Tunable photoluminescence of LiNbO3: RE3+ (RE3+ = Dy3+, Sm3+, Dy3+/Sm3+) single-phase phosphors for warm white LEDs

LiNbO3 single-phase phosphors with varying single-doping and co-doping contents of Dy3+ and Sm3+ ions were fabricated via the solid phase reaction. All the X-ray diffractions of these samples revealed that they belonged to the single-phase trigonal structure of LiNbO3. LiNbO3: Dy3+ phosphors could have a neutral white light at 392 nm excitation owing to two strong emission bands (at 488 and 585 nm). Upon the excitation of 412 nm, LiNbO3: Sm3+ phosphors produced orange-red light which attributed to the biggest emission of Sm3+ at 613 nm. The most appropriate doping content of Dy3+ and Sm3+ and the concentration quenching mechanism were also examined. The PL spectra of Dy3+ matched well with the PLE spectra of Sm3+, implying that the energy might be delivered from Dy3+ to Sm3+. At 392 nm excitation, Dy3+ and Sm3+ co-doping LiNbO3 phosphors showed tunable photoluminescence from ordinary to warm white light when doped with more Sm3+ ions. The process of Dy3+ passing on the energy to Sm3+ was validated through the PL spectra of LiNbO3: Dy3+/Sm3+ phosphors. The decay lifetimes also affirmed the energy transfer process. Moreover, Li0.97NbO3: 0.02Dy3+/0.01Sm3+ phosphors exhibited admirable thermal property with the activation energy 0.15 eV. Hence, the results strongly suggested that LiNbO3: Dy3+/Sm3+ phosphors could be applied to fabricate warm white LEDs.