Theory/experience correlation of thermochromic perovskite crystallization

Monday, December 2, 2024 - 14:45
Sous titre
The classical Volmer nucleation model (CNT) has been applied to the crystallization of the SmNiO3 phase from its metastable amorphous phase. The correlation between the model, which predicts crystallization rate as a function of annealing temperature, and the experimental results obtained by XRD validated this CNT approach to solid/solid transformation, and enabled us to achieve some thermodynamic and mechanical properties not previously reported.

We present a thermodynamical model based on Volmer's nucleation theory adapted to the case of the perovskite nickelate SmNiO3 crystallization (SNO) from an amorphous (aSNO) thin film. This amorphous phase is synthesized via reactive magnetron sputtering and then subsequently annealed in air at temperatures between 725 and 925 K to crystallize it. This model allows to predict the theoretical nucleation rate of the crystallized perovskite phase according to the annealing temperature, the type of the nucleation (homogeneous and heterogeneous mechanisms) and to estimate some physical and thermodynamical data related to this transformation. A theoretical evaluation of the nucleation rate shows that the optimum temperature for crystallization is close to 800 K for which the nucleation rate can reach 1021 m-3.s-1 if considering both homogeneous and heterogeneous nucleation mechanisms. As the annealing temperature moves away from 800 K, the theoretical nucleation rate drops drastically, as observed experimentally by X-ray Diffraction (XRD) when we annealed 200 nm thick aSNO films. The good agreement between the presented model and the experimental crystallization results allows us to numerically evaluate some physical parameters not yet reported to date in the literature for SNO perovskites such as the surface energy between the amorphous and the crystallized SNO phases, the strain energy when the crystallization occurs and the enthalpy associated with crystallization.
 

 

Autors

 Silvère Barrat, Zil Fernández-Gutiérrez, Carlos Calvo-Mola, Pierre-Antoine Tostivint, Stéphanie Bruyère, David Pilloud, Fabien Capon

References

Acta Materialia - Octobre 2024

DOI

https://doi.org/10.1016/j.actamat.2024.120509


 

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