Densification and phase transition of Yb-doped Lu2O3 nanoparticles synthesized by laser ablation

In this work we report on the effects induced by calcining monoclinic ytterbium-doped lutetium oxide (Yb: Lu2O3) nanoparticles on their phase transformation and densification behavior. Morphology and phase evolution of powder synthesized by laser ablation were studied by scanning electron microscopy and high temperature X-ray diffraction, respectively. The powder consisted of soft agglomerates comprising 15-25 nm spherical particles with monoclinic crystal structure. The beginning of phase transformation depends on the particle packing density, resulting in the temperatures of 700 °C and 1000 °C for loose and pressed powder, respectively. Transformation-assisted vacuum sintering of as-synthesized powder at 1780 °C for 20 h resulted in a core-shell and porous microstructure of Yb: Lu2O3 ceramic due to significant density decrease and obstructed densification during phase conversion. On the other hand, transparent Yb: Lu2O3 ceramic exhibiting an optical transmittance of 76.6% at the wavelength of 1080 nm was obtained using additional calcining of powder.