Synthesis pathways of (HfZrTiCe/La/Y)O2-x nanoparticles via benzyl alcohol route at critical temperature

Abstract

The controllable synthesis of high-entropy fluorite oxide (HEO) having large ionic radius mismatch remains a challenging due to poor understanding on nucleation. The (HfZrTiLn)-5HEO nanoparticles with 15 % ionic radius mismatch were synthesized via benzyl alcohol route at 220 °C-5 min in presence of PtCl₄ and Fe(acac)₃, exhibiting novel optical, electrical and magnetic properties. Nucleation pathways of the 5HEO at the critical temperature were elucidated by using a comparison study of conventional heating and microwave irradiation heating. Consistency of XRD patterns and STEM-EDX observation indicate that the resultant Hf-OBn monomers acted as the nucleation center of the 5HEO, determined by diffusion kinetics. The nucleation rate depended on the metal monomers assembly and esterification reaction, which was accelerated by water vapor pressure produced in-situ by $0.5\times {10}^{-4}\mathrm{mol}/l$ PtCl₄ catalyst. The Fe-metal organic cages derived from $1.5\times {10}^{-4}\mathrm{mol}/l$ Fe(acac)₃ additive served as the structure stabilizer of Zr/Ti monomers, and prevented early hydrothermal reaction route.