Significant Reduction of Phase-Transition Hysteresis for Magnetocaloric (La 1-xCe x) 2Fe 11Si 2H y Alloys by Microstructural Manipulation

Abstract

First-order magnetostructural phase transitions are inevitably accompanied by large hysteresis, which evokes non-ignorable energy losses a main challenge for the utilization of giant magnetocaloric effect (MCE) materials in the emerging magnetic cooling technology. In this work, we present a novel approach to reduce the hysteresis and simultaneously to remain the giant entropy change for La-Fe-Si-based MCE alloys by microstructural manipulation. The microstructure evolution is comprehensively studied by high angle annular dark field-scanning transmission electron microscope (HAADF-STEM), three-dimensional atom probe (3DAP) and geometric phase analysis (GAP). For the LaFe13-xSix system via co-doping of Ce and H atoms, we have observed the appearance of nano-sized grains (5 ~ 50 nm) that is totally different from the conventional compositions. Such refinement can be ascribed to the release of internal stresses caused by the inhomogeneous distribution of hydrogen atoms. With the increase of Ce content for (La1-xCex)2Fe11Si2Hy alloys, the value of hysteresis losses can be significantly reduced from 48.3 to 0.6 J kg-1. More importantly, the magnetostructural transition keeps the obvious first-order type, which leads to a large adiabatic temperature change of 2.2 K in 1.3 T upon 105 magnetic cycles, as well as a high refrigeration capacity of 89.4 J kg-1.