Refrigerant Materials Research Articles

Solvent-dependent Ln(III) clusters assembled by immobilization of CO2 in air: zero-field single-molecule magnets and magnetic refrigerant materials.

The automatic fixation of CO2 in air played a key role in the construction of Dy(III) single-molecule magnets (SMMs) and Gd(III) magnetic refrigeration molecular materials when Ln(III)Cl3 (Ln = Dy and Gd) was reacted with a new hydrazone Schiff base ligand {H2L = (E)-N'-(4-fluoro-2-hydroxybenzylidene)pyrimidine-4-carbohydrazide}, which is condensed from pyrimidine-4-carbohydrazide and 4-fluorosalicylaldehyde. Surprisingly, the small difference in methanol and ethanol solvents leads to dramatic changes in the structures of these Ln(III) cluster complexes. When methanol and ethanol participated in the reaction, a trapezoidal pyramid Dy(III) pentanuclear cluster [Dy5L5(OH)2(CO3)(O2COMe)(MeOH)3(H2O)]·3MeOH·3.5H2O (1) and a triangular prism Dy(III) hexanuclear cluster [Dy6L6(CO3)2(EtOH)2(H2O)2Cl2]·6EtOH (2) were obtained, respectively, and a tub-like Gd(III) octanuclear cluster [Gd8L8(CO3)4(MeOH)3(H2O)5]·12MeOH·3CH2Cl2·3.25H2O (3) and a trapezoidal pyramid Gd(III) pentanuclear cluster [Gd5L4(HL)(CO3)O(OH)(EtOH)5(H2O)2Cl]·EtOH·3H2O (4) were yielded, respectively. Notably, 1 contains not only the carbonate anion, but also the monomethyl carbonate anion as the bridging ligand, which are formed by immobilizing CO2 in air, while 2, 3 and 4 contain the carbonate bridging ligand only. Magnetic properties' investigations revealed that both 1 and 2 are zero-field SMMs, with Ueff/k values of 93.2 K and 133.5 K, respectively, while 3 and 4 show large magnetocaloric effects, with the largest -ΔSm values of 27.49 J kg-1 K-1 at 2.0 K for ΔH = 7 T for 3 and 27.58 J kg-1 K-1 at 2.5 K for ΔH = 7 T for 4.

Enhanced magnetocaloric effect accompanying successive magnetic transitions in TbMn2Si2-xGex compounds

The lack of magnetic refrigeration (MR) materials with high magnetocaloric effect (MCE) and large relative cooling power (RCP) in the temperature range required for hydrogen liquefaction (20 K–77 K) is a bottleneck for practical applications of MR cooling systems. The present investigation of TbMn2Si2-xGex compounds (x = 0.1, 0.2) by variable temperature neutron and synchrotron X-ray diffraction, magnetization and heat capacity measurements, establish that substitution of Si with Ge in TbMn2Si2 leads to a significant enlargement of the unit cell and modification of the magnetic properties. Two consecutive ferromagnetic first-order transitions occur below 77 K with the third transition from paramagnetism to a collinear antiferromagnetic state being determined around 500 K. The resultant plateau-like MCE with large RCP below 77 K in these designed compounds offers scope for application for hydrogen liquefaction. Detailed neutron investigation confirm that four magnetic states exist within the temperature range 5 K to 500 K, with two successive first-order magnetic transitions below 77 K responsible for the large MCE. Our specific heat studies provide evidence of strong contributions from the nuclear specific heat and the corresponding nuclear specific heat coefficients of A = 430 ± 50 mJ mol−1 K and A = 418 ± 60 mJ mol−1 K have been determined for TbMn2Si2-xGex with x = 0.1 and x = 0.2, respectively. The overlapping entropy curves near these successive transitions lead to a plateau-like magnetothermal effect as well as a large reversible MCE for both samples (e.g. ΔSMmax = 14.0 J/kg K and ΔTmax = 7.6 K; RCP = 379 J/kg for TbMn2Si1.9Ge0.1 for an applied field of 5 T) indicating that the material can operate over a wide temperature range – particularly for hydrogen liquefaction.

