Site‐selective occupation and luminescence property investigation of Ca18Na3Y(PO4)14:Eu2+ phosphor for full‐spectrum LED

Abstract

AbstractCyan‐emitting phosphors have attracted widespread attention as an integral part to realize full‐spectrum lighting. Understanding the site occupation of luminescence centers is of great importance to design and clarify the luminescent mechanism for new cyan‐emitting phosphors. Here, we report a cyan‐emitting phosphor Ca18Na3Y(PO4)14:Eu2+ synthesized by the high‐temperature solid‐state method. The crystal structure is characterized by X‐ray diffraction and refined by the Rietveld method. The diffuse reflectance spectra, excitation/emission spectra, fluorescence decay curves, thermal stability, and related mechanism are systematically studied. The results show that Ca18Na3Y(PO4)14:Eu2+ crystallizes in a trigonal crystal system with space group R3c. Under excitation at 350 nm, a broadband cyan emission can be obtained at 500 nm with a half‐width of about 120 nm, which is caused by Eu2+ occupying five different sites in host, namely, Na2O12 (450 nm), (Ca3/Na1)O8 (485 nm), Ca2O8 (515 nm), Ca1O7 (565 nm), and (Ca4/Y)O6 (640 nm), respectively. Moreover, crystal structure, room and low temperature spectroscopy, and luminescence decay time are used to skillfully verify the site‐selective occupation of Eu2+. Finally, a full‐spectrum light‐emitting diode (LED) lamp is fabricated with an improved color rendering index (∼90.3), CCT (∼5492 K), and CIE coordinates (0.332, 0.318). The results show that Ca18Na3Y(PO4)14:Eu2+ has the potential to act as a cyan emission phosphor for full‐spectrum white LEDs.