High‐Cerium‐Content Fe–Ce–Nd–B Sintered Magnets with High Coercivity

Abstract

Ce substitution of Nd in FeNdB sintered magnets is very interesting for reasons of resource efficiency, sustainability and costs. However, the magnetic properties of high Ce‐content magnets are poor. This is mainly due to the lower values of intrinsic magnetic properties of Fe14Ce2B compared to Fe14Nd2B as well as the Laves phase Fe2Ce, which is formed in the grain boundaries and forms flat aggregates for higher Ce‐content. In this paper, sintered magnets with 75 at% degree of substitution of the composition Fe70.9‐[(Ce1‐xLax)0.75Nd0.25]18.8‐B5.8‐M4.5 (M = Co, Ti, Al, Ga, Cu, 0 ≤ × ≤ 0.3) are produced and analyzed. It is shown that a new rare earth rich grain boundary phase is formed adding La and that the Laves phase fraction can be reduced by up to 85%. With increasing La content, the remanence and Curie temperature increase and the temperature coefficient of Hc improves. A coercivity, remanence and maximum energy density of up to µ0Hc = 0.74 T, Jr = 0.98 T and (BH)max = 139.9 kJ/m3 have been achieved.This article is protected by copyright. All rights reserved.

Exploring Sintered Fe-(Ce, Nd)-B with High Degree of Cerium Substitution as Potential Gap Magnet

“…The addition of La modifies the stability window for the Fe2Ce phase and also has a favorable effect on the temperature stability of the magnetic properties. This enables higher values for the remanence and (BH)max even at higher Ce contents such as 75% with still passable coercivities (even if smaller than without La addition) [37]. It has to be noted that the comparison with sintered magnets from the literature can only be made qualitatively.…”

“…When Ce-based strip-cast flakes are used at much higher Ce contents (>80%), the soft magnetic α-Fe phase is precipitated, and the hard magnetic properties of Ce-based sintered magnets are deteriorated significantly [32,33]. All this may be the reason why sintered Fe-(Nd, Ce)-B magnets with a high degree of Ce substitution (sometimes with addition of lanthanum) have only rarely been investigated [26,[34][35][36][37]. For example, coercivities between Hc = 724 kA/m or µ0Hc = 0.91 T (45 at% degree of Ce substitution) and 143 kA/m or 0.18 T (86 at% degree of Ce substitution) have so far been achieved in these references for higher Ce substitution degrees in sintered magnets (for further details, see also Section 4.2).…”