ThMn12-Type Rare Earth Magnet High-Temperature Coercivity
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Solution Overview
Problem
Current rare earth magnets, including those with a ThMn12-type crystal structure and Nd—Fe—B-based magnets, exhibit insufficient magnetization and coercivity at high temperatures, which is a limitation for applications in high-temperature environments such as automotive motors.
Innovation Solution
A rare earth magnet with a ThMn12-type crystal structure main phase and a sub-phase comprising Sm5Fe17, SmCo5, Sm2O3, and Sm7Cu3 phases, where the sub-phase volume fraction is between 2.3% and 9.5%, and the α-Fe phase is 9.0% or less, with specific elemental replacements and compositions to enhance magnetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Dy is added to Nd-Fe-B-based magnet to ensure coercivity at high temperature, then coercivity is improved, but production cost increases and element availability decreases
Solution Approach 1:
The patent combines Nd-Fe-B main phase with Sm-Co sub-phase particles to achieve high temperature coercivity. This merging of two different magnet systems allows the Sm-Co phase to provide thermal stability and coercivity enhancement without requiring Dy addition to the Nd-Fe-B matrix, thereby avoiding the cost and availability issues associated with dysprosium.
Solution Approach 2:
The invention creates a composite magnet structure where Nd-Fe-B main phase particles are combined with Sm-Co sub-phase particles. This composite approach leverages the high magnetization of Nd-Fe-B and the high coercivity/thermal stability of Sm-Co, achieving superior overall performance without relying on expensive Dy elements.
Data Source
AI summary
A rare earth magnet having a main phase and a sub-phase, wherein the main phase has a ThMn12-type crystal structure; the sub-phase contains at least any one of an Sm5Fe17-based phase, an SmCo5-based phase, an Sm2O3-based phase, and an Sm7Cu3-based phase; assuming that the volume of the rare earth magnet is 100%, the volume fraction of the sub-phase is from 2.3 to 9.5% and the volume fraction of an α-Fe phase is 9.0% or less; and the density of the rare earth magnet is 7.0 g/cm3 or more.