Enhancement of rotating magnetocaloric effect by Fe substitution in NdCo5-xFex alloys

Abstract

The effect of Fe substitution for Co on microstructure, phase constitution, and magnetocaloric properties was investigated in NdCo5-xFex (x = 0.2–1.0) alloys. The annealed NdCo5-xFex alloys are almost composed of the Nd(Co,Fe)5 matrix with a dispersed Nd2(Co,Fe)7 phase for x ≤ 0.6, and show entirely different microstructure of the Nd(Co,Fe)5 matrix surrounded by Nd2(Co,Fe)7, Nd(Co,Fe)3, and Nd(Co,Fe)2 phases for x ≥ 0.8. With increasing Fe content x from 0.2 to 1.0, two spin-reorientation transition temperatures are elevated from 262 to 310 K and 286 to 327 K, respectively. These field-oriented NdCo5-xFex alloys exhibit good rotating magnetocaloric properties, e.g., entropy changes of 2.25–3.66 J/kg K and refrigerant capacity of 188–233 J/kg in a magnetic field of 2 T. In addition, the rotating adiabatic temperature change reaches up to 2.5 K for NdCo4.2Fe0.8 in 2 T. The good combination of enhanced rotating magnetocaloric properties and adjustable working temperature of these alloys makes them suitable for use as refrigerants in room-temperature rotating magnetic refrigeration.