Luminescent properties and energy transfer of orange-emitting phosphor Ca10Na(PO4)7: Eu2+, Mn2+ for NUV LEDs

• Energy transfer from Eu2+ to Mn2+ in Ca10Na(PO4)7 was carefully studied.
• The absorption of phosphor in NUV region can be enhanced with Eu2+/Mn2+ co-doped.
• Emission color can be tuned from yellow to reddish-orange.

Color-tunable Ca10Na(PO4)7: Eu2+, Mn2+ phosphors were firstly synthesized via high-temperature solid-state method. At 350 nm NUV excitation, Ca10Na(PO4)7: Eu2+, Mn2+ emits a broad yellow band and a intense red band, which nearly covers the entire visible region. The mechanism of Eu2+ ⟶ Mn2+ energy transfer is found to be a quadrupole–quadrupole interaction, and the corresponding critical transfer distance is calculated as 8.24 Å. Emission color of Ca10Na(PO4)7: Eu2+, Mn2+ can be easily modulated from yellow to reddish-orange by adjusting the Mn2+ content. Results indicated that Ca10Na(PO4)7: Eu2+, Mn2+ might be promising for NUV LED application as an orange-emitting phosphor.

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