Synthesis and characteristics of nano-size sandwich structure (Y,Gd)BO3: Eu3+ phosphors

The sandwich structure core–shell–shell nanospheres SiO2@(Y,Gd)BO3:Eu3+@SiO2 (SiO2@YGB@SiO2) have been synthesized by depositing YGB nanoparticles on silica core surface through the precipitation method, followed by sol–gel processing of tetraethoxysilane (TEOS) to form smooth silica shell over the surface of YGB. The phosphors were characterized by X-ray diffraction (XRD), scanning electronic microscope (SEM), transmission electronic microscope (TEM) and photoluminescence spectra. The results showed that the phosphors with spherical morphology can be produced easily by assembling the core–shell or core–shell–shell structure, and the XRD patterns indicated that the crystallinity of YGB is weakened due to the core–shell structure, which resulting from the local site symmetry of Eu3+ was decreased. The photoluminescence properties of the product are compared with those of the pure YGB, the core–shell structure SiO2@YGB and YGB@SiO2. The emission intensity, relative luminous efficiency and Red/Orange values of phosphors are increased in the order SiO2@YGB@SiO2>SiO2@YGB>YGB@SiO2>YGB; and the chromaticity coordinates of the phosphors are shifted from orange of pure YGB to red of SiO2@YGB@SiO2.