Laser-driven gas-phase synthesis of nanodispersed multicomponent oxides for catalytic applications
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Laser-driven gas-phase synthesis provides a powerful route for producing functional oxide nanoparticles with controlled physicochemical properties. However, the formation of multicomponent oxide nanoparticles is strongly affected by differences in the evaporation behavior of the constituent oxides. In this work, we investigate Al 2 O 3 -Cr, ZrO 2 -Cr, and SiO 2 -Fe systems as model examples representing three characteristic cases: the effective evaporation temperature of the oxide additive is higher than, close to, or lower than that of the matrix oxide. The nanoparticles were synthesized by laser evaporation of ceramic targets followed by vapor condensation in a controlled argon atmosphere. TEM, HRTEM, HAADF-STEM, EDX mapping, X-ray diffraction, X-ray fluorescence analysis, and BET measurements were used to characterize their morphology, phase composition, elemental distribution, and specific surface area. The results show that the relative evaporation temperatures of the matrix and dopant oxides determine the evaporation sequence, vapor-phase composition, condensation pathway, and ultimately the dopant distribution in the resulting nanoparticles. When the evaporation temperatures are close, homogeneous dopant incorporation is favored, as observed for ZrO 2 -Cr. In contrast, a large evaporation temperature mismatch leads to sequential evaporation and the formation of composite structures with locally enriched dopant regions, as demonstrated for Al 2 O 3 -Cr and SiO 2 -Fe. These findings establish a simple criterion for predicting the structure of multicomponent oxide nanoparticles produced by laser gas-phase synthesis and provide a basis for the rational design of catalysts and catalyst supports.
