Synthesis and Luminescence Properties of Clew-Like CaMoO\u3csub\u3e4\u3c/sub\u3e:Sm\u3csup\u3e3+\u3c/sup\u3e, Eu\u3csup\u3e3+\u3c/sup\u3e

Eu3+ and Sm3+ co-doped CaMoO4 microclews have been successfully synthesized via a facile hydrothermal method directly in surfactant-free environment. The as-prepared phosphor present clew-like agglomerates composed of 40 nm nanosheets under the moderated reaction temperature. The red phosphor CaMoO4:Eu3+, Sm3+ can generate a strong absorption line at 405 nm, originating from6H5/2 → 6P5/2 transition of Sm3+, which is suitable for the emission of the near-ultraviolet light-emitting diodes (∼400 nm). Energy transfer between Sm3+ and Eu3+ is detected from the varied photoluminescence spectra with different Eu3+ concentrations and the energy transfer mechanism is clarified via the photoluminescence spectra. When Sm3+ is excited (405 nm), the electron is excited from 6H5/2 to 6P5/2, and then relaxed to 4G5/2. It jumps from 4G5/2 to the lower levels corresponding to the emissions of Sm3+; meanwhile, the transfers from 4G5/2 state of Sm3+ ion to 5D0 state of Eu3+ ion come out. The transition of5D1 → 7FJ (J = 0, 1, 2) does not appear indicating that the transfer from 4G5/2 state of Sm3+ to 5D0 state rather than 5D1 state of Eu3+ is the energy transfer pathway