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Skutterudites are one of the most efficient materials for use in thermoelectric applications. From an industrial point of view, along with the high efficiency of thermoelectric materials, it becomes actual to develop a rapid, scalable, and energy-efficient fabrication technique. In this regard, mechanochemical synthesis has gained significant attention as a promising approach. In this work, we demonstrate the applicability and the potential of mechanochemical synthesis for the preparation of p-type skutterudites using Yb0.75Ce0.25Fe3.5Co0.5Sb12 composition as an example. In fact, the time spent on a full cycle of synthesis of bulk samples is less than 10 h, and the highest figure of merit value was 0.62, which is comparable to the values for similar compositions from previously works, where the time for synthesis is tens of times longer. [ABSTRACT FROM AUTHOR]

Natural gases have played a significant role in different sectors of the global economy. Recent analyses have shown that the world's gas consumption doubled over the last three decades; further growth of the gas consumption is predicted, rising to be 23%–28% of the total primary energy demand by 2030. Therefore, liquefaction of natural gases rapidly gains global importance. In this context, magnetic refrigeration emerges as a modern energy-saving technique, which is an alternative to the traditional gas-compression refrigeration. This paper is devoted to the study of the magnetocaloric effect in magnetic fields up to 10 T on a representative of the Laves phase alloys, GdNi2, which is considered as a perspective material for liquefaction of natural gases. For a magnetic field change of 10 T, the magnetic entropy change ΔSm ≈ −17 J/kg K and the adiabatic temperature change ΔTad ≈ 6.8 K was attained around Curie temperature TC = 70 K. The maximal value of the adiabatic temperature change measured directly in pulsed magnetic fields up to 50 T is ΔTad ≈ 15 K. [ABSTRACT FROM AUTHOR]

The results of in situ studies of the magnetostructural transition occurring in single crystals of an Ni2.19Mn0.81Ga Heusler alloy are presented in this paper. The formation of martensitic twins on exposure to high magnetic fields up to 10 T in the magnetostructural transition regime was observed using an indigenously developed optical microscope. Experiments on magnetization were performed on single crystals of Ni2.19Mn0.81Ga in high magnetic fields, a phase diagram between magnetic field and temperature was constructed, and the isothermal entropy change was estimated. Based on the experimental data and the results from optical microscopic examination, the influence of magnetic field and thermal cycling on martensitic twins and, in turn, on the magnetocaloric effect, is discussed. [ABSTRACT FROM AUTHOR]

Measurements of the adiabatic temperature change (ΔT) and the specific heat transfer (ΔQ) of Ni2.18Mn0.82Ga Heusler alloy were taken in order to quantify the direct giant magnetocaloric effect of the alloy when it is in the vicinity of magneto-structural phase transition (PT) from paramagnetic austenite to ferromagnetic martensite, and their results are presented. A new vacuum calorimeter was used to simultaneously measure ΔT and ΔQ of magnetocaloric materials with a Bitter coil magnet in fields of up to H=140 kOe. Other thermomagnetic properties of this alloy were investigated using standard differential scanning calorimetry and PPMS equipment. The maximal values of magnetocaloric effect in H=140 kOe were found to be ΔT=8.4K at initial temperature 340K and ΔQ=4900 J/kg at 343 K. Using this direct method, we show that the alloy indeed demonstrates the largest value of ΔQ as compared with previously published results for direct measurements of magnetocaloric materials, even though at 140 kOe the magnetic field-induced magnetostructural PT is still not complete. [ABSTRACT FROM AUTHOR]

Dysprosium possesses the highest magnetic moment among the rare-earth elements and undergoes a second-order magnetic phase transition to a complex helical antiferromagnetic ordering at Néel temperature TN = 180 K which is followed by a transformation to the ferromagnetic ordering at a lower temperature. Superior magnetic properties and tunability of the magnetic phase transition temperatures make Dy and its solid solutions perspective for the use in technology of magnetic refrigeration at cryogenic temperatures, specifically for the liquefaction of natural gases. In this work we report on the evolution of magnetic properties in solid solutions of Dy100-xYx (x = 0 – 15). It was found that the dilution of Dy magnetic subsystem by a non-magnetic Y has rather a weak impact on the magnetization saturation, which decreases from Ms ∼280 A⋅m2/kg in the x = 0 sample to Ms ∼259 A⋅m2/kg in the x = 15 sample. As a consequence, the isothermal magnetic entropy change was found to decrease slightly in the series of Dy100-xYx (x = 0 – 15) solid solutions. [ABSTRACT FROM AUTHOR]

(Ni48Co6)Mn26Al20 polycrystalline ribbons with B2 structure at room temperature are investigated. Considering the presence of competing magnetic interactions, Arrott-plot analysis gives TN ∼ 170 K. A broad ferromagnetic-paramagnetic transition (TC) is observed at ∼200 K. H-T phase-diagram is used to validate the presence of competing exchange interactions that persist till very close to TC. Based on Néel theory, a cluster model is used to explain the presence of ferromagnetic and antiferromagnetic clusters in the sample. Formation of ferromagnetic clusters can be understood in terms of positive exchange interactions among the Mn atoms that are neighboring Co atoms located at Ni sites. [ABSTRACT FROM AUTHOR]

Structural, magnetic, and transport properties of Ni52+xMn26-xAl22 (1 ≤ x ≤ 5) melt-spun ribbons have been characterized by a variety of experimental techniques. As the composition changed from x = 1 to x = 5, the martensitic transition temperature T0 [ = (Ms + Af)/2] was found to increase from 277 K to 446 K which was attributed to an increase in the valence electron concentration e/a. In the martensitic state, all the samples demonstrate an anomalous semiconducting behavior of electrical resistivity ρ. This uncommon feature of the transport properties has been ascribed to the existence of a gap (Eg ∼ 0.1 eV) at the Fermi level. A crossover from semiconducting to metallic behavior of ρ observed in the martensitic state of Ni57Mn21Al22 is presumably related to a spin-density wave formation at the Neel temperature TN ≈ 300 K. Analysis of a low-temperature (T < 60 K) part of the resistivity curves and comprehensive magnetic measurements of a Ni57Mn21Al22 (x ≤ 5) sample provide grounds for the conclusion that the splitting of zero-field cooling and field cooling magnetization curves observed at low temperatures is due to a spin-glass state that is formed below the freezing temperature Tf. [ABSTRACT FROM AUTHOR]