Synthesis and luminescence of Eu²⁺-doped alkaline-earth apatites for application in white LED

A series of Eu²⁺-doped alkaline-earth apatites (alkaline-earth=Ca, Sr and Ba) were synthesized by a solid state reaction method with excess chlorides, and the effect of the used excess chlorides on the luminescent property of the synthesized products was discussed. Photoluminescence measurements showed that Eu²⁺-doped calcium apatite exhibited intensely blue wide-band emission peaking at 457 nm under near UV excitation among the Eu²⁺-doped Ca, Sr and Ba apatites. Blue and white LEDs were successfully fabricated by pre-coating the calcium apatite phosphors onto ∼395 nm-emitting InGaN chips. The CIE coordinates, color temperature, luminous efficacy and rendering index value of the fabricated white LED are (0.3432, 0.3234), 4969 K, 8 lm/W and 80, respectively. The results indicate that the Eu²⁺-activated calcium apatite phosphor is a promising candidate as a blue component for fabrication of near UV-based white LEDs.