Photoluminescence Properties and Energy Transfer of ${\hbox{Eu}}^{3+}$ , ${\hbox{Bi}}^{3+}$ Co-Doped ${\hbox{Ca}}_{9} {\hbox{Y}}({\hbox{PO}}_{4})_{7}$ Phosphors

Bi
³⁺
and Eu
³⁺
ions co-activated Ca
₉
Y(PO
₄
)
₇
phosphors were prepared by solid-state reaction. The crystal structure, luminescence properties, and morphology of these phosphors were studied. X-ray diffraction results showed that when the calcination temperature was 1100
^°
C, the phosphates could obtain their own pure phase. Scanning electron microscopy images exhibited that the average particle diameter of the phosphors was approximately 5-8 μm. The phosphors could be excited by near-UV light at 397 nm, which agrees with the current UV chip, and with red light emission at 617 nm. The co-doped Bi
³⁺
ions demonstrated efficient energy transfer to Eu
³⁺
ions, and the emission intensity of Bi
³⁺
and Eu
³⁺
co-doped samples were approximately two times as high as that of Eu
³⁺
singly doped samples. The CIE value (0.64, 0.34) of Ca
₉
Y
_0.92
(PO4)7: Bi
³⁺
_0.01
, Eu
³⁺
_0.07
was close to the standard red color coordinates. All results indicated that the red phosphors could be potentially applied to white light-emitting diodes.