SrB4O7：Pr3+,Mn2+中的Pr→Mn能量传递

从能量传递的角度出发,利用同步辐射光源(德国HASYLAB实验室的SUPERLUMI实验站)对Pr³⁺和Mn²⁺掺杂的SrB₄O₇粉末样品进行了光谱研究.206nm激发下,在SrB₄O₇:Pr³⁺(0.1%,摩尔分数)样品中观察到了来自Pr³⁺离子1S0能级的光子级联发射.SrB₄O₇:Pr³⁺样品的发射谱与SrB₄O₇:Mn²⁺样品监测Mn²⁺离子640nm发射的激发谱在330~430nm的波长范围里存在显著的光谱重叠.这个光谱重叠有利于Pr³⁺→Mn²⁺的能量传递发生,从而将Pr³⁺离子级联发射中第一步不实用的紫外或近紫外光子转换为Mn²⁺的红光发射.双掺杂样品SrB₄O₇:Pr³⁺,Mn²⁺与单掺杂样品SrB₄O₇:Pr³⁺的发射谱比较揭示出Pr³⁺→Mn²⁺的能量传递的确存在,并且提供了一种传递效率的估算方法,表明通过“Pr³⁺-Mn²⁺”组合有可能获得量子效率大于1的高效真空紫外激发发光材料.

Pr→Mn Energy Transfer in SrB4O7:Pr,Mn

The luminescence of Pr³⁺ or Mn²⁺ singly doped as well as Pr³⁺ and Mn²⁺ codoped SrB₄O₇ powder microcrystalline samples were investigated using synchrotron radiation.The photon cascade emission originating from the ¹S₀ level was observed in the SrB₄O₇:Pr³⁺(0.1%,mol fraction)sample upon 206 nm excitation.There are desirable spectral overlaps in the region of 330⁴30 nm between the emission spectra of the SrB₄O₇:Pr³⁺ sample and the excitation spectra of the SrB₄O₇:Mn²⁺ sample monitoring the Mn²⁺ luminescence at 640 nm.The wavelengths corresponding to transitions ¹S₀→¹I₆,³P_2,1,0(405 nm)and ¹S₀→¹D₂(340 nm)of Pr³⁺ coincide very well with those corresponding to transitions ⁶A_1g→⁴E_g-⁴A_1g(410 nm)and ⁶A_1g→⁴T_2g(350 nm)of Mn²⁺,respectively.These spectral overlaps are in favor of the energy transfer from Pr³⁺ to Mn²⁺,converting the first step photon from Pr³⁺:¹S₀ in the unpractical ultraviolet or near-ultraviolet regions into the red Mn²⁺ emission.A comparison of the room temperature emission spectra of the SrB₄O₇:Pr³⁺,Mn²⁺ sample with that of the SrB₄O₇:Pr³⁺ sample revealed the existence of the proposed energy transfer between Pr³⁺ and Mn²⁺.This conclusion about Pr→Mn energy transfer was also supported by the evidences from the low temperature(10 K)spectra and decay curves of 405 nm emission from Pr³⁺ singly doped and Pr³⁺,Mn²⁺ codoped samples.The efficiency of the energy transfer was estimated to be 43% by a simple equation based on the comparison of the emission spectra of the SrB₄O₇:Pr³⁺,Mn²⁺ sample with that of the SrB₄O₇:Pr³⁺ sample,thus a 143% quantum efficiency was achieved,suggesting an promising VUV phosphor based on Pr³⁺ and Mn²⁺ combination.