Photoluminescence and energy transfer properties of a novel molybdate KBaY(MoO4)3:Ln3+ (Ln3+ = Tb3+, Eu3+, Sm3+, Tb3+/Eu3+, Tb3+/Sm3+) as a multi-color emitting phosphor for UV w-LEDs

Abstract

In this article, we report the preparation and luminescence properties of a series of novel rare-earth doped KBaY(MoO₄)₃ phosphors. The XRD patterns for the as-prepared samples have been assigned to the pure KBaY(MoO₄)₃ phase. The Tb³⁺, Eu³⁺ and Sm³⁺ singly-doped phosphors all show good luminescence properties with their characteristic excitations and emissions. We have optimized the rare-earth ion doping concentrations, yielding the compositions KBaY_0.60(MoO₄):0.40Tb³⁺, KBaY_0.50(MoO₄):0.50Eu³⁺ and KBaY_0.96(MoO₄):0.04Sm³⁺ with corresponding quantum yields of 15.80% (λ_ex = 376 nm), 40.67% (λ_ex = 392 nm) and 16.79% (λ_ex = 402 nm), respectively. In addition, we have chosen co-doping of Tb³⁺/Eu³⁺ and Tb³⁺/Sm³⁺ into the host to realize tunable emission colors. We have observed energy transfer from Tb³⁺ to Eu³⁺ and from Tb³⁺ to Sm³⁺ ions in the as-prepared samples, which resulted in tunable emission colors from green to red and to orange-red under UV excitation, respectively. Moreover, investigation of the excitation and emission spectra, and decay lifetimes with increasing doping concentrations confirmed efficient energy transfer from Tb³⁺ to Eu³⁺ and from Tb³⁺ to Sm³⁺ ions in the co-doped samples. We also analyzed the energy transfer mechanisms between Tb³⁺ and Eu³⁺ and between Tb³⁺ and Sm³⁺ and both were determined to be dipole–dipole interactions. These results show that the as-prepared materials could serve as candidate phosphors for use in UV-pumped w-LEDs.