Enhanced afterglow behavior of a new Eu2+: NaBa4(BO3)3 yellow phosphor co-doped with different cations Dy3+, Ho3+and Nd3+

A new Eu²⁺: NaBa₄(BO₃)₃ phosphor, synthesized under conventional solid state approach, exhibits bright yellow persistent luminescence with the co-doping of Eu²⁺, Ln³⁺ (Ln = Dy³⁺, Ho³⁺, Nd³⁺). XRD investigation reveals that all samples are pure phase phosphors with cubic structure, indicating the doped Eu²⁺and Ln³⁺ cations were incorporated into the lattice that did not form inclusive phase in the material. Since there are two coordination forms ([EuO6] and [EuO8]) of Eu²⁺ cations in the matrix, the above yellow luminescence can be divided into two different emissions centering at 558 nm and 627 nm, confirming the crystallographic environment on the photoluminescence from Eu²⁺ center. Optimal doping concentrations for each cations were further determined as 2% atm for Eu²⁺, 2% atm for Dy³⁺, 3% atm for Ho³⁺ and 2% atm for Nd³⁺. Afterglow behaviors are also observed for samples with Ln³⁺ co-doping, which reveal typical double exponential decay model. Among the phosphors synthesized, the sample 2 at%Eu²⁺/3 at%Ho³⁺: NaBa₄(BO₃)₃ displays the best performance with higher initial brightness and longer lifetime, which can be attributed to the formation of electron traps with high concentration and suitable energy level, as confirmed by the result from thermal stimulated luminescence (TSL) analysis.