Complete B-site cation regulation accomplish UV-excited red phosphors in double perovskite oxides

Abstract

As a widely explored red luminescent center, Eu3+ can reflect the features of the occupied lattice structure. Eu3+ ions energy levels and splitting in different hosts are mainly constrained by spin-orbit coupling and crystal field effects. This work reports an all-B-substituted perovskite-type red phosphor, and the role of the above two effects in this system is investigated by replacing Li+ (B1) and W6+ (B2) in BaLaLiWO6 with Na+ and Mo6+, respectively. Each sample's XRD and refinement results show that the all-B-site substitution does not affect the space group type; it only has a certain change in the unit cell parameters. The introduction of sodium ion makes the lattice expansion significantly enhance the intensity of the charge transfer band in the UV region. The introduction of Mo6+ significantly undermines the luminescence performance due to the influence of spin-orbit coupling. Subsequently, the symmetry changes of the position occupied by Eu3+ were verified by the red-orange ratio of Eu3+. The quantum yield of BaLaLi0·4Na0·6WO6: 0.30Eu3+ red phosphor under near ultraviolet excitation reaches 49.6%. Warm white light emission of color coordinates (0.363, 0.365) can be achieved by packaging with near UV chips, and the color rendering index can reach 83.3, which means that the phosphor has certain application prospects in WLED.