The luminescence regulation effect of Na+ on the Yb3+/Er3+ co-doped Y2O3 up-conversion films

Abstract

Na+-Er3+/Yb3+ co-doped Y2O3 up-conversion films were prepared using a sol-gel method and spin-coating; the field emission scanning electron microscopy (FE-SEM), energy dispersive spectrometry (EDS) data, X-ray diffraction (XRD) patterns, Raman spectra, Fourier transform infrared spectroscopy (FT-IR) data and photoluminescence (PL) spectra were collected to characterize these films. The results show that the up-conversion (UC) films are composed of 100-nm nano-particles that are evenly distributed, well crystallized and have a high transmittance. After Na+ ion doping, the Y2O3 lattice maintained its original basic structure, while the Na+ ions slightly magnified the lattice, reducing the lattice symmetry and creating surface defects. All the samples had green emission at 535 nm and red emission at 660 nm when exited with a 980-nm laser. For lower doping levels, Na+ ion doping suppressed the green emission with the intensity reduced to 1/8 of the original, while it reduced the red emission only a little. As the doping concentration further increased, the red emission improved and then declined again. In other words, Na+ ion doping regulated the up-conversion luminescence spectra to some extent. The Na+ ions were a positive controller in 535 nm emission and effectively shielded the green emission by its own polarity around 535 nm. The Na+ ions also impacted the process of the energy transfer via simultaneously changing the phonon energy, the lattice symmetry and the surface defects.