Auto-combustion synthesis of Sm3+-doped NaYF4 phosphors: Concentration quenching, optical transition and luminescent properties

Abstract

A series of NaYF4:Sm3+ phosphors with various Sm3+ concentrations were prepared via an auto-combustion-assisted fluorination method. By the use of X-ray diffraction (XRD), we investigated the phosphors' crystal structure, and pure phase NaYF4:Sm3+ were confirmed. Irregular and agglomerated hexagonal-like particles were observed in FE-SEM images of the phosphors. Moreover, higher magnification TEM images have been collected. Based on fluorescence spectra, the concentration quenching and luminescence thermal stability of NaYF4:Sm3+ phosphors were studied. On the basis of Van Uitert's model, the electric dipole-dipole interaction was proven to be the mechanism for energy transfer between Sm3+ ions. Furthermore, the temperature-dependent fluorescence was investigated in depth, and it was shown that the Arrhenius model-based crossover process can adequately describe the temperature-dependent thermal quenching behavior of 4G5/2 level for Sm3+ in NaYF4 powders. Finally, based on the diffuse-diffraction spectrum and the fluorescence decay curve, the optical transition properties of Sm3+ in the examined NaYF4 phosphors were analyzed in the framework of Judd-Ofelt theory.