Energy transfer and tunable photoluminescence of novel white-emitting Sr8MgY(PO4)7: Ce3+/Eu2+/Sm3+ phosphors

To develop a novel type of white-light-emitting phosphor, we successfully prepared a series of Ce³⁺/Eu²⁺/Sm³⁺ activated color-tunable phosphor Sr₈MgY(PO₄)₇ (SMYP) through a classical solid-state reaction and crystal structure, luminescent characteristic, energy transfer and systematically investigated thermal stability of as-synthesized samples. The results manifest that the phase purity of Ce³⁺/Eu²⁺/Sm³⁺ co-doped SMYP phosphors was verified by the Rietveld structure refinements. Under 315 nm ultraviolet (UV) excitation, the Ce³⁺ single-doped SMYP phosphor reveals a broad and strong bluish-violet emission band in the range of 325–480 nm. The outstanding enhancement of Eu²⁺ emission intensity is realized by Ce³⁺ induced resonance energy transfer (ET). The ET mechanism of Ce³⁺→Eu²⁺ is governed by an electronic quadrupole-quadrupole interaction with a high ET efficiency of 89.8 %. In addition, the luminescent color of SMYP: Ce³⁺/Eu²⁺ samples can be changed from light green to white by introducing activators Sm³⁺ ions. The optimal chromaticity coordinate could be adjusted to (0.311, 0.343), which is the closest to the ideal white light coordinate (0.330, 0.330). To achieve white light, a white LED device fabricated by combining a 310 nm chip with the SMYP: Ce³⁺/Eu²⁺/Sm³⁺ phosphor shows a high color rendering index (CRI = 87.2) along with a low correlated color temperature (CCT≈4056.7 K) under the stimulation of 5 V voltage and 100 mA current. The above results show that SMYP: Ce³⁺/Eu²⁺/Sm³⁺ as a single component phosphor has potential application prospects in UV-pumped full-spectrum white LEDs.