Color-tunable emission by cation substitution in Ba_3−ySr_yY₄O₉:Bi³⁺ and sites occupation preference

A series of Ba₃Y₄O₉:Bi³⁺ phosphors with trigonal lattice in the R3 (146) space group are investigated in the aspect of structure and luminescence. The Ba₃Y₄O₉:Bi³⁺ phosphor exhibits a promising broad yellowish-green emission peaking at 524 nm at the excitation of 347 nm. When Sr²⁺ ions are introduced into series of samples, the abnormal two-peak emission behavior centered at 412 nm and 524 nm can be observed, simultaneously. Eventually, tunable emission colors are obtained from yellowish-green to blue via controlling the ratio of Sr²⁺/Ba²⁺ content. Through calculation, the corresponding environmental factor of every Y³⁺ and Ba²⁺ site can be obtained. Analysis suggests that two components of the excitation band at 344 and 361 nm are ascribed to Bi³⁺ ions which occupies Y(2)/Y(4) and Ba(1)/Ba(2), respectively. It can be further expected that the anomalous emission of 412 nm is attributed to Bi³⁺ ions which occupies Sr(1)/Sr(2) sites when substitution occurs.