Tunable up-conversion luminescence from Er3+/Tm3+/Yb3+ tri-doped Sr2CeO4 phosphors

Er3+/Tm3+/Yb3+ tri-doped Sr2CeO4 phosphors have been synthesized via high-energy deformation processes. The structure of the synthesized phosphor is identified to be a pure orthorhombic structure. By varying the concentration of dopant ions (Er3+, Tm3+, Yb3+), the obtained phosphors present tunable up-conversion emissions under 975 nm a laser diode excitation. The white up-conversion light emitted from a 3 mol%Er3+/1 mol%Tm3+/10 mol%Yb3+ ions tri-doped Sr2CeO4 phosphor was observed corresponding to the transitions from 1G4→3H6 (Tm3+), 1G4→3F4 (Tm3+), 2H11/2→4I15/2 (Er3+), 4S3/2→4I15/2 (Er3+) and 4F9/2→4I15/2 (Er3+) transitions at 478, 652, 526, 552 and 664 nm, respectively. The efficient up-conversion emission is attributed to energy transfer between Yb3+ and Er3+ or Tm3+ ions. Moreover, there is a chance for an energy transfer from the 4I15/2 level of the Er3+ to the 3H5 level of the Tm3+ to enhance the blue emission. The results indicate that the synthesized phosphors can be potentially applied to many devices, such as optical displays, lighting sources for light emitting diodes and lasers.