Leveraging Crystallization Pathway to Control Structure in Hf0.5Zr0.5O2 Nanoparticles

Abstract

Hf0.5Zr0.5O2‐based materials have garnered significant attention for applications requiring ferroelectricity at the nanoscale. This behavior arises due to the stabilization of metastable phases at room temperature. However, the synthesis of phase pure Hf0.5Zr0.5O2 remains a challenging problem in both thin films and nanoparticles. Herein, the crystallization of Hf0.5Zr0.5O2 nanoparticles from an as‐synthesized amorphous phase is studied. By tailoring the aggregate nature of the intermediate amorphous nanoparticles via different drying processes, the crystallization pathway can be altered, resulting in significant differences in crystal structure, crystallite size, and crystallite morphology after calcination. X‐ray diffraction (XRD) and Rietveld refinement show the dominant crystallographic phase changes from a monoclinic structure to a cubic structure for samples with decreased aggregation. Samples prepared via freeze drying exhibit the most aggregation control and correspond with the observation of single‐crystalline particle aggregates and branching structures attributed to a crystallization by particle attachment mechanism. Herein, differing crystallization pathways lead to unique crystal morphologies that stabilize the traditionally high‐temperature phases of Hf0.5Zr0.5O2‐based materials that are necessary for functional applications.