Fabrication of Thin Functional Films by Solution Aerosol Thermolysis (SAT)

Abstract

The technique of air-pressurized solution spray pyrolysis was used to fabricate thin films of La 0.75 Sr 0.25 MnO 3 (LSM) and CuO-CeO 2 on dense YSZ substrates. These films are widely used in several applications such as high temperature ceramic electrochemical cells, membranes and sensors. The technique was tailored to produce films with differing morphologies and thicknesses in terms of applied substrate deposition temperatures. The droplet drying and decomposition kinetics is discussed as a function of substrate temperature, given the other processing parameters (i.e. nozzle to substrate distance, solution flow rate, air pressure/air flow rate and deposition time) constant. A graph-map is drawn containing morphology and quality of fabricated films in terms of substrate temperatures and concentration levels for this particular set of precursor salts in aqueous solutions. Within the deposition temperature range examined, film thicknesses were found to decrease with increasing substrate temperature along with a concomitant change in quality from irregular texture to smoother and of more uniform thickness. A maximum deposition temperature of about 280 • C was identified for 0.025M concentration for both types of films which correlates quite well with the Leidenfrost point measured in the literature for solvents with boiling point less than 150 • C.

Fabrication and Characterization of Functional Ceramic Films by Solution Spray Pyrolysis: Correlations with the Thermal Decomposition Characteristics of the Constituent Salts

“…This temperature is well above the dehydration temperatures of both La and Mn salts and at the onset of their final decomposition steps towards their respective oxides. In this case, due to the higher concentrations and the resulting thicker films, cracking is observed at the upper layers of the film due to non-uniform drying rates along the film thickness as mentioned by Krestou et al (9). Cracking at high concentrations, can be avoided by either reducing deposition times or increasing deposition temperatures in order to achieve similar solvent evaporation rates throughout the film's thickness.…”

“…The solution spray pyrolysis (SSP) technique is a molecular deposition method (8) that involves spraying of solution of metal salts onto a heated substrate (9). It is robust, easily up scalable and with easily controllable processing parameters, factors contributing to low fabrication costs (6).…”