Eu3+激活的硼钒酸钇的光致发光

找出了合成Eu3+激活的硼钒酸钇铕发光粉的适宜条件和发光最佳化学组分,它是(Y0.94Eu0.06)(V0.69B0.31)O3.7.对其发光光谱的温度依赖关系的研究指出,发光最佳温度在350℃左右.发光的这种温度依赖关系与基质和Eu3+对能量的吸收,以及基质向Eu3+能量传递效率的提高有关.此外,试验结果还表明,在365nm激发下,少显Gd2O3、Zn2GeO4·GeO2:Mn2+等添加剂的加入提高了样品的发光亮度.

PHOTOLUMINESCENCE OF Eu3+-ACTIVATED YTTRIUM BORATOVANADATE

Boric anhydride (B2O3) is a compound rather strong in acidity. At given temperatures, it can be co-soluble with the metal oxides of alkaline earth, alkali, molybdenum or vanadium, and yeild glassy or solid solutions. In this experiment, europium yttrium boratovanadate phosphor has been synthesized using yttrium boratovanadate as the host and europium as the activator. Photoluminescence behaviour has been studied.Appropriate experimental conditions for synthesizing the phosphor and optimal compositions for luminescence, (Y0.94Eu0.06) (V0.69B0.01)O3.7, were found out. Adding small amount of rare-earth impurity, e.g.Gd2O3, Sm2O3, has little effect on or a slight enhancement of the europium luminescence under 365nm excitation. However, adding luminescent compounds such as Zn2GeO4. GeO2:Mn and SrLaBO4:Pb has markedly enhanced the europium luminescence. This is ascribed to the overlap of the emission bands of the added compounds with the absorption bands of europium. Adding Bi3+ to the phosphor results in a great increase of the luminescence intensity. The excitation band of Bi3+ -containing sample is broadened with peak shifted toward the longer wavelength side. The emission band of Bi3+ peaking at 539nm can be seen in the emssion spectrum (fig. 3). The increase of the luminescence intensity is therefore attributed to the summing up of the Bi3+ and Eu3+ emission.The peak of the excitation band of Eu3+ is at 326nm, corresponding to the excitation transition of the cluster VO43-, and the band may overlap with excitation band of the charge transfer state of Eu (fig. 1,2). Besides, lines at 383, 396, 418, 467 and 539nm in this band correspond to the excitation from 7F0 to 5D4,5L6, 5D3, 5D2, 5D1.The emission spectrum of Eu is composed of the lines at 594, 610, 616, 619, 699 and 705nm, the most intense ones are at 616 and 619nm, corresponding to the transition from 5D0 to 7F2.By the investigations of the emission spectra of the sample under different temperatures, it is pointed out that the optimal temperature for luminescence is about 350℃ (fig.5). The effect of temperature on luminescence depends on the energy absorption by the host and Eu, as well as on the increased efficiency of energy transfer from the host to Eu. Below 350℃, the luminescence intensity increases rapidly with the increasing temperature; above this temperature, the decrease follows. It is supposed that Eu can be efficiently excited by ultraviolet light to the charge transfer state(4f72p-1). With the increase of temperature, the charge transfer state lowers down and the absorption band shifts toward longer wavelength side, nearer to the excitation wavelength 324nm of VO43-; whereas the lowered energy level gets nearer to the 4f excited state, thus increase the probability of relaxation to the 4f excited state (the number of phonons corresponding to the energy difference between the two states decreases) resulting in the increase of luminescence intensity. Again, the most important factor is the broadening of the excitation and emission band of VO43- with the increase of temperature, thus increase the overlapping part of the two bands and increase the energy transfer efficiency. Similarly, the absorption band of Eu is also broadaned with the increase of temperature and so increase its overlap with the emission band of VO43- and increase the efficiency of energy transfer from VO43-to Eu3+ resulting in the marked in''crease of lumineicence intensity. However, when the temperature outruns 350℃,thermal quenching begins to play a marked role in the luminescence and causes the luminescence intensity to decrease gradually.