The self-assembly mechanism of CaWO4@CaWO4:Dy3+ core/shell microspheres via a simple surfactant-free hydrothermal route

In this work, we reported the fabrication and characterization of CaWO4@CaWO4:Dy3+ core/shell microspheres via a facile hydrothermal method without organic surfactant. The samples were characterized by XRD, SEM, EDS and photoluminescence. These core/shell microspheres were constructed by nanoparticles through a self-assembly way without any organic surfactant or template. The solid and hollow microspheres prepared through positive and reverse precipitation respectively were used as the precursor. The reduction of the surface energy and high temperature in the hydrothermal process provided the kinetics and thermodynamics motion of the self-assembly course respectively. The direct doped CaWO4:Dy3+ and CaWO4@CaWO4:Dy3+ (core-shell) microspheres show characteristic emission of Dy3+. The luminescent intensity of the core/shell phosphor was enhanced with respect to the direct doped one of the same doping concentration. The possible mechanism was also proposed.