Tunable magnetocaloric effect towards cryogenic range by varying Mn:Ni ratio in all-d-metal Ni(Co)-Mn-Ti Heusler alloys

Cryogenic magnetic refrigeration is a highly efficient and environmentally friendly technique for gas liquefaction. However, refrigerant materials undergoing large magnetocaloric response at the interesting cryogenic range are dominated by critical elements (mainly rare-earth elements) which impedes practical applicability of such refrigeration systems. Therefore, there is a need for dedicated investigations on optimization of magnetocaloric response at cryogenic range by utilizing compositions that are rare-earth free. In this work, we synthesize the mechanically stable and rare-earth free, all-d-metal Ni35Co15Mn35Ti15 Heusler alloys and investigate the role of varying Mn:Ni ratio on the magnetostructural and magnetocaloric properties of the alloy system. The results of the microstructural characterization indicate homogenous composition for the investigated alloy series. As the Mn:Ni ratio increases from 1.01 to 1.10, the martensitic transition shifts from near-room temperature down to cryogenic region (120–140 K) while the magnetization of the austenitic phase remains unaltered. Isothermal entropy change as high as ∼ 13 J kg−1 K−1 at 1.5 T is achieved for the sample with the highest Mn:Ni ratio at the temperature region for natural gas liquefaction, which significantly surpasses the values previously reported in the literature for similar alloys. In addition to large magnetocaloric response, the martensitic transformation falls in an interesting temperature of the cryogenic region, paving the way for various low-temperature magnetocaloric applications.

Comparison of the environmental impact of typical packaging systems for food cold chain express based on life cycle assessment

With the rapid growth of e-commerce in the food industry, Food Cold Chain Express (FCCE) services have experienced significant expansion. These services typically entail extensive use of packaging items, including insulation boxes, insulation bags, and refrigeration materials, etc. This usage potentially leads to significant environmental burdens, encompassing resource consumption, greenhouse gas (GHG) emissions, and waste disposal. This study conducts a comparative environmental impacts analysis of two food cold chain packaging systems using life cycle assessment (LCA), for ice cream transportation. The reusable vacuum insulated panel (VIP) box packaging system demonstrates superior environmental performance when compared to the disposable expanded polystyrene (EPS) box packaging system across all evaluated impact categories. The results suggest that conclusions regarding lower environmental impact cannot be exclusively based on the choice of insulation material. The weight of the packaging and the transportation distance also exert a significant influence on the overall environmental performance of the systems. Furthermore, minimizing the environmental impact of dry ice usage by exploring alternatives is highlighted as a crucial aspect of sustainable packaging practices. The results provide valuable insights for optimizing cold chain packaging systems in the pursuit of environmental sustainability.

Large cryogenic magnetocaloric effect in borosilicate Gd3BSi2O10

The adiabatic demagnetization refrigeration which is based on the magnetocaloric effect (MCE) of magnetic materials is an effective technology to attain sub-Kelvin temperature. In this paper, we report the magnetocaloric property of Gd-based borosilicate Gd3BSi2O10. It experiences a second-order magnetic phase transition at test temperatures range. Owing to the high Gd3+ ion / anion ligand ratio and weak magnetic interaction, Gd3BSi2O10 exhibits a large magnetic entropy change of 59.1 J·kg−1·K−1 at 2.6 K for Δμ0H = 7 T, which is comparable to that of the top-ranked refrigerants operating in the cryogenic range. Besides, Gd3BSi2O10 compound exhibits considerable relative cooling power of 543.7 J·kg−1 for Δμ0H = 7 T. These properties demonstrate that Gd3BSi2O10 is a promising magnetic refrigeration material.

