Investigation of Yb3+/Er3+ doped SrGd2O4 up-conversion nanomaterial obtained via combustion synthesis

Abstract

Nanopowders of a new up-conversion materials, SrGd 2 O4 co-doped with different Yb3+ (1, 2.5 and 5 at%) and constant Er 3+ (0.5 at%) concentrations were prepared by combustion method. X-ray powder diffraction (XRPD) showed that nanoparticles have orthorhombic structure (Pnma), assigned to the JCPDS Card No:01-072-6387. Rietveld refinement indicated a decrease in the size of the unit cell, lattice parameters, and cell volume, due to successful doping of Yb3+ and Er 3+ ions into the host structure. Transmission electron microscopy (TEM) revealed that obtained nanostructure is composed of agglomerated nanoparticles, while energy dispersive spectroscopy (EDS) confirmed uniform distribution of all constituting elements in them. Up-conversion (UC) luminescence spectra measured in function of laser pumping power indicated that two-photon UC process is established in nanoparticles as a result of the trivalent erbium f-f electronic transitions: two green emission bands at 523 and 551 nm ( 2 H11/2 , 4 S 3/2 → 4 I 15/2) as well as a red emission band at 661 nm ( 4 F9/2 → 4 I 15/2). The rise of Yb3+ concentration from 1 to 5 at% provokes a significant change of the green to red ratio showing the ability to fine-tuning the color output.