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Magnetocaloric Properties and Microstructures of HoB2 and Nb-Substituted HoB2
Mahboobeh Shahbazi1,2, Ali Dehghan Manshadi3, Kiran Shinde4
1Centre for Materials Science and School of Chemistry and Physics, Queensland University of Technology, Brisbane, QLD 4001, Australia.
Materials (Basel, Switzerland)
|February 26, 2025
Summary
Niobium substitution in Holmium diboride (HoB₂) enhances its magnetic properties, leading to a higher Curie temperature (TC) and significant magnetocaloric effects, crucial for magnetic refrigeration applications.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Solid State Chemistry
Background:
- Holmium diboride (HoB₂) is a material with potential magnetocaloric properties.
- Understanding the impact of doping on its magnetic and microstructural characteristics is essential for optimizing its performance.
Purpose of the Study:
- To synthesize and characterize Niobium (Nb)-substituted HoB₂.
- To investigate the effects of Nb substitution on the magnetocaloric properties and microstructure of HoB₂.
Main Methods:
- Arc melt synthesis of polycrystalline HoB₂ and Nb-substituted HoB₂ ingots.
- X-ray diffraction (XRD) for structural analysis and unit cell parameter determination.
- Microstructural analysis to observe grain morphology and size.
- Magnetocaloric property measurements, including magnetic entropy change (ΔSM) and relative cooling power (RCP).
Main Results:
- Nb substitution was confirmed with a stoichiometry of Ho₀.₉₃Nb₀.₀₇B₂.
- Nb substitution led to smaller grain sizes (~sub-micron) and an increased Curie temperature (TC).
- Maximum magnetic entropy changes (ΔSM) of 46.8 Jkg⁻¹K⁻¹ (HoB₂) and 38.2 Jkg⁻¹K⁻¹ (Ho₀.₉₃Nb₀.₀₇B₂) were observed at 10 T.
- High relative cooling powers (RCP) were calculated despite the presence of minor phases.
Conclusions:
- Niobium substitution effectively modifies the microstructure and enhances the magnetocaloric properties of Holmium diboride.
- The observed magnetocaloric behavior is consistent with other Holmium boride compounds.
- Nb-substituted HoB₂ shows promise for magnetic refrigeration applications.
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