Clusters modification for tunable photoluminescence in Nd3+:SrF2 crystal

• 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 Nd 3+ clusters in SrF 2 crystal. The results show that structures of the clusters vary greatly and it depends on the ionic radius of rare-earth La 3+ , Nd 3+ , Gd 3+ and Y 3+ . The cubic sublattice centers are stable in large size rare-earth La 3+ - and Nd 3+ -doped SrF 2 , and the square antiprism centers are more stable in smaller size Gd 3+ - and Y 3+ -doped crystals. It suggests that the square antiprism clusters become more stable with decreasing ionic radius in going from La 3+ , Nd 3+ , Gd 3+ to Y 3+ , while the cubic sublattice centers become unstable. Based on the results, the mixed [Nd 3+ -La 3+ ] and [Nd 3+ -Gd 3+ ] clusters are also calculated. Stability of square antiprism clusters is improved with increasing concentration of Gd 3+ in [Nd 3+ -Gd 3+ ] clusters, and that weakened when codoped with La 3+ . 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 Nd 3+ :SrF 2 modified by La 3+ , Gd 3+ and Y 3+ . The varied cluster structures provide us a methodology towards designing of new rare-earth-doped fluoride materials.