Crystal structure, optical spectroscopy and energy transfer properties in NaZnPO(4):Ce(3+), Tb(3+) phosphors for UV-based LEDs

A new series of Ce(3+), Tb(3+) singly doped and Ce(3+)/Tb(3+) co-doped NaZnPO(4) (NZPO) phosphors have been synthesized via a high-temperature solid-state reaction method at 800 °C. The crystal cell structure, luminescence proprieties, energy transfer, and chromaticity coordinates of the as-prepared phosphors were investigated in detail. The photoluminescence spectra of NZPO:Ce(3+) phosphors exhibited broad emission in the 300–380 nm range, while under UV excitation, the singly doped NZPO:Tb(3+) phosphor showed emission peaks at ∼485–690 nm among which the green emission peak appears at ∼543 nm. The Tb(3+) green emission was significantly enhanced almost 20 times via energy transfer from Ce(3+) to Tb(3+). The energy transfer (ET) mechanism from Ce(3+) to Tb(3+) in NZPO is identified to be a resonant type via the dipole–dipole interaction mechanism with an ET efficiency of 91%. Intense green emission is obtained at very low Tb(3+) concentrations under 285 nm excitation, making NZPO:Ce(3+)/Tb(3+) an efficient UV-excited green phosphor. The NaZnPO(4):Ce(3+)/Tb(3+) phosphors are promising UV convertible materials of green light for UV -LEDs applications.