 494 and 552 nm varied accordingly under 365 nm excitation and caused the shift of CIE color coordinates from (0.1569, 0.2122) to (0.1697, 0.3082). Furthermore, the thermal stability and quantum yield of phosphors could be affected via the different cation substitution of Gd3+. Combined with the change tendencies of Ba-O bond lengths by Rietveld refinement, the possible mechanism of the luminescence transformation of Eu2+ ion was the preferential occupancy at different crystallographic sites of Eu2+. Generally, this work sheds some new lights on the design and structure explanation of preferential occupancy at different crystallographic sites in phosphors. (C) 2017 Elsevier Ltd. All rights reserved.