Study on the properties of Sm3+-Doped CaTbAl3O7 phosphors

New single phase and adjustable emission phosphors have attracted a lot of attention because of the good luminous properties. In this work, Sm3+ doped CaTbAl3O7 phosphors are prepared in air by solid-state method. The crystal structure, concentration dependent spectra, lifetimes, and luminescence properties are investigated. Because of the 4f(8) -> 4f(7)5d(1) and 4f -> 4f transitions of Tb3+ ion, host (CaTbAl3O7) shows an excitation spectrum in the range of 220-520 nm under monitored at 544 nm and emits yellow-green light under excitation 248, 284, and 368 nm due to the D-5(4) -> F-7(J) (J = 0, 1, 2, 3, 4, 5, and 6) transitions of Tb3+ ion. CaTbAl3O7:Sm3+ under monitored 598 nm contains the excitation spectral peaks of both CaTbAl3O7 and Sm3+ ion. With excitation at 368 nm, CaTbAl3O7:Sm3+ glows orange-red light, its PL spectrum has both host (CaTbAl3O7) and Sm3+ ion contributing, and the chromaticity coordinates are about (0.5499, 0.4351). Under excitation 402 nm, the red-orange emission of CaTbAl3O7:Sm3+ is only the contribution of Sm3+ ion and the chromaticity coordinates are about (0.5823, 0.4168). The energy transfer process from Tb3+ in host (CaTbAl3O7) to Sm3+ ions can be confirmed via the spectral properties. We explain the luminous mechanism of CaTbAl3O7:Sm3+ by the energy level diagrams of Tb3+ and Sm3+.