Influence of the precursor solution chemistry on the deposition of thick coatings by spray pyrolysis

The influence of the chemistry of the precursor solution on the deposition of thick oxide coatings by air blast spray pyrolysis is reported. Coatings of four different oxide materials were deposited using aqueous lanthanum–zirconyl, yttrium–zirconyl, aluminum, and aluminum–magnesium nitrate based precursor solutions. The most suitable deposition temperature interval was determined for each selected precursor solution system and correlated to thermogravimetric analyses of the as-deposited green coatings. The quality of the green coatings was further characterized in terms of microstructure, porosity, and crack-freeness by electron microscopy. The effect of the concentration of the precursor solution on the deposition temperature interval and the microstructure of the green coatings was explained in relation to the precursor salt saturation limit. A trend was established based on the results obtained for the four systems, and guidelines for successful deposition of thick coatings by spray pyrolysis are proposed.