Effect of Ga addition on the valence state of Ce and magnetic properties of melt-spun Ce17Fe78-xB6Gax (x = 0-1.0) ribbons

Abstract

The Ce17Fe78-xB6Gax (x=0-1.0) ribbons were fabricated by a melt-spinning technique in order to study the mechanism of the valence variation of Ce and their magnetic properties as well as improve the thermal stability of Ce-based rare earth permanent magnets. The systematic investigations of the Ce17Fe78-xB6Gax (x=0-1.0) alloys show that the room-temperature coercivity increases significantly from 352 kA/m at x = 0 to 492 kA/m at x = 1.0. The Curie temperature (Tc) increases monotonically from 424.5 K to 433.6 K, and the temperature coefficients of remanence (α) and coercivity (β) of the ribbons are better off from -0.56 %/K, -0.75 %/K for x = 0 to -0.45 %/K, -0.65 %/K for x = 0.75 in the temperature range of 300–400 K, respectively. The Ce L3-edge X-ray absorption near edge structure (XANES) spectrums reveal that there is more Ce4+ in ribbons under total electron yield than fluorescence yield as Ce has a high affinity with oxygen. The weight of Ce3+ increases while the weight of Ce4+ decreases in Ga-added alloys. The refined grain size and a more uniform microstructure are mainly attributed to the improved magnetic properties and thermal stability with Ga doping. This paper may serve as a reference for further developing the so-called gap magnets and the effective utilization of the rare earth resources.

Improvement of the microstructure and magnetic properties of (La,Ce)–Fe–B nanocrystalline ribbons

“…As the substitution of La increased from 0% to 50%, the lattice parameters of (La y Ce 100−y ) 16 Fe 78 B 6 ribbons expanded with a near-linear trend, as shown in Table 1 and Fig. 2(b).…”

“…Because La atoms may dissolve into the γ-Ce phase, the γ-Ce phase was named the RE-rich phase in this work. With an increasing La/Ce ratio and β -La phase generation, the fraction of the RE-rich phase decreased from 7.468 wt.% to 0.009 wt.% in (La y Ce 100−y ) 16 Fe 78 B 6 alloys.…”

“…A rare earth element content of 16 at.% was selected for its excellent performance in Ce-Fe-B type ribbons. The Rietveld refinement patterns for different y values in (La y Ce 100−y ) 16 Fe 78 B 6 ribbons are exhibited in Fig. 2(a).…”

“…Given the relatively high temperature (796.75 • C) of the invariant reaction (L↔ α-Fe+β -La), [34] the β -La phase formed when the La ratio varied from 15% to 50% and the mass fraction of the β -La phase increased drastically from 0.294 wt.% to 4.025 wt.%. The γ-Ce phase [35] is a product of a eutectic reaction at about 604 • C following the formula L↔CeFe 2 +γ-Ce and was found in (La y Ce 100−y ) 16 Fe 78 B 6 ribbons with a high Ce content. Because La atoms may dissolve into the γ-Ce phase, the γ-Ce phase was named the RE-rich phase in this work.…”

“…Herbst et al [10,11] and Soeda et al [12] reported the hard magnetic properties of Ce 2 Fe 14 B and (La,Ce) 2 Fe 14 B compounds, respectively. With the addition of Hf, [13] Ta [14] and Ga [15,16] to Ce-Fe-B type magnets, finer matrix phase grains and good magnetic properties have been obtained. However, the secondary phases (such as CeFe 2 , β -La phases, etc.)…”