Effect of pulses from a high-power ytterbium fiber laser on a material with a nonuniform refractive index. II. Production and parameters of Nd:Y$_2$O$_3$ nanopowders

The laser ablation of the Nd:Y$_2$O$_3$ target with substantially nonuniform refractive index leads to the formation of a needle-shaped surface with a needle height of 6–8 mm. An increase in the displacement velocity of the laser beam on the surface to 80 cm/s and an increase in the diameter of the laser spot at the central part of the beam waist to 430 $\mu$m lead to a more uniform relief of the target surface and an increase in the nanopowder yield and production rate to 22% and 23 g/h, respectively. In addition, an excess of the mole content of the low-melting Nd$_2$O$_3$ in the powder decreases from 174 to 11% in comparison with the target. At an air pressure in the evaporation chamber of 0.8 bar, the mean sizes of nanoparticles (13–14 nm) are virtually independent of the displacement velocity of the beam on the surface (7–81 cm/s) and the rate of air flow above the target (13–70 m/s) in spite of significantly different nanopowder production rates.