The orthorhombic and monoclinic Gd-2(MoO4)(3):Dy3+ were successfully synthesized by a hydrothermal process with a subsequent annealing treatment at 800 degrees C for 4 h. The crystal phase of Gd-2(MoO4)3:Dy3+ was controlled as a function of the pH value of the solution. The crystallization and microstructures of the samples were characterized by Powder X-ray diffraction (XRD) and scanning electron micrograph (SEM). Furthermore, the optical properties were investigated by the diffuse reflection, excitation and emission spectra. The mechanisms of different crystal phases affected on the luminescence properties of Gd-2(MoO4)3:Dy3+ were discussed. The electric dipole-dipole interaction between Dy3+ ions was identified as the main mechanism for the concentration quenching of the two structures. Finally, the chromatic natures of all the samples were analyzed in detail. The results indicate that the orthorhombic phosphor Gd-1.84(MoO4)(3):Dy-0.16(3+) can be considered as a suitable candidate for white light emitting diodes (W-LEDs). (C) 2012 Elsevier Ltd. All rights reserved.