Structural and photoluminescence properties of doped and REE-endmember mixed-framework rare-earth sorosilicates

Photoluminescence (PL) properties of lanthanide-doped mixed-framework barium yttrium sorosilicates Ln:BaY2(Si3O10) (Ln=Pr3+, Sm3+, or Er3+) and Ln:BaY4(Si2O7)(Si3O10) (Ln=Pr3+, Sm3+, Er3+, or Ho3+), and selected REE-endmembers BaREE2(Si3O10) (REE=Y, Dy) and BaREE4(Si2O7)(Si3O10) (REE=Y, Er, Ho) are presented. These silicates were synthesized by a high-temperature, molybdate-based flux-growth method. Results from single-crystal structure refinements are given and briefly discussed in the spectroscopic context. Sm3+, present in both sorosilicate structure types, causes transitions in the visible yellow to orange spectral range at 600 and 570 nm, according to the 4G5/2→6HJ transitions. Pr3+ is responsible for dominant PL bands around 500 nm due to the 3P0→3H4 transition, showing a blue-green emitting color. Er3+ exhibits green-yellow emission with strongest bands between 540 and 570 nm, which can be associated with the 4S3/2→4I15/2 transition. Ho3+ shows a dominant characteristic PL emission in the red spectral region, which is assigned to the 5F5→5I8 transition. The photoluminescence of emission of Dy3+ centers, with the main emission at 575 nm in the visible yellow region, is assigned to the 4F9/2→6H13/2 transition. Strong differences in the intensity of PL emissions of the REE-endmembers and Ln-doped silicates are caused by self-quenching effects due to high concentration of Ln3+ cations in the crystal structure. Unexpected PL emission spectra of the host sorosilicates BaY2(Si3O10) and BaY4(Si2O7)(Si3O10) are caused by trace impurity contents of other Ln3+ cations.