Effect of Cu doping on crystal structure, martensitic transformation, and magnetic properties of Mn2NiGa1−xCux (x = 0–0.7) ribbons

Magnetic shape memory alloys Mn2NiGa1−xCux (x = 0–0.7) melt-spun ribbons were synthesized, and their crystal structure, martensitic transformation, and magnetic and transport properties were studied. In Mn2NiGa1−xCux, unusual composition dependences of these properties were observed: the lattice parameter increases with Cu-doping, though Cu has a smaller atomic radius compared with Ga. The martensitic transformation temperature decreases with increasing Cu content at first and reaches a minimum at x = 0.3 and then increases rapidly as Cu content increases further. The variation tendency of magnetization is just opposite. When Cu content gets higher, a semiconductor-like to metal-like crossover in electron transport properties is observed. The martensite resistivity also changes from lower than that of austenite to higher than that. First-principles calculations indicate that these unusual properties are related to the competing occupation of Cu between A and D sites. Cu-doping can also enhance the metallic bonding in Mn2NiGa1−xCux, which can reduce the intrinsic brittleness and improve their mechanical properties. All this provides a fresh idea and method for the development of NiMn-based solid-state refrigeration materials.

Magnetic and magnetocaloric properties of polycrystalline Pr[formula omitted]Ca[formula omitted]MnO[formula omitted] (x [formula omitted] 0.85, 0.90, 0.95) compounds: Emergence of large inverse and conventional magnetocaloric effects

Magnetic and magnetocaloric effect have been investigated for the electron doped polycrystalline Pr1−xCaxMnO3 (x ∼ 0.85, 0.90, 0.95) compounds. The experimental outcomes indicate that the nature of the ground state is very much sensitive with the doping concentration. Pr0.15Ca0.85MnO3 compound exhibits antiferromagnetic ground state. In contrast to that ferromagnetic nature was found for the Pr0.10Ca0.90MnO3 and Pr0.05Ca0.95MnO3 compounds. Although, for x∼0.90 ferromagnetic phase was stable. However for x∼ 0.95, the ferromagnetic state is quite unstable. Additionally for the doping concentration x∼ 0.95, the anomalous nature was found in temperature dependent coercivity. Magnetocaloric effect study indicate that antiferromagnetic Pr0.15Ca0.85MnO3 compound exhibits large inverse magnetocaloric effect (10.5 J/kg-K at H = 70 kOe magnetic field). On the other hand, ferromagnetic Pr0.10Ca0.90MnO3 and Pr0.05Ca0.95MnO3 compounds show conventional magnetocaloric effect. The magnetocaloric entropy change for x∼0.90 compound is significantly large (7.5 J/kg-K at H = 70 kOe magnetic field) and comparable with the other reported magnetic refrigerant materials. Universal master curve for magnetic entropy change have been constructed for all the materials having inverse and conventional magnetocaloric effect by proper scaling of temperature axis.

Investigation of the triple peak magnetocaloric effects of Ni45Mn44Sn11 ribbons

The magnetocaloric effect (MCE) of Ni45Mn44Sn11 ribbons is simulated, with temperatures ranging from nearly 0 K to 313 K. The MCE of these ribbons exhibits triple peak behavior. Amazingly, three co-occurring peaks of both the inverse and conventional MCEs are found, one for each magnetic transition. Except for temperatures between 251 K and 273 K that correspond to an antiferromagnetic transition that shows an inverse MCE, the type of MCE in Ni45Mn44Sn11 ribbons is conventional. Consequently, materials with triple-peak MCE behavior, such as Ni45Mn44Sn11 ribbons, may provide a fascinating opportunity to obtain magnetic cooling over a wider temperature range than with conventional refrigerant materials, particularly Ni45Mn44Sn11 ribbons, which are inexpensive for use in magnetic refrigeration. Therefore, Ni45Mn44Sn11 ribbons are excellent magnetocaloric magnets for wide temperature ranges, including cryogenic and room temperatures.

