1. Sol-gel process chemistry

The sol-gel process is a so-called "soft chemistry" method for obtaining ceramics by simple polymerization of molecular precursors in solution [14][15] . These precursors can be inorganic salts (Al(NO ₃ ) ₃ , for example), but are most often transition metal or silicon alkoxides of the general formula M(OR) ₄ with M = Si, Ti, Zr...

The formation of an oxide network from alkoxides involves the hydrolysis and condensation reactions described in figure