Theoretical study by analytical equations of optical properties of the phosphors Zn2SnO4 codoped with Cr3+ and (Al3+ or Eu3+) via the crystal field control

The phenomenon of persistent luminescence in the phosphors Zn2SnO4 doped by Cr3+ and codoped by Al3+ or Eu3+ is related to the energy levels of the doping transition ions Cr3+ and rare earth ions Eu3+, the concentration of Al3+ substituting Zn and Sn, the intrinsic defects and the energy bands of the Zn2SnO4 matrix. To fully understand the procedure of persistent luminescence in these phosphors, we firstly determine the role of the Cr3+ ions in this process. For this reason, a crystal-field theory, using the Racah tensor algebra method, of the optical region associated to the transitions between the Stark levels of Cr3+ in these phosphors was performed. We examine then the influence by codoping with Al3+ and Eu3+ on the persistent luminescence process. In the second step, we analyze the role of the traps after discussing some of these properties. Finally, we propose an energy transfer mechanism from PLE, PL spectra and TL curves. •electronic structure Zn2SnO4:Cr3+ co-doped by Al3+-Eu3+.•Energy transfer mechanism from PLE, PL spectra, and TL is proposed.