Effect of structure, particle size and relative concentration of Eu3+ and Tb3+ ions on the luminescence properties of Eu3+ co-doped Y2O3:Tb nanoparticles

Eu3+ co-doped Y2O3:Tb nanoparticles were prepared by the combustion method and characterized for their structural and luminescence properties as a function of annealing temperatures and relative concentration of Eu3+ and Tb3+ ions. For Y2O3:Eu,Tb nanoparticles annealed at 600 and 1200 deg. C, variation in the relative intensity of excitation transitions between the 7F6 ground state and low spin and high spin 4f75d1 excited states of Tb3+ is explained due to the combined effect of distortion around Y3+/Tb3+ in YO6/TbO6 polyhedra and the size of the nanoparticles. Increase in relative intensity of the 285 nm peak (spin-allowed transition denoted as peak B) with respect to the 310 nm peak (spin-forbidden transition denoted as peak A) with decrease of Tb3+ concentration in the Y2O3:Eu,Tb nanoparticles heated at 1200 deg. C is explained based on two competing effects, namely energy transfer from Tb3+ to Eu3+ ions and quenching among the Tb3+ ions. Back energy transfer from Tb3+ to Eu3+ in these nanoparticles is found to be very poor