Eu^2＋掺杂CaSi2O2N2荧光粉发光性能

Luminescence Properties of Eu^(2+)-doped CaSi_2O_2N_2 Phosphors

采用固相反应法合成了组成为Ca1-xEuxS i2O2N2的Eu2+掺杂CaS i2O2N2荧光粉。通过荧光光谱对样品的发光性能进行了研究,发现Eu2+掺杂CaS i2O2N2荧光粉发射光谱为宽波段的单峰结构,主要包含绿光和黄光区,发射峰在556~568 nm。从发射光谱的宽带特征来看,CaS i2O2N2∶Eu2+的发射主要对应着Eu2+离子4 f65d→4 f7跃迁。从激发光谱所覆盖的范围还可以看到,样品可以有效的被UV蓝-光激发,这意味着该类荧光粉在白光LED方面有可能得到广泛的应用。另外,样品的发光性能与激发离子的浓度有着很大关系。激发离子浓度增大时,发射光谱会发生明显红移。利用这一性质,可以通过改变Eu2+浓度来调节荧光粉的发光范围,从而满足不同场合的需要。同时,Eu2+浓度提高,样品发射光谱的强度也会随之增强,在x=0.06时发射强度达到最大值,之后继续增加Eu2+浓度,强度不仅没有增加反而降低,即出现浓度猝灭现象。

Eu^2＋ -doped CaS2O2 N2 （ Ca1-xEuxSi2O2N2 ） has been prepared by solid-state reaction method, and the optical properties of the alkaline-earth silicon-oxynitride phosphor have been investigated. Eu^2＋ -doped CaSi2O2N2 displayed a single broad emission band peaking at 556 - 568 nm depending on the europium concentration. The emission bands in the spectra of Eu^2＋ -doped CaSi2O2 N2 were assigned to the allowed transition of Eu^2＋ from the lowest crystal field component of 4f^65d to 4f^7 ground-state level. It has been demonstrated that the Eu^2＋ -doped CaSi2O2N2 phosphor absorbs strongly the UV-blue part of the electromagnetic spectrum which makes this material attractive as the conversion phosphor for white light-emitting diodes （LEDs） applications. We have also shown that the optical properties depend greatly on the Eu^2＋ concentration. A systematic red shift of the emission band is observed as the Eu^2＋ concentration increases. The results indicate the photoluminescence properties can be tailored by controlling the Eu^2＋ concentration. Moreover, for all samples, starting at low Eu^2＋ concentration, the emission intensity rises to a maximum at a Eu^2＋ concentration of x = 0. 06 and falls again when the Eu^2＋ concentration continues to increase. This decrease in emission intensity beyond a critical concentration can be explained by concentration quenching, which is mainly caused by the energy transfer between Eu^2＋ ions.