Spray Pyrolysis
1. Introduction to Spray Pyrolysis
Spray Pyrolysis (SP) is a versatile, aerosol-based process for the synthesis of thin films, nanoparticles, and powders. It involves spraying a precursor solution onto a heated substrate (or through a hot zone), where the droplets undergo evaporation, solute precipitation, pyrolysis (thermal decomposition), and sintering to form the desired material.
Core Principle: Liquid aerosol droplets → Solvent evaporation → Solute decomposition → Solid film/particle formation via thermal energy
2. Process Schematic
3. Fundamental Stages of Spray Pyrolysis
Each droplet undergoes the following sequence:
Stage 1: Atomization
The precursor solution is converted into fine droplets (1–100 μm diameter).
Stage 2: Droplet Transport
Droplets travel toward the heated substrate through a carrier gas.
Stage 3: Solvent Evaporation
As the droplet approaches the hot zone, solvent evaporates:
Stage 4: Solute Precipitation
When solvent is completely removed, the solute precipitates:
- Volume precipitation → solid particles
- Surface precipitation → hollow/crust formation
Stage 5: Pyrolysis (Thermal Decomposition)
Precipitated precursor decomposes:
Stage 6: Sintering & Densification
The decomposed material sinters on the substrate surface, forming a continuous film.
Stage 7: Film Growth
Successive droplets impact, spread, and build up the film thickness.
4. Types of Deposition Mechanisms
Depending on substrate temperature (T_s) relative to solvent boiling point (T_b) and precursor decomposition temperature (T_d):
