Eu^(2+),Cr^(3+)共掺杂SrAl_(12)O_(19)发光体的发光性质及能量传递

Luminescent Properties and Energy Transfer in SrAl_(12)O_(19)∶Eu^(2+),Cr^(3+)

采用高温固相法制备了Eu2+,Cr3+单掺杂及共掺杂的SrAl12O19发光体,研究了它的发光性质和能量传递动力学过程。Eu2+的5d→4f发射峰位于400 nm,与Cr3+位于350~450 nm波长范围的4A2→4T1的吸收带有显著的光谱重叠,有利于Eu2+→Cr3+的能量传递发生,从而将来自于Eu2+离子的紫光转换为Cr3+的深红光发射。在共掺杂的样品中,当激发Eu2+时观察到Cr3+离子的2E→4A2红色线谱发射。当监测该红色线谱发射时,激发光谱中包含有Eu2+的吸收,证明了在SrAl12O19体系中Eu2+→Cr3+能量传递的存在。能量传递导致Eu2+的荧光寿命随Cr3+浓度的增加而缩短,计算表明能量传递效率随Cr3+浓度增加而提高,当Cr3+浓度为5%时能量传递效率可达到50%。

There exists an increasing demand for red emitting phosphors to be used in color display and illumination.SrAl12O19∶Eu2＋ has attracted much attention for its excellent properties such as high quantum efficiency and good stability.However,the emission of SrAl12O19∶Eu2＋ peaks at 400 nm,which is hard to be used in display and illumination.As we know,Cr3＋ with red emission lines is one of the most used activators for solid state laser and other luminescent materials.Therefore,we have studied the emission and excitation spectra as well as energy transfer in SrAl12O19∶Eu2＋,Cr3＋.The Cr3＋,Eu2＋ singly doped and co-doped samples were synthesized by solid-state reaction at 1 400 ℃.The emission band of Eu2＋ peaked at 400 nm is originating from the 5d-4f transition,which has large spectral overlaps with the 4A2→4T1 Absorption band of Cr3＋ covering between 350 nm and 450 nm in the ultraviolet-blue region.It means the possibility of energy transfer from Eu2＋ to Cr3＋.The conversion of violet-blue emission to the red may be obtained by the energy transfer.In the co-doped samples,the emission band of Eu2＋ appears in the range of excitation spectra of Cr3＋ emission,which indicates the occurrence of energy transfer from Eu2＋ to Cr3＋.In order to explain energy transfer further,the lifetime of Eu2＋ emission in SrAl12O19∶1%Eu2＋,x%Cr3＋（x=0,0.2,1.0,2.0,3.0,4.0,5.0） has been measured.It shows that the lifetime of Eu2＋ reduces following increasing Cr3＋ concentration due to the energy transfer from Eu2＋ to Cr3＋.The energy transfer efficiency as a function of Cr3＋ concentration has been calculated using the measured fluorescent lifetimes of Eu2＋,indicating the transfer efficiency increases with increasing Cr3＋ concentration,and may reach 50% as Cr3＋ concentration is 0.05.