# Improvement of the thermal stability of hydrous zirconia by post-synthesis treatment with NaOH and NH4OH solutions

I read a paper about how researchers improved the thermal stability of hydrous zirconia by post-synthesis treatment with $$\ce{NaOH}$$ and $$\ce{NH4OH}$$.[1]

While the surface area of non-treated zirconia though more, but after calcinations at high temperatures the % decrease of the treated zirconias was very less as compared to non treated zirconia. Is there any reason for this observation besides the changes the changes in pore volume and size? Any specific reason for the morphology obtained?

G. Aguila, S. Guerrero, F. Gracia, P. Araya, Appl. Cat. A: General 2006, 305 (2), 219-232. DOI: 10.1016/j.apcata.2006.03.025

• Surface area is heavily dependent on pore size. This is a general trend that when you calcine something, its surface area decreases. I think both NaOH or ammonium hydroxide promote formation of surface -OH groups and when you heat it high temperature it helps in maintaining the pore structure. Check what the paper says about pore sizes. A lot of work is done on silica and you might get a clue. – M. Farooq Feb 27 '19 at 22:27
• i think it will have something to do with surface hydroxylation densities ,and stabilization of alumina surface by stabilizing agents. – Omkar Kedge Mar 1 '19 at 4:30