A core-shell phenomenon maintain the magnetocaloric properties of the ternary silicide Gd6Co1.67Si3 during water flux ageing

Madhu Chennabasappa (1) , Bernard Chevalier (1) , Michel Lahaye (1, 2) , Christine Labrugère (2, 1) , Olivier Toulemonde (1)

1 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux
2 CeCaMA - Centre de Caractérisation des Matériaux Avancés

Ageing effect phenomenon is artificially stimulated on room temperature magnetocaloric material Gd6Co1.67Si3 by using constant flux of water up to time interval of 3 months. A core-shell model of oxide layer formation (SiOx-Gd2O3) on surface of Gd6Co1.67Si3 due to corrosion is justified using spontaneous single metal electrochemical reactions. The model is first proposed by a detailed microstructure study using Electron Probe Micro-Analysis, X-ray diffraction experiments on the aged slab revealing Gd2O3 phase and elemental depth profile analysis against time by Auger spectroscopy. It is further supported by surface chemical bonding study using X-ray Photoelectron Spectroscopy (XPS) concentrated on Si2p and O1s spectra. It is finally demonstrated that the room temperature bulk magnetocaloric performances of the material are not affected even under formation of corroded layer at the micron level scale. The Gd2O3 shell certainly acts as a passivation layer.

Mots clés: Ageing; Gadolinium based intermetallics; Magnetocaloric effect; XPS; AES; EPMA

Domaines: Matériaux

Madhu Chennabasappa, Bernard Chevalier, Michel Lahaye, Christine Labrugère, Olivier Toulemonde. A core-shell phenomenon maintain the magnetocaloric properties of the ternary silicide Gd6Co1.67Si3 during water flux ageing. Journal of Alloys and Compounds, 2014, 584, pp.34-40. ⟨10.1016/j.jallcom.2013.08.211⟩. ⟨hal-00873638⟩