The present invention proposes a device for the vapour-phase deposition of chemical species onto support grains of spherical or similar shapes placed in a fluidized bed, comprising: • a first fluidized-bed chamber (1), housed in which is a fluidization component (8), formed into a funnel, to receive support grains (2) of spherical or similar shapes, • a second chamber (3) in fluid connection with the first chamber (1), intended both to provide precursors, in vapour phase, of the chemical species to be deposited on the support grains (2) and to transport a fluidizing gas in the direction of the first chamber (1), • a flute (9), positioned at the inlet of the fluidization component (8), in order to control the distribution of the vapour-phase precursors and of the fluidizing gas within the fluidization component (8), characterized in that the distribution flute (9) comprises one or more external grooves or recesses (92), the or each groove (92) comprising a first portion oriented along the longitudinal axis of the flute (9) and a second portion that winds helically around this axis in order to generate a fluidizing gas vortex within the first chamber (1).