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.