Formation and stabilization of tetragonal phase in sol–gel derived ZrO2 treated with base-hot-water

Zirconia (ZrO2) nanoparticles have been prepared by sol–gel route. Low temperature crystallization using base-hot-water treatment (BHWT) was conducted for the sol–gel derived ZrO2 gel powders at 90 °C and at pH 14 for various periods of time. Single phase nanocrystalline tetragonal ZrO2 (t-ZrO2) was successfully obtained by immersing the dry gel powders into hot, basic condition water and kept at rest for given time. BHWT at pH 14 with sodium hydroxide (NaOH) medium by digestion for 12 h and then continuing with stirring for 12 h resulted in the formation of t-ZrO2 with surface area of 292 m2/g and crystal size of 7 nm. Study on base solution medium, using NaOH, shows that the sodium ions play an important role for the formation of t-ZrO2 by incorporating into the crystal structure during the treatment. BHWT also effectively removed organic groups of the sol–gel derived ZrO2 nanoparticles.