The diffusion process of La, Fe and Si through the La(Fe,Si)13 phase - A Fick’s 1st law based approach

Abstract

A model based on Fick’s 1st Law was used to describe the diffusion of La, Fe and Si through the La(Fe,Si)13 matrix and to determine the diffusion parameters (diffusion coefficients and activation energies). Materials based on this compound are promising solid refrigerants for magnetocaloric applications and annealing treatments are a common practice, however, literature has a lack of information regarding the diffusion parameters for such compounds. The model was implemented from experimental data obtained via microstructural characterization of La1Fe11.3Si1.7 samples annealed at different conditions of temperature and time. The diffusion coefficients obtained were about 10−10 cm²/s at 1423 K, and between 10−12 and 10−11 cm²/s at 1323 K, while the activation energies for Fe, La and Si were, respectively, 619 kJ/mol, 534 kJ/mol, and 704 kJ/mol. Annealing time and temperature were predicted based on the experimental diffusion parameter.