| White LED is a new-style solid state light source. Presently, it is the main way to make white LED combining with phosphors. And the single matrix white light silicate phosphor has attracted much research interest in the area of illumination due to its superiorities in luminescence properties.Sr2SiO4:Dy3+and Sr2SiO4:Dy3+, Eu3+phosphors for white LED were prepared via sol-gel process. The structure and emission spectra excited by near violet light were investigated.The structure of all the samples were characterized by Powder X-ray diffraction(XRD), the morphologies of the samples were observed by scanning electron microscopy(SEM) and the excitation and emission spectra of samples were obtained using fluorescence spectrophotometer.The excitation spectra of Sr2SiO4:Dy3+show strong absorption near 325nm,350nm,365nm and 386nm due to H15/2→6P3/2,6H15/2→6P7/2,6H15/2→6P5/2,6H15/2→4M21/2 transition of Dy+. The emission spectrum of Dy3+has three groups of emissions located at about 479nm,491nm,571nm under 386nm UV excitation. The emission peaks at 479nm and 491nm (Blue) attribute to the 4F9/2→6H15/2 transition and 571nm (Yellow) attributes to the 4F9/2→6H13/2 transition. The two colors make white light. The effect of Dy3+concentration on the emission spectrum intensity of Sr2SiO4:Dy3+was investigated. The color coordinates (CIE) analysis indicates Sr2SiO4:Dy3+is located at (0.35,0.38) which is near white color region, but not at the best location. Therefore, it is necessary to improve the red light emission.The emission spectrum of Eu3+and Dy3+co-doped Sr2SiO4 phosphors under UV excitation were investigated for enhancing red emission. The emission spectrum consists of three bands. The blue and yellow bands attribute to Dy3+ions and the red band from 610nm to 620nm attributes to the 5D0—7F2 transition of Eu3+ions. The emission intensity of red band is lightly enhanced.The effect of Eu3+concentration on the emission spectrum intensity of Sr2SiO4: Dy3+, Eu3+was investigated. The best doping concentration for white phosphors was achieved when the concentration for Eu3+and Dy3+were 1mol% and 4mol%, respectively. And the corresponding color temperature of the Sr2SiO4:0.04Dy3+, 0.01Eu3+was 5603K. In addition, several experimental factors such as annealing temperature and the condition of the charge compensation, which had influence on the photoluminescence (PL) intensity of Sr2SiO4: Dy3+, Eu3+phosphors were also studied. As the annealing temperature increased from 900℃to 1100℃, the PL intensity was significantly enhanced. However, the PL intensity showed almost no change when the annealing temperature was further increased. The effect of charge compensation on the emission spectra of Sr2SiO4:Dy3+, Eu3+phosphor was also studied. The emission spectra intensity of Sr2SiO4: Dy3+, Eu3+phosphor firstly increased to a maximum value and then began to decrease with the continuously increasing of the charge compensation concentration. Furthermore, different charge compensations showed different effect on the emission intensity, and the most obvious effect was observed when Li+is employed as the charge compensation.There are 23 figures,4tables and 44 references in this paper. |
PDF Full Text Request