Three-dimensional (3D) nanostructured CaWO4:Tb3+ microspheres assembled by submicrospindles were synthesized via a mild sonochemical route from an aqueous solution of CaCl2, TbCl3 and Na2WO4 with the aid of surfactant Polyglycol 600 (PEG-600). The crystal structure and morphology of the as-prepared products were characterized by using X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). Rietveld refinement was carried out on the XRD data. The results showed that the CaWO4:Tb3+ nanoparticles can be formed without ultrasonic irradiation or addition of PEG-600. With continuously increasing irradiation time the submicrospindles and microspheres could be self-assembled. The central diameter and length of the submicrospindles are around 190 and 500 nm, respectively. The 3D CaWO4:Tb3+ nanostructured microspheres with diameter of 2-4 mu m were assembled by the submicrospindles. A possible formation mechanism for the 3D-structured CaWO4:Tb3+ microspheres was proposed. The Photoluminescent (PL) properties of Tb3+ ions in the nanostructured CaWO4 microspheres were studied. The energy transfer processes in CaWO4:Tb3+ microspheres were analyzed. The electric dipole-dipole energy transfers related to D-5(3) level were studied by inspecting the fluorescence decay of D-5(3) level. The energy transfer critical distance was estimated. (C) 2011 Elsevier Inc. All rights reserved.