The effect of Eu3+ and Gd3+ co-doping on the morphology and luminescence of NaYF4:Eu3+, Gd3+ phosphors

beta-NaYF4:Eu3+ microparticles co-doped with Gd3+ ions were obtained by hydrothermal synthesis at 180 degrees C using citric acid as a stabilizing agent. All synthesized materials have a beta-NaYF4 crystalline phase, where the unit cell volume increases upon the addition of Eu3+ and Gd3+ ions. The particles have a hexagonal prism shape and a size of 40-714 nm, where Eu3+ and Gd3+ doping results in size reduction. Upon 393 nm excitation, phosphors exhibit distinct emission peaks centered at 591, 615, and 695 nm and a weak band at 650 nm attributed to D-5(0)-F-7(J) transitions (J = 1-4). The optimum Eu3+ doping concentration was found to be 30% in the NaYF4 host. Concentration quenching was realized through dipole-dipole interactions. Kinetic measurements showed a gradual decline of the D-5(0) lifetime from 6.7 ms to 2.2 ms along with an increase in Eu3+ doping concentration. Co-doping of the small Gd3+ number led to an increase of emission intensity and D-5(0) lifetime. The effects of Eu3+ doping and Gd3+ co-doping on radiative and nonradiative decay rates were studied using 4f-4f intensity theory.

Automated summary

beta-NaYF4:Eu3+ microparticles co-doped with Gd3+ ions were successfully synthesized using a hydrothermal method, showing specific emission peaks and shape characteristics. The effects of Eu3+ and Gd3+ doping concentrations on emission intensity and lifetime were thoroughly studied, providing a theoretical basis for optimizing the luminescent properties of the material.