Synthesis and optical properties of novel red-emitting phosphors Ba3Lu1–xEuxB9O18 (x = 0–0.85)

Abstract

The novel red-emitting phosphors Ba3Lu1–xEuxB9O18 (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.85) belonging to the Ba3REEB9O18 (REE – Y, Pr–Lu) family were successfully obtained by a multistep solid-phase synthesis. X-ray diffraction experiments revealed no phase transitions caused by the Eu3+ → Lu3+ isomorphic substitution in this series of solid solutions. An increase in the Eu3+ content leads to an expectable increase of hexagonal unit cell parameters and volume. Optical properties of the Ba3Lu1–xEuxB9O18 (x = 0–0.85) phosphors were investigated. The highest emission intensity was demonstrated by Ba3Lu0.6Eu0.4B9O18. The concentration quenching of luminescence was revealed for the x(Eu3+) > 0.4 samples. Concentration quenching, quantum yield and structural data were compared between three red-emitting Ba–Lu borates-phosphors (BLBO:Eu3+) containing independent crystallographic sites for the REE ions (n = 1–3) in crystal structure. It was revealed that the higher the number of nonequivalent cationic REE sites suitable for the Eu3+ → Lu3+ substitution, the higher the quantum yield taking into account practically equal amount of an optimal concentration of the activator-ion. Such an observation could be useful for a crystal chemical design of novel phosphors.