Microstructure, magnetic properties and enhanced thermal conductivity in La(Fe,Co,Si)(13)/Nb magnetocaloric composites

摘要

La(Fe,Si)(13)-based series material has been recognized as one of the most preferred candidates as working materials for magnetic refrigeration. However, the intrinsic low thermal conductivity of La(Fe,Si)(13) compounds obstructs the ability of heat transfer during refrigeration. To enhance the thermal conductivity performance of La(Fe,Si)(13)-based composites, chemically stable Nb or Ta with high thermal conductivity has been added in several typical La(Fe,Co,Si)(13) matrixes with various Curie temperature (TC) and different types of phase transition. The microstructures, magnetic properties, magnetocaloric performances, and thermal conductivity in La(Fe,Co,Si)(13)/M (M = Nb and Ta) composites have been systematically investigated. Noticeably, although the maximal magnetic entropy change (Delta S-M) and refrigerant capacity (RC) slightly decrease with increasing Nb or Ta addition, the thermal conductivity improves remarkably. The enhance effect of the thermal conductivity for Nb or Ta addition in La(Fe,Co,Si)(13) matrixes is attributed to the formation of the secondary intermetallic phase (Fe2Nb or Fe7Ta3), which can be well explained in the frame of Nielsen model. The presented results would provide an alternative approach to enhance the thermal conductivity performances of La(Fe,Si)(13)-based composites regardless of phase transition type and transition temperature. (C) 2021 Elsevier B.V. All rights reserved.