Don't you have any standard reference that you could follow the methodology? Maybe you could adapt some methodology and perform yours.

Regards.

I have collected information from many references, but none seem to go into detail into the amounts required or the yield of the processing for this purpose

There are different sol-gel methods you can use. You don't necessarily need urea. For your dopants, I'd try a curve with 0.3, 0.5, 0.7, 1, 2, and 3 mol % in the aqueous solvent that you use for your synthesis and select the one with the best properties for your application. This will at least give you a starting point.