Ural Federal University, Mira Street 19, 620002 Yekaterinburg, Russia.
J Phys Condens Matter. 2011 Mar 16;23(10):105501. doi: 10.1088/0953-8984/23/10/105501. Epub 2011 Feb 18.
This research is focused on the 4f-5d transitions in Ce(3+) centers doped into tetragonal β-SrAlF(5) single crystals belonging to the I4(1)/a space group. The presence of four non-equivalent Sr(2+) sites in this compound leads to the appearance of three spectroscopically non-equivalent Ce(3+) luminescence centers, which can be well distinguished using a time-resolved laser spectroscopy technique. All 4f-5d transitions have slightly varying excitation and emission energies with characteristic probabilities resulting in several decay times that can be determined experimentally. One of these centers experiences strong perturbation due to a defect nearby, probably the O(2-) impurity ion substituting for the F(-) ion and acting as a charge compensator as well. Identification of these photoluminescence centers is performed using crystal field calculations. The crystal field parameters are calculated for two identified centers using the structural data for SrAlF(5); diagonalization of the crystal field Hamiltonian results in obtaining the splitting of the Ce(3+) 5d states. This method allows 'regular' unperturbed Ce(3+) centers with selected Sr(2+) sites to be assigned.
这项研究专注于掺杂在属于 I4(1)/a 空间群的四方β-SrAlF(5)单晶体中的 Ce(3+)中心的 4f-5d 跃迁。在该化合物中存在四个不等价的 Sr(2+)位点，导致出现三个光谱学上不等价的 Ce(3+)发光中心，这可以使用时间分辨激光光谱技术很好地区分。所有 4f-5d 跃迁的激发和发射能量略有不同，特征概率导致几个可以通过实验确定的衰减时间。其中一个中心由于附近的缺陷而受到强烈干扰，可能是 O(2-)杂质离子替代 F(-)离子，同时充当电荷补偿剂。使用晶体场计算来识别这些光致发光中心。使用 SrAlF(5)的结构数据计算了两个已识别中心的晶体场参数；晶体场哈密顿量的对角化导致 Ce(3+) 5d 态的分裂。该方法允许指定具有选定 Sr(2+)位点的“规则”未受干扰的 Ce(3+)中心。
