Synthesis and characterization of Ca₂Sn_1-xCe_xO₄ with blue luminescence originating from Ce⁴⁺ charge transfer transition

Ce⁴⁺-doped Ca₂SnO_4 with a one-dimensional structure, which emits bright blue light, is prepared by using a solid-state reaction method. The x-ray diffraction results show that the Ce⁴⁺ ions doped in Ca_2SnO_4 occupy the Sn⁴⁺ sites. The excitation and emission spectra of Ca_2Sn_1-xCe_xO_4 appear to have broad bands with peaks at \sim 268 nm and \sim 442 nm, respectively. A long excited-state lifetime (\sim 83 \mus) for the emission from Ca_2Sn_1-xCe_xO_4 suggests that the luminescence originates from a ligand-to-metal Ce⁴⁺ charge transfer (CT). The luminescent properties of Ca_2Sn_1 - xCe_xO_4 have been compared with those of Sr_2CeO_4, which is the only material reported so far to show Ce^4 + CT luminescence. More interestingly, it is observed that the emission intensity of Ca_2Sn_1 - xCe_xO_4 with a small doping concentration (x \sim 0.03) is comparable to that of Sr_2CeO_4 in which the concentration of active centre is 100%.