Effect of Ce dopant ions on the shape and luminescence of YPO:Eu and YPO:Tb nanocrystals.

Nanoparticles of YPO:Eu, YPO:Eu:Ce, YPO:Tb, and YPO:Ce:Tb with different amount of Eu or Tb dopant ions were synthesized by a hydrothermal route. Particle structures and morphologies were investigated and it was found that the increase of Eu or Tb ions, and co-doping with Ce ions resulted in a transition of the crystal structure from tetragonal to hexagonal phase. The phase transition and the morphology transformation should be ascribed to the change of the average radius of cation by doping Ce, or to the changing the amount of Eu or Tb. The energy transfer from Ce ions to Eu and Tb ions was tested by studying the photoluminescence lifetime of YPO:Eu, YPO:Eu:Ce, YPO:Tb, and YPO:Ce:Tb nanoparticles, and their energy transfer results in the improvement of the luminescence intensity. A schematic diagram for the electronic transitions of the studied systems is presented. [ABSTRACT FROM AUTHOR]