Study on the Hydrogenation Kinetics, Properties, and Stability of LaFe 11.5 Si 1.5 and LaFe 11.4 Si 1.6 Compounds

We have studied systematically the pressurecomposition-temperature (P-C-T) hydrogen absorption/release relation curves of LaFe11.5Si1.5 and LaFe11.4Si1.6 compounds. The effects of pressure, composition, temperature, and time on the process of hydrogenating have been investigated. The results indicate that the volume of unit cell can be expanded after hydrogenating without changing the cubic NaZn13-type crystal structure. The LaFe11.5Si1.5H1.6 and LaFe11.4Si1.6H0.5 compounds can be prepared separately under different hydrogen pressures at 423 K. The Curie temperature (T C) can be increased, the thermal hysteresis can be decreased, and the magnetic entropy change can be maintained at a high standard after hydrogenating in LaFe11.5Si1.5 and LaFe11.4Si1.6 compounds. With prolonged exposure time in air, the magnetic properties and magneto-caloric effect (MCE) can be maintained at a relatively ideal level, implying that the La(Fe, Si)13 hydrides have a good time stability.