Dutczak D, Jüstel T, Ronda C, Meijerink A
Department of Chemical Engineering, Münster University of Applied Sciences, Stegerwaldstr. 39, D-48565 Steinfurt, Germany.
Phys Chem Chem Phys. 2015 Jun 21;17(23):15236-49. doi: 10.1039/c5cp01095k.
The luminescence properties of Eu(2+) doped strontium aluminates are reported and reviewed for a variety of aluminates, viz. SrAl12O19, SrAl4O7, Sr4Al14O25, SrAl2O4 and Sr3Al2O6. The aim of the research is to investigate the role of local coordination and covalency of the aluminate host lattice, related to the Sr/Al ratio, on the optical properties of the Eu(2+) ion. The UV and VUV excited luminescence spectra as well as luminescence decay curves were recorded to characterize the luminescence properties of the investigated aluminates. The emission of Eu(2+) ions varies over a wide spectral range, from ultraviolet (UV) to red, for the series of aluminates. The variation in emission color can be related to the crystal-field splitting of the 5d levels and the covalent interaction with the surrounding oxygen anions. In the least covalent material, viz. SrAl12O19:Eu(2+), narrow line emission due to the (6)P7/2-(8)S7/2 transition occurs at 4 K, indicating that the 4f(6)5d excited state is situated above the (6)P7/2(4f(7)) excited state around 360 nm. The most alkaline material, viz. Sr3Al2O6:Eu(2+) is the most covalent host and exhibits several d-f emission bands in the yellow to red spectral range due to the Eu(2+) ions located on different crystallographic Sr(2+) sites. The Eu(2+) emission spectra in the other aluminates confirm the trend that with increasing Sr/Al ratio the Eu(2+) emission shifts to longer wavelengths. Interesting differences are observed for the Eu(2+) from different crystallographic sites which cannot always be related with apparent differences in the first oxygen coordination sphere. The discussion gives insight into how in a similar class of materials, strontium aluminates, the emission color of Eu(2+) can be tuned over a wide spectral region.
本文报道并综述了 Eu(2+) 掺杂铝酸锶的发光特性，涉及多种铝酸盐，即 SrAl12O19、SrAl4O7、Sr4Al14O25、SrAl2O4 和 Sr3Al2O6。该研究的目的是探究与 Sr/Al 比相关的铝酸锶主体晶格的局部配位和共价性对 Eu(2+) 离子光学性质的作用。记录了紫外和真空紫外激发的发光光谱以及发光衰减曲线，以表征所研究铝酸盐的发光特性。对于该系列铝酸盐，Eu(2+) 离子的发射在从紫外到红色的宽光谱范围内变化。发射颜色的变化可能与 5d 能级的晶体场分裂以及与周围氧阴离子的共价相互作用有关。在共价性最低的材料 SrAl12O19:Eu(2+) 中，由于 (6)P7/2-(8)S7/2 跃迁导致的窄线发射在 4 K 时出现，表明 4f(6)5d 激发态位于约 360 nm 处的 (6)P7/2(4f(7)) 激发态之上。碱性最强的材料 Sr3Al2O6:Eu(2+) 是共价性最强的主体，由于位于不同晶体学 Sr(2+) 位点上的 Eu(2+) 离子，在黄色到红色光谱范围内呈现出多个 d-f 发射带。其他铝酸盐中的 Eu(2+) 发射光谱证实了随着 Sr/Al 比增加，Eu(2+) 发射向更长波长移动的趋势。对于来自不同晶体学位点的 Eu(2+)，观察到了有趣的差异，这些差异并不总是与第一氧配位球中的明显差异相关。该讨论深入探讨了在类似的一类材料铝酸锶中，如何在宽光谱区域内调节 Eu(2+) 的发射颜色。
