Rare-Earth Sintered Magnet Coercivity via Silver Nickel Gold Additives
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Solution Overview
Problem
The challenge is to develop a rare-earth sintered magnet with high coercivity and remanence without relying on the expensive and rare Dy element, while also minimizing the use of Al and Cu, which decrease remanence when added in excess.
Innovation Solution
A rare-earth sintered magnet composition including 12.0 to 15.0 at % of rare-earth elements like Nd and Pr, 5.5 to 8.5 at % of boron, and small amounts of additive metals such as silver (Ag), nickel (Ni), or gold (Au), along with inevitable impurities like Al, is used, with the additive metals being added in specific ranges to enhance coercivity without reducing remanence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Dy, Tb or Ho is added to increase coercivity, then coercivity is improved, but material cost increases and resource availability decreases
Solution Approach 1:
The invention changes the compositional parameters by adding specific elements (Al, Cu, V) in controlled amounts to achieve the desired coercivity without using expensive heavy rare-earth elements. The patent specifies precise compositional ranges: Al (0.1-5.0 at%), Cu (0.1-5.0 at%), and V (0.01-1.0 at%), which modifies the material parameters to achieve high coercivity through a cost-effective composition strategy.
Solution Approach 2:
The invention replaces expensive, rare heavy rare-earth elements (Dy, Tb, Ho) with more abundant and cheaper elements (Al, Cu, V). This substitution principle uses readily available elements that can be added in controlled amounts to achieve the same functional effect (high coercivity) without the high material cost and resource scarcity issues associated with heavy rare-earth elements.
2Reliability
If V is added to increase coercivity, then coercivity is improved, but the composition complexity increases
Solution Approach 1:
The invention applies partial action by adding V in a small, controlled amount (0.01-1.0 at%) rather than in large quantities. This small addition is sufficient to achieve the desired coercivity enhancement through synergistic interactions with Al and Cu, while minimizing the increase in composition complexity. The limited amount of V avoids over-complicating the material system while still achieving the functional benefit.
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
The approach results in a magnet with coercivity comparable to or exceeding that of conventional R—Fe—B based sintered magnets with added Cu or Al, while maintaining or increasing remanence, thus addressing the cost and resource concerns associated with Dy usage.
Implementation Method 1
an R2T14B phase (main phase) is a ferromagnetic phase contributing to magnetization
Implementation Method 2
Since Dy, Tb and Ho are rare-earth elements with a highly anisotropic magnetic field, the coercivity can be increased effectively
Implementation Method 3
sintering the resultant green compact
Data Source
AI summary
A rare-earth sintered magnet includes 12.0 at % to 15.0 at % of rare-earth element(s), which is at least one element selected from the group consisting of Nd, Pr, Gd, Tb, Dy and Ho and at least 50% of which is Nd and/or Pr; 5.5 at % to 8.5 at % of boron (B); a predetermined percentage of additive metal A; and iron (Fe) and inevitably contained impurities as the balance. The predetermined percentage of additive metal A includes at least one of 0.005 at % to 0.30 at % of silver (Ag), 0.005 at % to 0.40 at % of nickel (Ni), and 0.005 at % to 0.20 at % of gold (Au).