A device for vapor deposition of chemical species on support grains of spherical or similar shape disposed in a fluidized bed. The device includes a first chamber including a fluidized bed in which a funnel-shaped fluidizer element is housed to receive support grains of spherical or similar shape; a second chamber in fluid flow connection with the first chamber to deliver precursors in a vapor phase of chemical species to be deposited on the support grains and to convey a fluidizing gas towards the first chamber; and a flute at an inlet to the fluidizer element to control distribution of the vapor phase precursors and the fluidizing gas within the fluidizer element. The distributor flute includes one or more outer grooves, each groove including a first portion oriented along the longitudinal axis of the flute and a second portion winding helically around the axis to generate a fluidizing gas vortex within the first chamber.