Effect of pH on Crystalline Phases of ZrO₂ Nanoparticles Synthesized via Supercritical Hydrothermal Method

Abstract

This study demonstrates the control of crystal phase of zirconium oxide (ZrO₂) nanoparticles synthesized from zirconium basic carbonate via supercritical hydrothermal method. The pH of the slurries of starting materials was adjusted using acetic acid. The lower pH reduces the amount of tetragonal phase of ZrO₂ nanoparticles, which are stabilized by CO₂ adsorbed on their surfaces. Single-phase monoclinic ZrO₂ nanoparticles are achieved at a pH of 3.0. This is because the pH of the slurries of the starting materials affects the states of CO₂-H₂O system. These results will lead to large-scale industrial production of phase-controlled ZrO₂ nanoparticles.