Hydrothermal synthesis of monoclinic zirconia sol

In this study, we demonstrate a synthetic method of zirconia sol using ZrO(NO₃)₂·xH₂O as Zr⁴⁺ precursor, tetramethylammonium hydroxide as mineralizer, and oxalic acid as a complexing agent. X-ray diffraction, transmission electron microscopy, Raman spectroscopy, and UV–vis adsorption spectroscopy were used to characterize the nanocrystals. The effect of oxalic acid content on the growth of zirconia nanocrystals was investigated. Zirconia sol cannot be synthesized without oxalic acid. The oxalic acid content has no obvious effect on the phase formation of monoclinic zirconia. The transparent and monoclinic zirconia sol with particle size <10 nm was synthesized. This provides a new hydrothermal system for the synthesis of zirconia sol.