Clusters modification for tunable photoluminescence in Nd3+:SrF2 crystal

• Published in: Journal of alloys and compounds 2022-04, Vol.899, p.162913, Article 162913
• Main Authors: Ma, Fengkai, Zhou, Haiqiong, Tang, Qinyu, Su, Liangbi, Zhang, Mingjie, Zhang, Peixiong, Yin, Hao, Li, Zhen, Lv, Qitao, Chen, Zhenqiang
• Format: Article
• Language: English
• Subjects: Clusters; Crystal structure; Doped crystals; Emission spectra; First principles; Gadolinium; Low temperature; Mathematical analysis; Metal ions; Modified clusters; Photoluminescence; Rare earth elements; Rare-earth-doped fluorite crystal; Strontium fluorides; Tunable photoluminescence
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2021.162913

•Characters of the mixed clusters depend on that of the ingredient rare-earth ions.•The neodymium clusters could be modified variably.•The photoluminescence was tunable with the codopants. In the work, the first principles calculation and low temperature spectra were utilized to investigate the modification on Nd3+ clusters in SrF2 crystal. The results show that structures of the clusters vary greatly and it depends on the ionic radius of rare-earth La3+, Nd3+, Gd3+ and Y3+. The cubic sublattice centers are stable in large size rare-earth La3+- and Nd3+-doped SrF2, and the square antiprism centers are more stable in smaller size Gd3+- and Y3+-doped crystals. It suggests that the square antiprism clusters become more stable with decreasing ionic radius in going from La3+, Nd3+, Gd3+ to Y3+, while the cubic sublattice centers become unstable. Based on the results, the mixed [Nd3+-La3+] and [Nd3+-Gd3+] clusters are also calculated. Stability of square antiprism clusters is improved with increasing concentration of Gd3+ in [Nd3+-Gd3+] clusters, and that weakened when codoped with La3+. The results reveal that characteristics of the mixed centers depend on species and contents of the ingredient rare-earth ions. Local environment of the active ions could therefore be modified by codoping the other rare-earth ions, which agreed well with the tunable absorption and emission spectra of Nd3+:SrF2 modified by La3+, Gd3+ and Y3+. The varied cluster structures provide us a methodology towards designing of new rare-earth-doped fluoride materials.