Achieving tunable emitting YAl3(BO3)4:Eu phosphors by substituting cations (Sr2+, Ca2+, Ga3+, In3+) and controlling BO3 group polarizability

Abstract

In order to explore the influence factor on the luminescence characteristics and valence state of Eu ions, a series of YAl₃(BO₃)_4−m(PO₄)_m:0.05Eu, Y_0.925−xAC_xL_xBO:0.05Eu, Y_0.925−yAS_yL_yBO:0.05Eu, Y_0.925−zAG_zBO:0.05Eu and Y_0.925−wAI_wBO:0.05Eu phosphors are synthesized in a CO atmosphere. It is found that the content ratio of Eu²⁺ to Eu³⁺ ions is closely related to the crystal volume. The larger the volume, the larger the polarizability of BO₃ anionic groups, and the larger the content ratio of Eu²⁺ to Eu³⁺ ions. When Y³⁺ cations in YAl₃(BO₃)₄ are replaced by Sr²⁺ or Ca²⁺ ions with a larger radius, the ratio of Eu²⁺ to Eu³⁺ ions increases, and the maximum ratio is 0.798. When Ga³⁺ ions with a radius smaller than that of Y³⁺ ions but larger than that of Al³⁺ ions are doped, Al³⁺ ions are preferentially replaced by Ga³⁺ ions, resulting in the increase of crystal volume, and the ratio of Eu²⁺ ions to Eu³⁺ ions increases from 0.159 to 0.359. When In³⁺ ions with a radius smaller than that of Y³⁺ ions but larger than that of Al³⁺ ions are added, the crystal volume decreases with increasing In³⁺ concentration, and the proportion of Eu²⁺ to Eu³⁺ ions decreases accordingly; moreover, new luminescence centers are observed, which come from oxygen vacancy defects. In short, the results indicate that the luminescence properties, especially the content ratio of Eu²⁺ to Eu³⁺, can be adjusted by regulating the matrix components, and this should be used to adjust the white emission or red–blue ratio.