VUV excited luminescence of europium activated calcium borophosphate prepared in air

Abstract

XAFS (EXAFS and XANES) at Eu–L 3 edge were used to determine the local structure and the valences of europium in CaBPO 5:Eu prepared in air. The results of EXAFS showed that the doped europium atoms were nine-coordinated by oxygen atoms and the distances of bond Eu–O were 2.39 Å in the host lattice. XANES at Eu–L 3 edge exhibited that Eu 2+ and Eu 3+ coexisted in the matrix. The luminescent spectrum of the material excited by VUV at 147 nm presented a similar spectrum with that excited by f–f transition of Eu 3+ at 396 nm and f–d transition of Eu 2+ at 312 nm. The broad emission band due to both 4f 65d – 4f 7 transition of Eu 2+ and f – f transition of Eu 3+ could be observed in emission spectra, which indicated that the trivalent europium ions were reduced in air in the matrix at high temperature by the defects [V Ca]″ formed by aliovalent substitution between Ca 2+ and Eu 3+ ions. The UV excitation spectrum showed the typical f–f transition of Eu 3+ and f–d transition of Eu 2+. The bands with the maxima at about 113 and 158 nm in VUV excitation spectrum were assigned to originate from the absorption of the host lattice.