Böhnisch David, Baur Florian, Jüstel Thomas
Department of Chemical Engineering, Münster University of Applied Sciences, Stegerwaldstrasse 39, 48565 Steinfurt, Germany.
Dalton Trans. 2018 Jan 30;47(5):1520-1529. doi: 10.1039/c7dt04151a.
This work concerns the polycrystalline red emitting solid state compound LiBa(TbEu)(MoO), from which a series of powder samples was prepared by a conventional solid-state reaction. The phase formation of the samples was investigated by X-ray diffraction which revealed the formation of a solid solution without a miscibility gap. Photoluminescence (PL) spectra and decay curves were recorded as a function of Tb and Eu concentration and temperature. It turned out that the external quantum efficiency of Eu photoluminescence is between 30 and 80%, while the highest quantum yield is achieved for about 60% Tb. An increase of emission intensity can be realized by co-doping of Eu and Tb. Moreover, the emission has a luminous efficacy of 275 lm W which is a distinct advantage over the widely applied Mn activated fluorides. The time dependent photoluminescence as a function of Tb concentration demonstrates the presence of an efficient energy transfer from Tb to Eu. Temperature dependent PL measurements revealed that LiBa(TbEu)(MoO) loses just 20% of PL efficiency up to 400 K. Therefore, the investigated phosphors are attractive for application in pcLEDs. It is finally demonstrated that the application of a Eu/Tb co-doped ceramic disc is useful for the colour conversion of a blue emitting LED with a higher conversion rate compared to LiBa(LaEu)(MoO).
这项工作涉及多晶红色发光固态化合物LiBa(TbEu)(MoO)₄，通过传统的固态反应制备了一系列粉末样品。通过X射线衍射研究了样品的相形成，结果表明形成了没有混溶间隙的固溶体。记录了光致发光（PL）光谱和衰减曲线作为Tb和Eu浓度以及温度的函数。结果表明，Eu光致发光的外量子效率在30%至80%之间，而当Tb含量约为60%时可实现最高量子产率。通过Eu和Tb的共掺杂可以实现发射强度的增加。此外，该发射的发光效率为275 lm/W，这相对于广泛应用的Mn激活氟化物具有明显优势。随时间变化的光致发光作为Tb浓度的函数表明存在从Tb到Eu的有效能量转移。温度依赖的PL测量表明，LiBa(TbEu)(MoO)₄在高达400 K时PL效率仅损失20%。因此，所研究的磷光体对于在pcLED中应用具有吸引力。最终证明，与LiBa(LaEu)(MoO)₄相比，Eu/Tb共掺杂陶瓷盘的应用对于蓝色发光LED的颜色转换是有用的，且具有更高的转换率。
