Search

Compared with traditional techniques, solid‐state magnetocaloric phase transition materials (MPTMs), based on the giant magnetocaloric effect (GMCE), can achieve a higher energy conversion efficiency for caloric applications. As one of the most promising MPTMs, the hexagonal (Mn,Fe)2(P,Si)‐based compounds host some advantages, but the existing hysteresis and relatively unstable GMCE properties need to be properly tackled. In this study, it is found that substitutions with Ni, Pd, and Pt can maintain and even enhance the GMCE (≈8.7% maximum improvement of |Δsm|). For a magnetic field change of Δμ0H = 2 T, all samples obtain a |Δsm| in the range of 20–25 J kg−1 K−1 with a low thermal hysteresis ΔThys (≤5.6 K). The performance surpasses almost all other (Mn,Fe)2(P,Si)‐based materials with ΔThys (<10 K) reported until now. The occupancy of substitutional Ni/Pd/Pt atoms is determined by X‐ray diffraction, neutron diffraction, and density functional theory calculations. The difference in GMCE properties upon doping is understood from the competition between a weakening of the magnetic exchange interactions and the different degrees of orbital hybridization among 3d‐4d‐5d elements. The studies elaborate on the responsible mechanism and provide a general strategy through d‐block doping to further optimize the GMCE of this materials family. [ABSTRACT FROM AUTHOR]

Solid‐state caloric effects as intrinsic thermal responses to different physical external stimuli (magnetic‐, uniaxial stress‐, pressure‐, and electric‐fields) can achieve a higher energy efficiency compared with traditional gas compression techniques. Among these effects, magnetocaloric energy conversion is regarded as the best available alternative and has been exploited extensively for promising application scenarios in the last decades. This review systematically introduces the magnetocaloric effect and its applications, and summarizes the corresponding representative magnetocaloric materials, as well as important progress in recent years. Specifically, the review focuses on some key understandings of the magnetocaloric effect by utilizing state‐of‐the‐art technical tools such as synchrotron X‐ray, neutron scattering, muon spin spectroscopy, positron annihilation spectroscopy, high magnetic fields, etc., and highlights their importance toward advanced materials design and development. An overview of the basic principles and applications of these advanced techniques on magnetocaloric materials is provided. Finally, the challenges and perspectives on further developments in this field are discussed. Further in‐depth understanding and manufacturing technology advancement combined with fast‐developed artificial intelligence and machine learning are expected to advance the magnetocaloric energy conversion technology closer to real applications. [ABSTRACT FROM AUTHOR]

Magnetic refrigeration (MR) based on the magnetocaloric effect (MCE) has been recognized as an environmentally benign and energy-efficient cooling technology. Exploring suitable magnetocaloric materials is a crucial prerequisite for practical MR applications. We have herein provided a systematic investigation of the crystal structure, microstructure, electronic structure, magnetic phase transition, critical behavior, and MCE of the GdCoC compound featuring excellent cryogenic magnetocaloric performance by means of experimental determination and theoretical calculation. The GdCoC compound is crystallized in a simple layered tetragonal crystal structure with a P 4 2 / mmc space group and undergoes two successive ferromagnetic (FM) transitions along with a low-temperature weak antiferromagnetic (AFM) transition under low magnetic fields. Density functional theory calculations confirms the FM coupling of the Gd and Co intra-sublattice interactions, whereas AFM coupling for their inter-sublattice interaction. The magnetic transitions are merged in to one under high magnetic fields which has been confirmed to be second-order type and its critical behavior can be understood in the framework of tri-critical mean-field model, whereas the low-temperature weak AFM transition is belonging to the first-order type. The excellent magnetocaloric performance of the GdCoC compound was identified by the parameters of magnetic entropy change, adiabatic temperature change, temperature-averaged entropy change, relative cooling power, and refrigerant capacity, which are superior to most of the well-known magnetocaloric materials with similar working temperatures, making it attractive for practical cryogenic MR applications. [Display omitted] [ABSTRACT FROM AUTHOR]

The microstructure, phase constitution and corrosion behavior of non-stoichiometric La x Fe 11 Co 0. 8 Si 1.2 (x = 1.0, 1.2, 1.4, 1.6) magnetocaloric alloys were investigated. Annealed La x Fe 11 Co 0. 8 Si 1.2 compounds, containing the desired NaZn 13 -type matrix phase (1:13 phase), as well as a small α-Fe and La-rich phase content, exhibited high micro-galvanic corrosion in deionized water. The size of the La-rich phase in the La x Fe 11 Co 0. 8 Si 1.2 alloys varied with the La content. The refined La-rich phase in the La 1. 4 Fe 11 Co 0. 8 Si 1.2 alloy led to reduced galvanic corrosion and a more protective corrosion layer. Due to the internal stress of the corrosion product, the corrosion product of the coarse La-rich phase in the La 1. 6 Fe 11 Co 0. 8 Si 1.2 alloy easily cracked, leading to higher corrosion. Among these alloys, the La 1. 4 Fe 11 Co 0. 8 Si 1.2 alloy with a high content of the 1:13 phase and a small finer La-rich phase content, exhibited strong corrosion resistance. • Corrosion behavior of magnetocaloric La x Fe 11 Co 0·8 Si 1.2 (x = 1.0, 1.2, 1.4, 1.6) alloys was investigated. • A uniform distribution of fine La-rich and α-Fe phases can improve the corrosion resistance. • With excessive corrosion products, cracks appear on the corrosion layer due to internal stress. • The La 1·4 Fe 11 Co 0·8 Si 1.2 alloy exhibited the best corrosion resistance in the La x Fe 11 Co 0·8 Si 1.2 (x = 1.0, 1.2, 1.4, 1.6) alloy series. [ABSTRACT FROM AUTHOR]