Silica Luminescent Materials Preparation And Performance

Eu-doped SiO₂ matrix xerogels and thin films were prepared by the sol-gel process and the hydrothermal synthesis method. The samples were characterized by fluorescence spectrum, transmission electron microscope (TEM), scanning electron microscope (SEM), atomic force microscope (AFM) and infrared absorption (IR) spectrum etc. The effect of precursors' ratio, doping concentration, annealing temperature etc. on the microstructure, surface topography and luminescent property of Eu³⁺ and Eu²⁺ ions doped SiO₂ were investigated. The mechanism of luminescence was studied.The xerogels prepared by the sol-gel were uniform and their particle size was about 50-80 nm. The network structure of the matrix was changed by the process of Boron (B) ions enter into the SiO₂ grid, corresponding to the formation of Si-O-B. With the increase of annealed temperature, the intensity of the red light emission at first enhanced then weakened excited at 258nm. The red luminescent intensity of the sample annealed at 800℃was the strongest. The spectrum showed three peaks, 576nm (⁵D₀→⁷F₀) ,620nm (⁵D₀→⁷F₂) ,658nm (⁵D₀→⁷F₃) . The strongest red emission band centered at 620nm was due to the ⁵D₀→⁷F₂ transition of Eu³⁺. The blue luminescent intensity of the samples annealed at 850℃reached the strongest at the excitation wavelength of 271nm. The strongest blue emission band centered at 400-500nm was due to the 5d→4f transition of Eu²⁺. In the presence of Al³⁺, Eu³⁺ was reduced to Eu²⁺ by the process of high temperature annealing. Under the vacuum annealed process at 1450℃, with the increase of doping concentration, the blue emissions of the samples first increased and then weakened, and also the spectral lines shifted to red. When the doped quantity of Eu is 0.4%, its intensity was the strongest.The spin-coating thin films were prepared by the sol-gel technique, whose surface is uniform and small ups and downs. The annealing treatment can improve the uniformity of thin films. When the films were excited at 258nm, double peaks were observed, which was rarely seen. And the emission intensity of ⁵D₀→⁷F₂ reached the strongest, which suggested Eu³⁺ ions lay in the coordination environment of the lower symmetry. The annealing temperature made great effect on the emission spectroscopy. The luminescent intensity of the films annealed at 900℃was the strongest The surface roughness of the films prepared by the hydrothermal method was larger. The spectrum of thin films excited at 262nm showed the 615nm and 674nm emission peaks. The luminescent intensity of the samples annealed at 850℃was the strongest. And, the luminescent intensity of the films doped with Al³⁺ ion decreased obviously. When the xerogels were excited at 258nm, double peak were observed, which was the 615nm and 578nm emissions and the intensity of the xerogels annealed at 750℃was the strongest.