Numerical and thermal analysis of a caloric refrigeration device operating near room temperature

The application of external stimuli such as the magnetic and electric field in magnetocaloric and electrocaloric materials, and stress and pressure in elastocaloric and barocaloric materials give rise to a new generation of a refrigeration technology based on caloric materials which are considered an emerging alternative to classical refrigeration. Active caloric regenerator (ACR) made in parallel plates is studied under a large number of materials with Comsol multiphysics for a 2D numerical model. In this work, we compare various types of caloric materials, in terms of their thermodynamic properties, working mechanisms, and potential applications as solid refrigerant on caloric refrigeration devices. For this purpose, the energy equation, Navier-Stocks equation, and continuity equation are considered to study the heat transfer phenomena in refrigerator. The water was used as a carrier fluid to transport the thermal energy from the solid refrigerants to heat exchanger. This study is performed at velocity 0.06 m/s and the frequency 2 Hz at room temperature. Among them, Gadolinium show the best results in term temperature span, coefficient of performance, and the cooling power, higher than every other caloric materials, conferring to magnetocaloric cooling globally the most promising system. Our analysis provides insights into the selection and optimization of caloric materials for caloric refrigeration, which can contribute to the development of sustainable energy systems.

Pr/ Co co-doping endows perovskite manganite with enhanced magnetic refrigeration capacity

It is recognized that new environmentally friendly and economical cooling methods are needed. In this paper, we focus on the effect of different doping amounts of Pr on the performance of magnetic refrigeration materials in the presence of trace doping of Co ions at the B-site. The samples La0.67Sr0.33−xPrxMn0.975Co0.025O3 (LSPMCO x = 0.10,0.125 and 0.15) in this paper were prepared by sol-gel method. The X-ray diffraction (XRD) and selected area electron diffraction (SAED) diffraction data determined that the samples were pure phases without impurities belonging to the R-3c space group (No. 167). Scanning electron microscope (SEM) and transmission electron microscope (TEM) showed that the samples were not regular particles of submicron size, and the size of the grains decreased gradually with increasing Pr doping. The experimental data have shown that the samples underwent second order phase transitions near the Curie temperature (Tc). Tc is closest to room temperature at 300 K at a doping level of 0.10. The maximum magnetic entropy change (−∆SMmax) at 5 T is 3.79 (J/kg∙K) (x = 0.15) and the relative cooling power (RCP) is 352.78 (J/kg) (x = 0.15). The results demonstrated that the doping of Pr has an enhanced effect on the performance of the magnetic refrigeration La0.67Sr0.33Mn0.975Co0.025O3 material. This may provide a reference for improving the performance of magnetic refrigeration materials in future research.

Enhanced room-temperature electrocaloric and pyroelectric responses around morphotropic phase boundary and energy storage performance of lead-free Ba0.85Ca0.15Hf0.10Ti0.90O3 ceramics sintered at various temperatures

The electrocaloric (EC) cooling and energy storage capabilities of Pb-free ferroelectrics are thought to be a promising technology for developing environmentally friendly refrigeration and energy storage systems. The EC performance, energy storage and pyroelectric response of sol-gel derived Ba0.85Ca0.15Hf0.10Ti0.90O3 (BCHT) ferroelectrics sintered at various temperatures are investigated here. It is thoroughly explored how sintering temperature affects the structural and electrical characteristics of BCHT ceramics. According to structural analysis by X-ray diffraction, the morphotropic phase boundary (MPB) of tetragonal and orthorhombic phases is evolved in BCHT ceramics sintered at higher temperatures of 1250 and 1350 °C. The density, grain size, and dielectric constant of BCHT ceramics increase when the sintering temperature rises from 1150 to 1350 °C. The BCHT ceramic sintered at 1250 °C exhibits the highest room temperature pyroelectric coefficient p ∼ 15.21 10−4 C/m2K and the various pyroelectric figure of merits calculated are Fi = 7.46 10−10 m/V, Fv = 0.033 m2/C, FD = 31.82 10−6 Pa−1/2, Fe = 103.44 J/m3K2, and Fe* = 24.85 10−12 m3/J respectively. At the ambient temperature, BCHT ceramic sintered at 1250 °C with MPB displayed a high EC temperature change ΔT ∼ 0.56 K and EC efficiency ΔT/ΔE ∼ 0.28 Kmm/kV under relatively low field ΔE ∼ 20 kV/cm. The highest EC temperature change ΔT ∼ 1.01 K is also observed in BCHT ceramics sintered at 1250 °C with corresponding ΔT/ΔE ∼ 0.50 Kmm/kV at 87 °C. The observed values are higher than the value reported for other lead-free materials. The maximum recoverable energy density Jrec ∼ 116.18 10−3 J/cm3 and corresponding efficiency η ∼ 71.34 % has been observed in BCHT ceramics sintered at 1250 °C. These findings indicate that BCHT ceramics offer a promising way to develop high-performance pyroelectric sensors, electrocaloric refrigeration, and energy storage materials.

