The ΔT_ad values are high and reach their maximum within a narrow temperature range below 20 K. This indicates that Dy_1−xEr_xNi₂ solid solutions may be a viable option for refrigerants in magnetic cryocoolers suitable for hydrogen liquefaction.

Double perovskites are known for their special structures which can be utilized as catalyst electrode materials for electrochemical water splitting to generate carbon-neutral hydrogen energy. In this work, we prepared lanthanide series metal-doped double perovskites at the M site such as M₂NiMnO₆ (where M = Eu, Gd, Tb) using the solid-state reaction method, and they were investigated for an oxygen evolution reaction (OER) study in an alkaline medium. It is revealed that the catalyst with a configuration of Tb₂NiMnO₆ has outstanding OER properties such as a low overpotential of 288 mV to achieve a current density of 10 mAcm⁻², a lower Tafel slope of 38.76 mVdec⁻¹, and a long cycling stability over 100 h of continuous operation. A-site doping causes an alteration in the oxidation or valence states of the NiMn cations, their porosity, and the oxygen vacancies. This is evidenced in terms of the Mn⁴⁺/Mn³⁺ ratio modifying electronic properties and the surface which facilitates the OER properties of the catalyst. This is discussed using electrochemical impedance spectroscopy (EIS) and electrochemical surface area (ECSA) of the catalysts. The proposed work is promising for the synthesis and utilization of future catalyst electrodes for high-performance electrochemical water splitting.

We report on the arc melt syntheses of HoB₂ and Nb-substituted HoB₂ polycrystalline ingots and their magnetocaloric and microstructural properties. XRD data and microstructural analysis reveal that a nominal 10% Nb addition during synthesis results in changes to unit cell parameters and grain morphology. Interpretation of the refined cell parameters using Vegard’s law shows that Nb substitutes into HoB₂ with stoichiometry Ho_0.93Nb_0.07B₂. Arc-melted products are polycrystalline bulk samples containing minor phases such as Ho₂O₃, Ho, and HoB₄. Nb substitution results in a smaller grain size (~sub-micron) and a higher Curie temperature, T_C, compared to HoB₂. With a 10 T applied field, the maximum magnetic entropy, ΔS_M, for HoB₂ and for Ho_0.93Nb_0.07B₂, is 46.8 Jkg⁻¹K⁻¹ and 38.2 Jkg⁻¹K⁻¹ at 18 K and 21 K, respectively. Both samples show second-order phase transitions. Despite high totals of minor phases (e.g., ~10 wt.% and ~25 wt.%), the calculated relative cooling powers are greater than 1300 Jkg⁻¹ and 600 Jkg⁻¹ at 10 T and 5 T, respectively. The magnetocaloric properties of both samples are consistent with Holmium boride compounds prepared via alternative methods.

We report on arc melt syntheses of HoB2 and Nb-substituted HoB2 polycrystalline ingots and their magnetocaloric and microstructural properties. XRD data and microstructural analysis reveal that a nominal 10% Nb addition during synthesis results in changes to unit cell parameters and grain morphology. Interpretation of refined cell parameters using Vegard’s law shows that Nb substitutes into HoB2 with stoichiometry Ho0.93Nb0.07B2. Arc melted products are polycrystalline bulk samples containing minor phases such as Ho2O3, Ho and HoB4. Nb substitution results in a smaller grain size (~sub-micron) and a higher Curie temperature, TC, compared to HoB2. With a 10 T applied field, the maximum magnetic entropy, ΔSM, for HoB2 and for Ho0.93Nb0.07B2 is 46.8 Jkg-1K-1 and 38.2 Jkg-1K-1, at 18 K and 21 K, respectively. Both samples show second order phase transitions. Despite high totals of minor phases (e.g. ~10 wt.% and ~25 wt.%), calculated relative cooling powers are greater than 1,300 Jkg-1 and 600 Jkg-1, at 10 T and 5 T, respectively. Magnetocaloric properties of both samples are consistent with Holmium boride compounds prepared by alternative methods.