Ligand-Mediated Crystallization Pathway and Interfacial Ionic Transport in Colloidal La–Zr–O Nanophases

Colloidal synthesis offers a versatile route to complex oxide nanomaterials, yet controlling phase selection and ionic transport in multicomponent oxide systems remains challenging. Here, we investigate the structural evolution and ionic transport behavior of lanthanum–zirconium oxide (La–Zr–O) nanophases synthesized via a colloidal hot-injection approach. By systematically varying reaction temperature and dwell time, we access amorphous La–Zr–O networks and nanocrystalline pyrochlore-like phases. Variable-temperature powder X-ray diffraction and total scattering pair distribution function analyses reveal that crystallization proceeds through the emergence of pyrochlore-related local order coupled to ligand decomposition and removal, leading to nanoscale structural heterogeneity rather than phase-pure bulk oxides. Electrochemical impedance spectroscopy performed under controlled temperature and uniaxial pressure demonstrates that ionic conductivity in cold-pressed nanocrystal assemblies ranges from ∼10–8 to ∼10–7 S cm–1, with apparent activation energies near zero (Ea ≈ 0–0.05 eV) that are characteristic of interface- and contact-dominated transport rather than bulk lattice diffusion. These results establish clear links between ligand chemistry, local structure, and interfacial ion transport in colloidal oxide systems. More broadly, this work provides mechanistic insights into crystallization pathways and nanoionic transport in multicomponent oxide nanomaterials, with implications for the rational design of colloidally derived solid electrolytes.