Development of electrocaloric effect in BT-based lead-free ceramic via density adjustment strategy

Electrocaloric (EC) refrigeration materials have seen significant progress recently, with efficient Barium titanate-based (BT-based) lead-free materials particularly promising for microelectronics applications. However, their performance still lags behind their lead-based counterparts, highlighting the need for further improvements. This study employs a novel density adjustment strategy (DAS) to enhance the EC performance of (0.5-x)BCT-BTZ-xBST ceramics by carefully balancing the relationships among density, dielectric breakdown strength (BDS), and ΔT. Although ΔT intuitively decreases with increasing density, enhanced BDS can partially compensate for this decrease. An excellent EC performance with ΔT of 2.21 K and ΔT/ΔE of 0.471 K mm kV−1 is obtained in x = 0.5, together with a broader temperature span of 50.3 °C near room temperature, which surpasses or is comparable to other lead-free or lead-based ones. The results suggest that the DAS provides a promising approach for developing efficient EC, making speediness of application in EC devices.

High Cycle-Life Twistocaloric Cooling of Poly-p-Phenylene Benzodioxole Fibers.

It is an urgent need to develop efficient solid state cooling technologies and materials with high cycle life. Poly-p-phenylene benzodioxole (PBO) is a high performance fiber with excellent mechanical properties. In this work, for the first time, elasto- and twistocaloric cooling of PBO fibers by stretching and twisting of the PBO fiber bundles is reported. The cooling temperature reaches -0.4 and -1.3 K, for fiber stretching and twisting, respectively. A self-coiled PBO fiber achieves maximum cooling of -3.7K upon stretching by 35% strain, with an exceptionally high cycle life of 200000 times. During the twisting of the PBO fibers, reversible changes in the intensity of the diffraction peaks in X-ray diffraction patterns are observed. A strain-sensitive color change application is realized by coating a self-coiled PBO fiber with liquid crystallite dyes. This work provides new perspectives for PBO fibers as a high cycle-life solid-state refrigeration material.

Perspective role of phase change materials for energy efficiency in Algeria

Various measures have been considered in Algeria to improve energy efficiency but other effective ways are promising such as integration of phase change materials. The potential of these smart materials is reviewed for energy efficiency improvement in various systems including energy storage, refrigeration, and air conditioning, building envelope as well as cooling of photovoltaic systems. The literature review shows the high potential of this new class of materials. The survey indicates up to 12% energy savings due to integration of these new materials in refrigeration, 17.82% for air conditioning systems, and 10% for photovoltaics. The highest impact was achieved for the building envelope where energy savings of 34.8% were reported. On the other hand, limitations, challenges, and future concerns are revealed and highlighted for both researchers and policy-makers. New eco-friendly materials should be searched and adapted to the Algerian climate zones. Artificial intelligence can be a handy tool for material selection and optimization of thermal performance. Investment should be implemented together with adequate policy and awareness. Finally, the Algerian building regulations should be updated to include this new class of materials in buildings.

