Laser synthesis of nanopowders based on zinc selenide for the preparation of highly transparent ceramics

We report the synthesis of weakly agglomerated ZnSe and Cu:ZnSe nanopowders by evaporation of a target of a corresponding chemical composition using an ytterbium-doped fibre laser emitting periodic radiation pulses with a power of 600 W and a duration of 120 μs. Nanoparticles have the form of polyhedrons and, more rarely, of spheres with an average size of 18 nm. The productivity of nanopowder synthesis at an average laser radiation power of 300 W is ∼100 g·h^–1. Calculations show that laser radiation scattering in the original target with a porosity of ∼30 % leads to a very nonuniform distribution of radiation inside the target. In some regions of a near-surface layer of a 10–15-μm-thick target, radiation is randomly concentrated, and its intensity, due to a high refractive index of ZnSe (n ≈ 2.48), can exceed that of the incident radiation by 10-–245 times. This fact greatly facilitates optical destruction and further evaporation of the target at a low intensity of the incident radiation (∼0.43 MW/cm²). Photographing the laser plume shows that the target evaporation using periodic laser pulses makes it possible, under certain conditions, to significantly reduce the spread of melt drops. To this end, at peak radiation intensities of 0.21 and 0.46 MW/cm², the pulse durations should not exceed 400 and 200 μs, respectively.