| Nowadays the energy saving and environment protection draw increasing attentions. By virtue of the high energy, utilization, conversion efficiency, long lifetime, small in volume size, fast responding, recycling, non-pollution and easily maintaining, white light emitting diode (WLED) is hailed as the fourth generation lighting source. It has extensively applied in the special lighting field, such as landscape of the city, commercial big screen, traffic signal lamps, mobile phone and LCD backlight, etc. Researching on the WLED phosphors gradually become the exploring focus. (Ba, Ca)2SiO4 Eu2+, Mn2+ is one of the single matrix white phosphors materials for WLED with great developmental potential.In this paper, Ba1.2Ca0.8-xSiO4:xEu2+ (x= 0.02,0.04,0.06,0.08,0.10) blue-green phosphors were prepared by hydrothermal method and co-precipitation method with MCM-41 as silica source. The results show that the hexagonal Ba1.31Ca0.69SiO4 phase can be formed at 800℃ by both of the two methods. The samples prepared by co-precipitation method show better luminescent properties. For the samples calcined at 800℃-1100℃, the intensities of Eu2+ emission band of 430nm-550nm increase with temperature at first and then decrease. The sample calcined at 1000℃ has the highest Eu2+emission intensity. The emission intensity rises with the increase of x value from 0.02 to 0.06, and then, falls gradually with the x value increasing from 0.06 to 0.08.Ba1.2Ca0.68SiO4:0.10Eu2+,0.06Mn2+ and Ba1.3Ca0.68-xSiO4:0.02Eu2+, xMn2+ (x= 0.03,0.06,0.09) white phosphors were prepared by using co-precipitation method. The emission spectra consist of blue-green light of 430-550 nm and red light of 550-650 nm, attributed to 4f65d-4f7 transition of Eu2+ and 4T1(4G)â†'6A1(6S) transition of Mn2+, respectively. With the increase of calcination temperature, the peak maximum of blue-green emission shows red shift and the profile of blue-green emission tend to be more symmetrical. The red emission of Mn2+ arises from the excitation by the Eu2+ emission. The intensity increases sharply with temperature and slowly with the increase of Mn2+ doping content. The Eu2+ ions which can transfer energy to Mn2+ are mainly on the sites of ten-coordinated. The white phosphors with different color coordinates and color temperatures can be synthesized by controlling the calcination temperature and the doping content of Mn2+ can get different color coordinates and color temperature of white ligh.Ba1.2Cao0.64-1.5xSiO4:0.10Eu2+,0.06Mn2+, xY3+(x=0.04,0.08,0.12) and Ba1.2Ca0.64-xSiO4:0.1Eu2+,0.06Mn2+, xDy3+(x=0.01,0.02,0.03) phosphors were prepared by using co-precipitation method. The results show that Y3+ and Dy3+ can significantly sensitize Eu2+ emission. For the samples calcined at 1100 ℃, when the doped content of Y3+is 0.04 and 0.08, the intensities of Eu2+ blue-green emission are respectively 2.5 and 3.2 times of that value of the sample with x=0, and the red emission of Mn2+ increase slowly. When the doped content of Y3+ increase to 0.12, the intensity of blue-green emission falls sharply and the red emission increases sharply, which leads to the white-emitting color shift towards red. Doping Y3+ is favorable to prepare white phosphors at low temperature. When the Y3+ doping content is 0.08, the color coordinates of samples calcined at 900,1000,1000℃, are (0.3308,0.3133), (0.3013,0.3164), (0.3202,0.3461), and the color temperature are 5580K,7330K and 6040K, respectively. With the increase of the doped contenet of Dy3+, the intensity of Eu2+blue-green emission increase significantly, but the Mn2+red emission, which shows an unobvious shoulder peak, are not significantly increased, the white-emitting color shift towards green. |
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