g 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 †

Yu Pan, Wenjun Wang, Yuhan Zhu, Haibing Xu, Liqun Zhou, Hyeon Mi Noh, Jung Hyun Jeong, *b Xiaoguang Liu* and Ling Li *a CaY1 xAl1+xO4:2%Eu (x 1⁄4 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 xAl1+xO4:2%Eu phosphors exhibit both the blue emission of Eu 2+ (4f5d–4f) and red-orange emission of Eu (D0– F1,2,3,4) under UV light excitation, which showed that the Eu 3+/2+ co-doping system was obtained by adjusting the Al/Y ratio. Eu ions can be reduced to Eu 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 D0– F4 transition peak. The relative intensity of D0– F2 and D0– F4 can be stabilized by changing the relative proportions of Al 3+ and Y. Furthermore, this was explained by the J–O theory.