Enhanced emission from Eu3+ in B ions doped sol-gel SiO2 phosphors

Eu single doped and Eu, B co-doped SiO2 xerogels and films were prepared by sol-gel process, using tetraethoxy silane, boric acid and aluminium nitrate as precursors, europium nitrate as the dopant. The influence of B ions and annealing temperature on luminescent properties of phosphors has been studied using fluorescence spectrum, X-ray diffraction and IR spectrum. The phosphors showed prominent luminescent in red. When heated up to 500°C, the emission spectrum showed six characteristic emission peaks, due to the electronic transition of5D0->7FJ (J = 0, 1, 2, 3, 4) for Eu3+ respectively and the electronic transition of 5D0->7F1 was splited two peaks. When B ions were introduced to the Eu doped samples, the red Eu3+ emission was enhanced remarkably. This is because Si-O-B bonds were formed in the luminescent materials, and the symmetry of network was breached. Annealing changed the network structure and reduced the content of -OH and water, which benefits intensity of emission from Eu3+. The intensity of emission from Eu3+ quenches with increasing of annealing (up to 850°C) for probability during the annealing process, the rare earth ions may migrate and form clusters. The clustering process makes the local concentration of Eu very high and causes serious fluorescence quenching. XRD results show that the phosphor is in amorphous phase.