I am trying to coat a film of Barium and Zirconium precursors over a glass but I get this type of circles (see picture attached), and the film does not seems to be uniform.
Organic reactant/product or precursor decomposition product with slow scope for escape, I guess. What are the precursors and processing routes are required to be known for further prediction. Also surface condition involving hydrophobicity/hydrophilicity and cleanliness might play a role
We often see two inputs to non-uniform thin films that look just like that.
The less common is, if it is a polymer, that the polymer "likes" the solvent too much. Oligomers in general will be very mobile in a good solvent. If the oligomer "likes" the solvent more than the glass surface or other type of substrate, it will migrate. My suggestion would be to find a solvent (or blend of 2 or more solvents) that the silicate, polymer or oligomer is barely soluble in, so the reaction is biased to the glass. That could also help open up their operating window on drying times and volatility.
The more common is that there is water or other contamination in the coating. We see many times that a customer will spray a coating using a method that uses compressed gas, and that the compressed gas is contaminated with either particles or with water.
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