Luminescence properties of NaSrPO4: Tm3+ as novel blue emitting phosphors with high color purity

Tm3+-doped NaSrPO4 phosphors were synthesized through solid-state sintering. Their crystal structure, micro-morphology, luminescent performance, fluorescent lifetime, and chromaticity property were studied. The synthesized NaSr1-xPO4: xTm3+ phosphors show an intense excitation peak at 357 nm near ultraviolet (NUV), and exhibit two blue emission peaks at 452 and 476 nm, corresponding to the transitions of 1D2 → 3F4 and 1G4 → 3H6 of Tm3+, respectively. Optimized doping concentration of Tm3+ in NaSr1-xPO4: xTm3+ is determined to be 0.02, while concentration quenching at higher Tm3+ doping concentrations is associated with the dipole-dipole interaction of Tm3+. The phosphor owns blue emission property with Commission International De L'Eclairage (i.e., CIE) chromaticity coordinate of (0.153, 0.043) and high color purity of 95%. All in all, the NaSrPO4: Tm3+ phosphors are a new kind of potential blue emitting phosphors for NUV white light-emitting diodes.