R-T-B Sintered Magnet Void Reduction for Coercive Force
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Solution Overview
Problem
Conventional R-T-B based sintered magnets have voids that trap heavy rare earth elements, reducing their coercive force and increasing costs due to the inefficiency of these expensive elements.
Innovation Solution
The R-T-B based sintered magnet with a reduced void occupancy rate of 0.2% or less, featuring a concentration gradient of the first heavy rare earth element from the surface inward, and specific grain boundary phases, including a phase without Co and a uniformly distributed second heavy rare earth element, enhances coercive force utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If heavy rare earth elements are diffused into the R-T-B based sintered magnet, then coercive force is improved, but cost increases and efficiency decreases due to trapping in voids
Solution Approach 1:
The invention extracts and removes voids from the sintered magnet structure through optimized sintering processes and particle packing arrangements. By eliminating the voids that trap heavy rare earth elements, the diffusion process can proceed efficiently without element loss, directly resolving the contradiction between improving coercive force and maintaining element efficiency.
Solution Approach 2:
The invention performs preliminary actions by pre-optimizing the sintered magnet structure before diffusion, specifically by reducing void content and controlling grain boundary characteristics in advance. This preliminary structuring ensures that when heavy rare earth elements are subsequently diffused, they are efficiently utilized without being trapped, thereby improving coercive force while maintaining cost-effectiveness.
2Strength
If heavy rare earth elements are diffused into the sintered magnet, then coercive force is improved, but cost-effectiveness deteriorates
Solution Approach 1:
The invention changes critical parameters including void volume fraction (reducing to 0.2% or less), grain boundary phase composition (controlling R-rich phase content to 3 at% or less), and diffusion depth profiles. These parameter optimizations ensure that heavy rare earth elements are efficiently utilized, achieving high coercive force improvement with minimal element consumption, thereby maintaining cost-effectiveness.
Solution Approach 2:
The invention creates a composite grain boundary structure consisting of multiple phases with specific compositions and distributions. The controlled R-rich phase and other grain boundary phases work synergistically to enhance coercive force while minimizing heavy rare earth element consumption, improving cost-effectiveness through optimized material composition rather than simply increasing element content.
3Ease of manufacture
If voids are present in the sintered magnet, then manufacturing is easier, but heavy rare earth element utilization deteriorates
Solution Approach 1:
The invention applies local quality control by creating specific regional characteristics within the sintered magnet. The grain boundary regions are specifically engineered with controlled phase compositions and minimal void content, while the overall sintering process remains feasible. This localized optimization ensures high element utilization efficiency at grain boundaries without requiring complete elimination of all manufacturing challenges.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly improves coercive force while minimizing the amount of heavy rare earth elements used, thereby enhancing cost-effectiveness and magnetic properties.
Implementation Method 1
a first heavy rare earth element contained in a heavy rare earth compound is diffused from the surface toward the inside of an R-T-B based sintered magnet by attaching the heavy rare earth compound to at least a part of the surface of the R-T-B based sintered magnet and heating the heavy rare earth compound
Implementation Method 2
heating the heavy rare earth compound
Data Source
AI summary
An R-T-B based sintered magnet containing a first heavy rare earth element, in which R includes Nd, T includes Co and Fe, the first heavy rare earth element includes Tb or Dy, the R-T-B based sintered magnet has a region in which a concentration of the first heavy rare earth element decreases from the surface toward the inside, a first grain boundary phase which contains the first heavy rare earth element and Nd but does not contain Co is present in one cross section including the region, and an area occupied by the first grain boundary phase in one cross section including the region is 1.8% or less.