Luminescência e estrutura dos nano cristais de LaF3:Ln3+ (Ln3+ = 5%Tb3+ ou 5%Eu3+): mistura de estado solido para obtenção de luz ajustável por cor no verde-vermelho

Abstract

Nanocrystals co-dated with the Tb3+ and Eu3+ ions have been of interest to many researchers for obtaining color-adjustable light from yellowish green to red-orange and for obtaining white light-emitting diodes in recent years. In these systems, the energy transfer between Tb3+ as an activator and Eu3+ as a sensitizer is exploited for the development of functional optical materials. In this work, the host, the LaF3 nanocrystal, is doped with 5% Tb3+ or 5% Eu3+ and heat-treated at 500°C for 3h [2] and mixed in proportions ranging from 15 to 85% of the rare earth. The mixtures were excited at 377 nm and their emissions spectra were investigated bymainly considering the emission bands at 548 nm of Tb3+ and 596 nm of Eu3+ which could be used to generate the adjustable light in the green to red spectral region which showed an excellent potential for emissions in this spectrum band with no evidence of radiative energy transfer and with transitions in levels. Moreover, the structures of the nanoparticles were investigated to confirm their monophasic crystalline nature and the effectiveness of the thermal treatment and it was found the formation of a nano particles with an average size of 15 nm and a surface free of pores and roughness. The lifetimes of the excited state were also measured for the proposed mixed systems, which remained with values between 53 to ≈ 93 µs for the 548 nm emission of Tb3+ and from ≈ 19 to ≈ 28 µs for the 596 nm emission of Eu3+, in order to investigate possible energy transfers between two rare earth species and to understand how this could affect the generation of color-adjustable light.