Electrostatic spray deposition of NiO/CGO films

Abstract

Deposition parameters were varied systematically to obtain NiO/Gd-doped CeO2 composite films using the electrostatic spray deposition method. The microstructure and morphology of the obtained films were investigated using a scanning electron microscope and an x-ray diffractometer. The degree of wetting of aerosol droplets on substrates decreased in the order of silicon wafer > stainless steel > glass. For deposition on silicon wafers, a continuous, flat layer was formed first due to excellent wetting of aerosol droplets on the substrate. Isolated particles were then nucleated and precipitated from the subsequent landing droplets and scattered on the bottom layer due to the very limited wetting of aerosol droplets on the flat oxide layer. Preferential landing of aerosol droplets on the isolated particles and subsequent precipitation and agglomeration of the fine particles finally resulted in a cauliflower morphology. Higher deposition temperature and lower flow rate of precursor solution resulted in drier droplets and hence diminished wetting and favoured particle precipitation, preferential landing of aerosol droplets and subsequent particle agglomeration. Increasing substrate roughness also favoured preferential landing of aerosol droplets and particle agglomeration. The composition of the deposited films was in fairly good agreement with that of the starting solution as revealed by the inductively coupled plasma mass spectrometer.

Fabrication of ceramic electrolytic films by the method of solution aerosol thermolysis (SAT) for solid oxide fuel cells (SOFC)

“…Although some degree of crystallization of the GSC film is evident even after heat treatment at 500°C, peaks become sharper and more intense after heat treatment at 700°C. In fact, as has been shown in the literature [39], complete crystallization takes place only above 800°C but crystalline phases are present in as-deposited films even at deposition temperatures above 350°C [40]. In addition, relative intensities of the crystallized film at 700°C follow the pattern of the literature standard for CGO10.…”

“…It can be seen that the film is of uniform thickness with no diffusion or reaction of GSC with the YSZ substrate. Spray pyrolysis can also be used for the fabrication of thin electrode films [40] onto the solid electrolyte surface and in that case EDS is used for identification of reaction or diffusion of electrode components with or into the electrolyte surface.…”

Elaboration of thin and dense CGO films adherent to YSZ by electrostatic spray deposition for IT-SOFC applications

“…The charges on the substrate surface induced in the strong electrostatic field concentrate more where the curvature is greater. 19 So the charged droplets incoming at the surface will be more attracted towards these more curved areas. This is referred to as ''preferential landing''.…”

“…These agglomerates create some irregularities of high curvature that enhance the particle agglomeration. Hwang et al 19 show that when the substrate roughness was increased, preferential landing was promoted leading to particle agglomeration. Consequently, for a temperature above 325 1C a porous microstructure is observed.…”

“…18 For a very short deposition time (few seconds), the morphology might be influenced by the nature of the substrate depending on the wetting of the droplet but if the deposition time increases, the nature of the substrate does not change the microstructure of the film. [19][20][21] Different microstructures of electrodes and electrolyte films deposited by ESD for IT-SOFCs are illustrated in ref. 22-24. They are dependent on the process parameters (nozzle-to-substrate distance, substrate temperature, solution flow rate, deposition time) and physico-chemical properties of the precursor solution (boiling point, conductivity, surface tension, viscosity.…”