Microstructure and magnetocaloric effect in cast LaFe11.5Si1.5Bx (x=0.5, 1.0)

Phase formation, structure, and the magnetocaloric effect (MCE) in as-cast LaFe11.5Si1.5Bx (x=0.5, 1.0) compounds have been studied. The Curie temperatures, T-C, are similar to 211 and 230 K for x=0.5 and 1.0, respectively, which are higher than that of annealed LaFe11.5Si1.5 (T-C=183(K)), while the maximum magnetic entropy changes at the respective T-C under a magnetic field change of 0-5 T are 7.8 and 5.8 J/(kg K). Wavelength dispersive spectrometry (WDS) analysis shows that only a small fraction of boron atoms is dissolved in the NaZn13-type structure phase, and that the compositions of the as-cast LaFe11.5Si1.5Bx (x=0.5, 1.0) alloys are much different from the intended nominal compositions. These as-cast alloys exhibit second-order magnetic phase transitions and low MCEs. However, based on the relative cooling power, the as-cast LaFe11.5Si1.5Bx alloys are promising candidates for magnetic refrigerants over a wide temperature range. (C) 2009 Elsevier B.V. All rights reserved.