Synthesis and characterization of nanophase yttria co-doped with erbium and ytterbium

Nanophase yttria particles, co-doped with erbium and ytterbium, have been synthesized via gas-phase condensation with CO2-laser heating. The as-prepared nanoparticles were about 2 nm in diameter and mostly amorphous. Annealed nanoparticles were about 20–40 nm in diameter and showed good crystallinity. The annealed nanoparticles showed the characteristic near-infrared as well as green and red upconversion luminescence from the erbium ions.