Luminescence properties, tunable emission and energy transfer of Ca9MgLi(PO4)7:Bi3+/Eu3+ phosphor

Bi3+, Eu3+ singly doped and Bi3+/Eu3+ co-doped Ca9MgLi(PO)(7) (CMLPO) with a single pure phase are synthesized in air by high-temperature solid-state method and their crystal structure and the luminescence properties are investigated. CMLPO:Bi3+ with excitation at 313 nm shows blue emission. CMLPO:Eu3+ with excitation at 318 and 394 nm emits red emission. CMLPO:Eu3+, Bi3+ with excitation at 318 nm shows an adjustable color emission when the ratio between Eu3+ and Bi3+ ions is changed. CMLPO:Eu3+, Bi3+ under excitation 394 nm only emits a single red color light. The optimal Eu3+ concentration in CMLPO:Eu3+ and Bi3+ concentration in CMLPO:8 mol%Eu3+, Bi3+ are similar to 8 mol% and 2 mol%, respectively. The luminescence intensity of CMLPO:Eu3+ can be enhanced 1.4-2.2 times when Bi3+ ion as sensitizer is co-doped into CMLPO:Eu3+. The energy transfer process in CMLPO:Eu3+, Bi3+ is observed and analyzed. The luminous mechanisms of samples are explained by using the energy level diagrams of Eu3+ and Bi3+ ions. The research in this paper offers effective guidance for the optical property improvement of phosphors by co-doping other ions as sensitizer.