Submicron R{sub 2}Fe{sub 14}B particles

Journal Article · Sun May 15 04:00:00 EDT 2016 · AIP Advances

DOI:https://doi.org/10.1063/1.4944771· OSTI ID:22611755

Barandiaran, J. M. ^[1]; Salazar, D. ^[1]

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1. BCMaterials, Technology Park of Biscay E-48160 Derio (Spain)

Mechanochemical synthesis of submicron R{sub 2}Fe{sub 14}B particles with R = Dy, Nd, Pr has been performed successfully via high energy ball milling of rare-earth oxides, iron oxide and boron oxide in the presence of a reducing agent (Ca) and a dispersant material (CaO), followed by annealing at 800 - 900 °C. In the R = Nd system, we were able to fabricate particles embedded in a CaO matrix with coercivity (H{sub c}) of 10.3 kOe after annealing at 900 °C for 5 min. After washing off the dispersant, the H{sub c} was decreased to below 1 kOe because of hydrogen absorption that leads to the formation of the hydrated R{sub 2}Fe{sub 14}BH{sub x} phase that has a lower anisotropy. Upon removal of the hydrogen the coercivity was increased to 3.3 kOe. The average size of the Nd{sub 2}Fe{sub 14}B particles increases from 100 nm in a sample synthesized at 800 °C to 158 nm at 900 °C. The isotropic Dy{sub 2}Fe{sub 14}B particles showed a higher coercivity of 21 kOe in washed samples after annealing at 900 °C for 5 min. An average size of 71 nm is measured in samples synthesized at 800 °C and 107 nm at 900 °C. Fitting the high field M(H) measurements in Nd{sub 2}Fe{sub 14}B to the law of approach to saturation gave values for the magnetocrystalline anisotropy for the washed sample 2.23 × 10{sup 7} erg/cm{sup 3} and for the vacuum annealed sample 4.15 × 10{sup 7} erg/cm{sup 3}, both of which are lower than the bulk values. This would explain the lower values of H{sub c} observed in the particles.

• OSTI ID: 22611755
• Journal Information: AIP Advances, Journal Name: AIP Advances Journal Issue: 5 Vol. 6; ISSN AAIDBI; ISSN 2158-3226
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ABSORPTION
ANISOTROPY
ANNEALING
BORON COMPOUNDS
BORON OXIDES
CALCIUM OXIDES
COERCIVE FORCE
DYSPROSIUM COMPOUNDS
HYDROGEN
IRON COMPOUNDS
IRON OXIDES
MILLING
NEODYMIUM COMPOUNDS
PRASEODYMIUM COMPOUNDS
RARE EARTH COMPOUNDS
REDUCING AGENTS
SATURATION
SYNTHESIS
TERNARY ALLOY SYSTEMS