Template-free Hydrothermal Synthesis of Hierarchical Structure CaWO4 Microsphere and its Fluorescence Property

Monodispersed, uniform, and hierarchical calcium tungstate (CaWO4) microsphere structures were synthesized through a template-free hydrothermal synthesis using calcium chloride (CaCl2) and sodium tungstate dihydrate (Na2WO4•2H2O) as precursors, sodium phosphate dodecahydrate (Na3PO4•12H2O) was used as structure-directing agent. The obtained samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). A possible formation mechanism of the spherical CaWO4 was proposed based on the experimental results. In addition, the fluorescence properties of the CaWO4 were studied. Experiment results indicated that the obtained CaWO4 microspheres were assembled by nanoparticles of 30-100 nm in diameter, PO4 3- played a crucial role in the self-assembly process of the hierarchical structure. Moreover, CaWO4 microspheres showed good fluorescence performance.