Abstract

Recently efficient blue-white luminescence from Sr2<>CeO4 _{was reported. The emission was assigned to a ligand-to-metal charge-transfer transition of Ce4+<>. Charge transfer (CT) emission from Ce4+^{, or any other tetravalent lanthanide, had not been reported previously. Here, further research on the luminescence of Sr2<>CeO4 is reported. Three topics are discussed. First the nature of the luminescence is investigated. The results provide evidence that the efficient blue-white emission is not related to a lattice defect and support the assignment of the emission to a Ce4+<>-O2- CT transition. Second, lifetime measurements are discussed. The lifetime, 65±5 µs at 6 K, is long for a parity allowed CT transition. The spin-forbidden nature of the emission can explain the observed lifetime. Finally, the temperature dependence of the emission intensity and luminescence lifetime is investigated. At 300 K both the emission intensity and the lifetime are reduced to about 50% of the values at 6 K. This shows that the quantum efficiency measured to be about 40% at room temperature is close to the maximum efficiency at room temperature. The low quenching temperature is a serious drawback for application of Sr2<>CeO4 as a phosphor in lighting.(Author abstract)}}