Synthesis and characterization of tetragonal / monoclinic mixed phases nanozirconia powders.

Mixed phases nanozirconia was synthesized using the sol-gel process in different basic pH. Calcination was performed at 700 °C for 1 and 2 h. The synthesis process and characterization of the nanoparticles were studied by TGA, DTA, FTIR, XRD, FE-SEM and UV–visible. The presence of stable monoclinic and meta-stable tetragonal phases was confirmed by X-ray diffraction patterns for synthesized powders. As pH increased, the amount of tetragonal phase and crystallite size is increased and decreased, respectively. Also, due to the increase of calcination time, the amount of tetragonal phase and crystallite size increased. Micrographs confirmed that the particle shape is semi-spherical after calcination. Moreover, the size of zirconia nanoparticles decreased to 29.8 and 32.9%, as pH increased from 8 to 10 for samples with 1 and 2 h calcination time, respectively. The lowest particle size, 19.3 nm, is related to the sample that was synthesized at pH 10 and calcined at 700 °C for 1 h. UV analysis showed that by increasing the amount of pH, the amount of absorption and the band gap decreased and increased, respectively. [ABSTRACT FROM AUTHOR]