XAFS at RE-L3 edge and VUV spectra of some rare earth doped borates and borophosphates

The coordination numbers of the samarium atoms and the bond distances of Sm-O in luminescent materials SrB4O7:Sm were determined by EXAFS at Sm-L3 edge. It was found that the samarium atoms are nine-coordinated by oxygen atoms and the bond distances of Sm-O are 2.40 Angstrom in the material. The fact that the coordination numbers of samarium atoms in SrB4O7:Sm was consistent with that of strontium atoms in SrB4O7, indicated the samarium atoms entered the sites of substituted strontium atoms in SrB4O7:Sm. The valences of europium in SrBPO5:Eu prepared in air were checked by means of XANES at Eu-L3 edge. It was discovered that the divalent and trivalent europium coexisted in the matrix. The results implied that the trivalent europium ions were reduced in air in the matrix at high temperature by the defects [VSr]formed by aliovalent substitution between Sr2+ and Eu3+ ions. The VUV excitation and VUV-excited emission spectra of Gd7BP2O17:Tb were measured. It was noticed that the host lattice exhibited absorption bands in VUV range and the material represented a prominent 5D4-7F5 transition with the maximum at 546 nm in emission spectrum. The results showed that Gd7BP2O17:Tb was a potential VUV-excited green luminescent material