Continuous supercritical hydrothermal synthesis of stabilized ZrO₂ nanocomposites: Doping mechanism of typical metals and transition elements

In this study, Mg, Ce, Y and La-doped nano-zirconia particles were successfully obtained by continuous supercritical hydrothermal synthesis combined with nanotechnology and crystal stabilization technology. Through detailed characterization and analysis of the structure, crystal form, grain size of the particles and by-products, the doping amount of different element dopants was optimized, and the stable pathway of tetragonal and cubic phases was proposed. Moreover, the doping mechanisms of different elements and phase diagram of doped nano-zirconia were revealed. The results show that the crystal form is determined by the doping amount, ionic radius and intrinsic properties of ions. Y and Ce doping can completely stabilize the tetragonal or cubic phase without the formation of by-products. Mg and La doping produce by-products of Mg(OH)₂ and La₂O₂CO₃. As the ionic radius increases, the radius mismatch with Zr⁴⁺ leads to a stronger ability to stabilize the tetragonal or cubic phase. At the same time, minimum dopant for stable tetragonal or cubic phases will decrease.