Ceramic Powder Synthesis by Spray Pyrolysis

TLDR

Spray pyrolysis techniques can directly produce ceramic powders, offering flexibility for advanced powders and films, but production rates are limited by the need for sub‑5‑µm droplets and avoidance of droplet coagulation. This review examines how process parameters control particle morphology and composition in spray pyrolysis and stresses the need for improved controls, atomization, and system design to enable commercialization. A model coupling solute diffusion within droplets and solvent evaporation identifies the critical parameters that govern solid particle formation. The model shows that high‑solubility solutes and a large supersaturation gap, combined with avoidance of solvent boiling, yield solid particles, and that adjusting precursor, solution, and process parameters can produce mixed metal oxide, non‑oxide, and composite particles in solid, hollow, porous, or fibrous forms.

Abstract

A variety of spray pyrolysis (SP) techniques have been developed to directly produce ceramic powders from solutions. This paper reviews the current status of these processes in terms of the process parameters that enable the formation of particles with controlled morphology and composition. A model incorporating solute diffusion in the droplet and solvent evaporation from the droplet surface is presented to establish the critical parameters leading to solid particle formation. The model illustrates that solid particles can be obtained if solutes with high solubility and a large difference between the critical supersaturation and equilibrium concentration are used and if the process is designed to avoid solvent boiling. It is demonstrated that mixed metal oxide, non‐oxide, and composite particles that are solid, hollow, porous, or fibrous can be produced by modifying the precursor characteristics, solution properties, and process parameters. The physical and chemical flexibility of SP processes offers numerous opportunities for the controlled synthesis of advanced ceramic powders and films. However, production rates are limited by the need to produce < 5‐μm‐diameter droplets and to avoid subsequent droplet coagulation. Developments in process controls, atomization, and system design are required for wider commercialization of SP‐type processes.