Large table-like magnetocaloric effect in boron-doped Er5Si3B0.5 compound

In this work, Er5Si3B0.5 compound with the Mn5Si3-type hexagonal structure was synthesized, and the structure, magnetic properties, and the magnetocaloric effect were investigated theoretically and experimentally. The magnetic measurement results show a complex successive magnetic transition below TN. However, the magnetization of the Er5Si3B0.5 compound below TN is saturated under lower magnetic field relative to the Er5Si3 compound. Theoretical calculation indicates that this was attributed to the enhanced inter-orbital exchange interaction after doping B element. The complicated successive magnetic transitions contribute to the table-like magnetocaloric effect observed in the Er5Si3B0.5 compound with a wide temperature region. The maximum magnetic entropy change and the temperature averaged entropy change (30) are 10.1 and 9.02 J/kg K for the Er5Si3B0.5 compound under varying magnetic fields from 0 to 5 T, respectively. The temperature averaged entropy change (30) is reduced by just 11% compared to the maximum magnetic entropy change. While presenting an ideal magnetic refrigeration material with a large table-like magnetocaloric effect for hydrogen liquefaction, our work also demonstrates the feasibility of regulating magnetic behavior through enhanced orbital exchange interactions to develop magnetic refrigeration materials with outstanding performance.

A Brief Review and Its Incorporation with Bibliometric Analysis of Phase Change Materials for Thermal Energy Storage

Reduction of Food Losses and Wastes (FLW) through the use of cold chain is one strategy applied in accelerating the SDGs goals of zero hunger. The application of Thermal Energy Storage (TES) based on PCM (Phase Change Material) is considered as one of best efforts for the simultaneous reduction of food losses and wastes, reduction of energy consumption as well as preserve the right temperature for food product. This paper presents the review of phase change material for thermal energy purposes and its bibliometric analysis. Bibliometric analysis on term of cold chain logistics show that there is correlation between cold chain and terms of optimization, vehicle routing, carbon emission, refrigeration, and phase change materials. The definition of TES and PCM, as well as the advantages of TES based on latent material are described in this paper. PCMs is classified into solid-solid, solid-liquid, solid-gas and liquid-gas based on its phase. The potential generation of gas and larger volume on solid-gas and liquid-gas PCMs limits the application of those two types of PCMs. PCMs is also classified according to the phase change temperature in which low, medium and high temperature PCMs. Organic, inorganic and composite based PCMs are the classification of PCMs based on the chemical composition. Among the types of PCMs, this paper present a deep review of paraffin based organic PCMs. The appearance of term of thermal conductivity in bibliometric analysis on term of organic phase change materials is due to organic PCMs commonly have low thermal conductivity

Magnetocaloric effect and phase transformation of LaFe11.0M0.5Si1.5 (M = Cu, Ni, Mg) alloys

La (Fe,Si)13 is a promising magnetic refrigerant material. In this paper, the effects of Cu, Ni and Mg substitution of Fe on the magnetocaloric effect and phase transition properties of LaFe11.5Si1.5 alloys were studied by first-principles calculations combined with experiments. Through scanning electron microscopy–energy-dispersive spectroscopy analysis, it was concluded that after Cu partially replaced Fe, the content of the 1:13 main phase significantly decreased to 61.49%, and the contents of the α-Fe and LaFeSi phases increased. Cu was not conducive to the formation of the main phase. After Mg partially replaced Fe, the content of the 1:13 main phase increased to 99.12%, and Mg promoted the formation of the main phase. The electronic structure of the alloy was reconstructed by density functional theory (DFT), and the effects of the doping atoms on the magnetic properties of the alloys were studied. The calculation results showed that Ni atoms had the same weak magnetism as that in the magnetic moment vector direction of Fe atoms, Cu and Mg atoms had magnetism opposite to that in the magnetic moment vector direction of Fe atoms, and all alloys showed a lower total magnetic moment. According to the Arrott curve and the field dependence method of the magnetocaloric effect (MCE), when Cu = 0.5 and Ni = 0.5, the alloy phase transition changed from a first-order phase transition to a second-order phase transition, and when Mg = 0.5, the alloy still had a first-order phase transition.

