Effect of excess lanthanum on corrosion and magnetocaloric property of LaFe11.5Si1.5 compounds

The corrosion and magnetocaloric property of LaFe11.5Si1.5 compound with excess La from 0 wt% to 15 wt % were investigated by a scanning electron microscope (SEM), electrochemical workstation and a vibrating sample magnetometer (VSM). With the increase of excess La from 0 wt%, 5 wt% to 10 wt% and 15 wt%, most of the La-rich phase changes from granular La2O3 phase to grain boundary LaFeSi phase. The La2O3 is more stable than the main 1:13 phase, while LaFeSi phase is easy to be corroded than the 1:13 phase. The maximum entropy change -Delta S-max is 18.60, 21.48, 19.66 and 16.28 J/(kg.K) for 0 wt%, 5 wt%, 10 wt% and 15 wt% excess of La, respectively. As adding 5 wt% excess La in LaFe11.5Si1.5 compound leads to nearly single 1:13 phase, the largest magnetic entropy change and better corrosion resistance are obtained. (C) 2019 Chinese Society of Rare Earths. Published by Elsevier B.V. All rights reserved.