Eu 3+/2+ co-doping system induced by adjusting Al/Y ratio in Eu doped CaYAlO 4 : preparation, bond energy, site preference and 5 D 0 - 7 F 4 transition intensity.

CaY 1- x Al 1+ x O 4 :2%Eu ( x = 0, 0.1, 0.2) phosphors have been synthesized via a solid-state reaction process. XRD patterns indicate that they are pure phase. The photoluminescence properties of the CaY 1- x Al 1+ x O 4 :2%Eu phosphors exhibit both the blue emission of Eu 2+ (4f 6 5d 1 -4f 7 ) and red-orange emission of Eu 3+ ( 5 D 0 - 7 F 1,2,3,4 ) under UV light excitation, which showed that the Eu 3+/2+ co-doping system was obtained by adjusting the Al/Y ratio. Eu 3+ ions can be reduced to Eu 2+ ions when the Al/Y ratio was changed. In this work, the bond energy method was used to determine and explain the mechanism of the site occupation of Eu ions entering the host matrix. Also, the emission spectrum showed an unusual comparable intensity 5 D 0 - 7 F 4 transition peak. The relative intensity of 5 D 0 - 7 F 2 and 5 D 0 - 7 F 4 can be stabilized by changing the relative proportions of Al 3+ and Y 3+ . Furthermore, this was explained by the J-O theory.