Dysprosium ion activated RE3BO6 (RE = La, Y, Gd) polycrystalline phosphors have been prepared via a modified sol–gel process with urea as fuel and rare earth nitrates as precursors. The crystal phase and the morphology of the phosphors are characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The average particle size after heat treatment at 1,000 °C is around 5 μm by particle size determination technique. The characteristic transitions of Dy3+ due to 4F9/2 → 6H15/2 (blue) and 4F9/2. → 6H13/2 (yellow) can be observed in the emission spectra and the yellow-to-blue intensity ratio (Y/B) can be changed with the variety of the doped concentration of Dy3+ ion. Zeta potential shows the relationship between the surface charges to the pH value in suspension.