Eu3+/2+ co-doping system induced by adjusting Al/Y ratio in Eu doped CaYAlO4: preparation, bond energy, site preference and 5D0–7F4 transition intensity

CaY1-x Al1+x O4:2%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 CaY1-x Al1+x O4:2%Eu phosphors exhibit both the blue emission of Eu2+ (4f65d1-4f7) and red-orange emission of Eu3+ (5D0-7F1,2,3,4) under UV light excitation, which showed that the Eu3+/2+ co-doping system was obtained by adjusting the Al/Y ratio. Eu3+ ions can be reduced to Eu2+ 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 5D0-7F4 transition peak. The relative intensity of 5D0-7F2 and 5D0-7F4 can be stabilized by changing the relative proportions of Al3+ and Y3+. Furthermore, this was explained by the J-O theory.