Synthesis and visible down- and up-conversion emissions from Yb3+/Ho3+/ Tm3+ Co-Doped Y4Al2O9 (YAM) nanocrystalline particles

Abstract

We studied Yb3+/Ho3+/Tm3+ co-doped Y4Al2O9 (YAM) crystalline phase prepared by a modified polymeric precursor method, involving pyrolytic treatment and a calcination at 1100 ◦C during 3 h. X-ray powder diffraction patterns and high-resolution transmission electron microscopy images revealed the formation of single monoclinic crystalline phase. The co-doped YAM phase presents an optical bandgap of 4.58 eV and high diffuse reflectance value in the visible region. Down- and up-conversions were observed and analyzed. Photoluminescence measurements showed three emission bands in the visible region: 471–486 nm (blue region), 536–548 nm (green region), and 638–665 (red region) from Tm3+ and Ho3+ ions. The CIE color coordinates of the up-conversion emissions under excitation at 980 nm were determined, demonstrating a yellowish emission color. Finally, the lifetimes of some Ho3+ and Tm3+ levels were determined, and an energy mechanism transfer is suggested for up-conversion processes.