[Article] - TEM in situ crystallization of SmNiO3 nanoparticles

Thursday, December 11, 2025 - 21:37
Sous titre
Amorphous Sm–Ni–O nanoparticles produced by laser ablation were crystallized into the perovskite phase (SmNiO3) via in situ thermal treatments in the TEM. This study demonstrated that the initial Sm/Ni stoichiometry of the nanoparticles plays an important role during crystallization, as confirmed by analysis of high-resolution TEM images and by the increase in the Ni3+/Ni2+ ratio, a clear indicator of perovskite formation-measured by EELS.

Abstract

We report a direct in situ transmission electron microscopy (TEM) study of the crystallization of perovskite nickelate SmNiO3 from amorphous Sm−Ni−O nanoparticles. These nanoparticles, with a mean diameter of ∼30 nm, were generated by laser ablation of sputtered amorphous Sm−Ni−O films and deposited onto grids specially conceived to allow for in situ heating during TEM observations. In situ heating to 600 °C (ramp rate 600 °C/s, 30 s hold) within the TEM revealed the emergence of crystallized SmNiO3 domains, coexisting with secondary Sm2O3 or NiO phases in particles exhibiting off-stoichiometric Sm/Ni ratios. High-resolution TEM, fast Fourier transforms, and energy-dispersive X-ray spectroscopy demonstrated that initial chemical composition, rather than particle size, dictates phase evolution: near-stoichiometric particles form predominantly SmNiO3, whereas Sm- or Ni-rich particles undergo sequential crystallization of Sm2O3 or NiO followed by SmNiO3 nucleation. Core-loss electron energy-loss spectroscopy confirmed an order-of-magnitude increase in the Ni3+/Ni2+ ratio upon annealing, signifying perovskite formation alongside residual Ni2+ that can be attributed to oxygen vacancies or compositional inhomogeneities. A thermodynamic approach based on Gibbs free-energy landscapes rationalizes these pathways, and Gaussian fitting of SmNiO3 grain sizes versus Ni content reveals maximum domain growth at ideal 1:1 Sm/Ni stoichiometry. These findings elucidate nanoscale crystallization mechanisms in strongly correlated oxide nanoparticles and offer a new potential route to integrating this material in new functional device architectures.

Autors

Carlos Calvo-Mola, Stéphanie Bruyère, Vicente Torres-Costa, Silvère Barrat

References

J. Phys. Chem. C 2025, 129, 35, 15806–15814

DOI 

https://doi.org/10.1021/acs.jpcc.5c04120
 


 

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