Discovering new colors of luminescence in CaTiO3 with rare-earths doped through co-doping

Abstract

The luminescence of CaTiO3:Pr has been known since mid-90s [1, 2] and its persistent luminescence has been explained via InterValence Charge Transfer transitions. However, the trivalent dysprosium doped materials besides presenting white luminescence does not present any persistent luminescence. On the other hand, the expected red emission on materials doped with Eu3+ only occur when exciting in the forbidden 4f6-4f6 transitions. The objectives of this work are to show the synthesis and luminescence proprieties of CaTiO3:Dy3+ and CaTiO3:Dy3+,R3+ prepared with the sol-gel method [3, 4]. The excitation spectra of single Eu3+ or Dy3+ doped materials (Fig. left) show for Eu3+, only the 4f6-4f6 transitions while for Dy3+ both the 4f9-4f9 transitions as well as the O2-→TiIV charge transfer and the host absorption. The excitation spectrum for the Dy-Eu co-doped material monitoring the Eu3+ emission at 610 nm exhibit both the Eu3+ intraconfigurational transitions as well as the O2-→TiIV charge transfer and the host absorption. This result indicates that there is no direct energy transfer from Dy3+ to Eu3+, but Dy3+ acts as a sensitizer for Eu3+ to be excited by host transitions. Based on experimental data the energy level diagram was constructed (Fig. right) showing that Eu3+ is deep inside the valence band.