On the Nature of the Luminescence of Sr[sub 2]CeO[sub 4]

Recently efficient blue‐white luminescence from Sr 2 CeO 4 was reported. The emission was assigned to a ligand‐to‐metal charge‐ transfer transition of Ce 4 + . Charge transfer (CT) emission from Ce 4 + , or any other tetravalent lanthanide, had not been reported previously. Here, further research on the luminescence of Sr 2 CeO 4 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 Ce 4 + ‐ O 2 − CT transition. Second, lifetime measurements are discussed. The life‐ time, 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 Sr 2 CeO 4 as a phosphor in lighting.