Ce4+-Based Compounds Capable of Photoluminescence by Charge Transfer Excitation under Near-Ultraviolet–Visible Light

Ce4+-based charge transfer phosphor is not common and has been reported mainly in Sr2CeO4 with an excitation band peaking at ∼290 nm, mismatching with the near-ultraviolet light emitting diodes. Herein, we report a new series of Ce4+-based compounds Sr4.4Ce2.6REZnO12 (RE = Y, La, and Eu) capable of photoluminescence induced by O2––Ce4+ charge transfer excitation under near-ultraviolet–visible light. The crystal structure of Sr4.4Ce2.6EuZnO12 was determined by single crystal X-ray diffraction. The RE = La and Y samples were confirmed to be iso-structure compounds of the RE = Eu sample by powder X-ray diffraction. By introducing highly covalent Zn2+–O2– bonds into the framework, the Ce4+–O2– bonds are lengthened due to the effect of the Ce4+–O2––Zn2+ stretch. The lengthened Ce4+–O2– bond weakens the repulsion of the electrons between Ce4+ and O2–, thereby lowering the charge transfer energy to the visible light region. Incorporation of Eu3+ into the present compounds realized red emission under near-ultravi...