R-T-B Sintered Magnet Heavy Rare-Earth Diffusion Process
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Solution Overview
Problem
Existing methods for increasing the coercivity of sintered R-T-B based magnets, such as applying a slurry of heavy rare-earth element oxides or fluorides, require repeated applications and struggle with controlling the diffusion rate of heavy rare-earth elements, leading to limited and unstable coercivity enhancement.
Innovation Solution
A method involving a process chamber where a sintered R-T-B based magnet and an RH diffusion source, made of fluorides, oxides, or oxyfluorides, are heated to 800° C. to 950° C. while moving relative to each other, allowing for continuous and controlled diffusion of heavy rare-earth elements like Dy and Tb into the magnet.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If slurry of heavy rare-earth element compound is applied onto the sintered magnet surface, then the coercivity increases, but the diffusion rate cannot be controlled and repeated applications are needed
Solution Approach 1:
The patent replaces the mechanical slurry application method with a vapor-phase diffusion process. The heavy rare-earth element compound is heated to generate vapor that diffuses into the magnet surface, eliminating the need for repeated mechanical applications and enabling controlled diffusion rates through temperature and time parameters.
Solution Approach 2:
The patent changes the physical state of the heavy rare-earth element compound from solid slurry to vapor phase. By controlling the heating temperature and duration, the diffusion rate can be precisely adjusted, solving the problem of uncontrolled diffusion in slurry methods.
2Reliability
If heavy rare-earth element RH is added to increase coercivity, then the coercivity increases, but the remanence decreases
Solution Approach 1:
The patent applies heavy rare-earth element diffusion only to the surface region of the magnet where the grain boundary phase is located. This localized treatment increases coercivity at the critical surface regions without significantly affecting the bulk composition and remanence properties of the magnet.
3Reliability
If slurry is applied repeatedly to increase coercivity effect, then the coercivity increases, but the manufacturing complexity and time increase
Solution Approach 1:
The vapor-phase diffusion process allows continuous exposure of the magnet surface to the heavy rare-earth element vapor for the required duration. This continuous action achieves the desired coercivity enhancement in a single controlled process step, eliminating the need for multiple discrete slurry application and drying cycles.
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 enables stable and consistent diffusion of heavy rare-earth elements, resulting in sintered magnets with enhanced coercivity without compromising remanence, thus providing improved thermal stability and performance.
Implementation Method 1
diffusing the heavy rare-earth element RH from the surface of the sintered magnet and increasing the coercivity of the magnet
Implementation Method 2
heating means for heating the sintered R-T-B based magnet body and the RH diffusion source to a processing temperature
Data Source
AI summary
[Problem] To provide a heavy rare-earth element RH diffusion process that contributes greatly to mass production.[Solution] A method for producing a sintered magnet includes the steps of: providing a sintered R-T-B based magnet body; providing an RH diffusion source which is made of at least one of a fluoride, an oxide and an oxyfluoride that each include Dy and/or Tb; loading the sintered R-T-B based magnet body and the RH diffusion source into a process chamber so that the magnet body and the diffusion source are movable relative to each other and are readily brought close to, or into contact with, each other; and performing an RH diffusion process in which the sintered R-T-B based magnet body and the RH diffusion source are heated to a processing temperature of 800° C. through 950° C. while being moved either continuously or discontinuously in the process chamber.