VUV spectroscopic properties of rare-earth (RE=Eu, Tb and Dy)-doped A2Zr(PO4)2 (A=Li, Na and K) phosphates

This study fully investigated the vacuum ultraviolet excitation spectra of pure and rare-earth (RE=Eu, Tb and Dy)-doped A(2)Zr(PO4)(2) (A=Li, Na and K) phosphors. The synthesized Na and Li compounds were characterized by XRD showing two new types of phases after indexation. Although these three pure compounds had different crystal structures, they exhibited similar luminescence properties. For Eu3+ -activated samples, the broad excitation band centered at 217 nm could be attributed to the CT transition between O2- (2p(6)) and Eu3+ ions. For Tb3+ -doped samples, two groups of f-d transitions were observed, where a strong broad band at 221 nm was due to the spin-allowed f-d transition. Energy transfer from O2- to Dy3+ was not observed in Dy3+ -doped phosphors, probably because it overlapped considerably with the CT transition from O2- to Zr4+ at 187 nm.