Magnetocaloric properties of shape-dependent nanostructured Gd2O3 oxide particles

Single-phase Gd2O3 nanostructures with different morphologies, such as nanoparticles, nanorods, nanospheres, and nanoplates, were synthesised. Gd2O3 1D nanorods and 2D nanoplate architectures were prepared via the hydrothermal method, while 3D hollow nanospheres were synthesised via homogeneous precipitation. The magnetic and magnetocaloric properties of Gd2O3 nanostructured particles were studied as functions of temperature and field. The material demonstrated typical paramagnetic behaviour in the measured temperature range of 3–300 K. The magnetic entropy change (−ΔS M ) was determined from the magnetic isotherms measured in the 3–38 K temperature range in the field up to 5 T. The maximum change in magnetic entropy value 11.2 J kg−1 K−1 for the nanoplate, 9.4 J kg−1 K−1 for the nanorod, 9.2 J kg−1 K−1 for the nanosphere, and 10.7 J kg−1 K−1 for the nanoparticle sample was observed at temperature 5 K for the magnetic field of 5 T. Owing to large these Gd2O3 nanostructured particles would be considered promising materials for magnetic refrigeration at cryogenic temperatures.

Structure, magnetism and magnetocaloric effects in Er5Si3B x (x = 0.3,0.6) compounds

We investigate the structure, magnetic properties, magnetic phase transitions and magnetocaloric effects (MCEs) of Er5Si3B x (x = 0.3, 0.6) compounds. The Er5Si3B x (x = 0.3, 0.6) compounds crystalize in a Mn5Si3 type hexagonal structure (space group: P63/cm) and exhibit a successive complicated magnetic phase transition. The extensive magnetic phase transitions contribute to the broad temperature range of MCEs exhibiting in Er5Si3B x (x = 0.3, 0.6) compounds, with maximum magnetic entropy change () and refrigeration capacity of 10.2 J⋅kg−1⋅K−1, 356.3 J/kg and 11.5 J⋅kg−1⋅K−1, 393.3 J/kg under varying magnetic fields 0–5 T, respectively. Remarkably, the δT FWHM values (the temperature range corresponding to ) of Er5Si3B x (x = 0.3, 0.6) compounds were up to 41.8 K and 39.6 K, respectively. Thus, the present work provides a potential magnetic refrigeration material with a broad temperature range MCEs for applications in cryogenic magnetic refrigerators.

Enhancing magnetocaloric properties of NiMnGa-based alloys via Dy micro-alloying and pseudoelastic cyclic training

Considerable interest to improve magnetic entropy change (ΔSm) and broaden working temperature interval (WTI) of NiMnGa ferromagnetic shape memory alloys (FESMAs) was stimulated by their applications as promising candidate materials for solid-state refrigeration. In the present study, we presented an approach to enhance the magnetocaloric properties of polycrystalline NiMnGa FESMAs via combining Dy micro-alloying and pseudoelastic cyclic training. The introduction of Dy elements established stable magneto-structural coupling transformation from the paramagnetic austenite to ferromagnetic martensite, accompanied by a large ΔSm [−16.42 J/(kg K)] and a widened WTI (∼15.98 K). Fascinatingly, it was demonstrated that the internal strain fields at phase interface between matrix and DyNi4Ga precipitates could assist the phase transformation nucleation, which significantly reduced the hysteresis loss from 20.84 J/kg of Ni54Mn25Ga21 alloy to 8.14 J/kg of Ni54Mn25Ga20.7Dy0.3 alloy. More importantly, the subsequent pseudoelastic cyclic training produced a strong ⟨110⟩NM preferred crystallographic orientation, which facilitated the magnetic alignment along easy magnetization axis. Consequently, the giant ΔSm value up to −24.25 J/(kg K) and effective refrigeration capacity RCeff of 198.77 J/kg were further achieved in the trained Ni54Mn25Ga20.7Dy0.3 alloy under an external magnetic-field change of 5.0 T.