Salt smoke: The formation of submicron sized RbCl particles by thermal evaporation in 0.5–100 Torr of argon and helium

We have shown that it is possible to form submicron‐sized particles of a highly ionic compound RbCl by thermally evaporating the reagent salt in 0.5–100 Torr of inert gas. By collecting the particles on a surface and then carefully removing them, bulk powder can be collected. The ambient gas species, pressure, system geometry, and evaporation temperature profile affect the size and geometry of the particles which form. Evidence indicates that if strong convection currents are present during evaporation, the number of individual primary particles in the powder is increased and the number of sintered strings of primary particles is reduced. The primary particle size depends on the geometry of the evaporation source used and is independent of the ambient pressure. In argon, the size of the particles collected is independent of the distance between the collection plates and the source. In helium, the size of the primary particles collected from a single run can vary from ∼10 to 1000 nm; the particle size collected is strongly dependent on the distance of the collection plates from the evaporation source.