Ferrite Sintered Magnet Composition for High Torque Motors
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Solution Overview
Problem
Ferrite sintered magnets with a magnetoplumbite-type crystal structure require improvement in residual magnetic flux density (Br) and squareness for applications in small-sized motors with high torque requirements.
Innovation Solution
A ferrite sintered magnet composition containing Ca, metal elements A (Sr, Ba, Pb), metal element R (rare-earth elements including Y and La), and metal element M (Co, Ni, Zn, Al, Cu, Cr) with specific atomic ratios, optimizing the magnetic properties by controlling the proportions of these elements to enhance Br and squareness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional M-type ferrite composition is used, then manufacturing is simple, but residual magnetic flux density (Br) and squareness are insufficient
Solution Approach 1:
The patent applies parameter changes by optimizing the atomic ratios of multiple metal elements in the ferrite composition. Specifically, it controls Ca content at 0.15-0.50, rare-earth elements R at 0.45-0.80, metal element A at 0.01-0.10, metal element M at 0.10-0.50, and Bi at 0.01-0.10, with Fe balancing to 1.00. This precise parameter optimization achieves high Br (4.8-5.2 kG) and squareness (0.85-0.95) while maintaining manufacturing feasibility through standard sintering processes.
Solution Approach 2:
The patent employs composite materials by creating a multi-element ferrite system that combines Ca, rare-earth elements (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y), metal elements (Co, Ni, Zn, Al, Cu, Cr), and Bi. This composite approach leverages the synergistic effects of different elements: Ca and rare-earth elements provide high magnetization, while metal elements M enhance coercive force, and Bi improves squareness by suppressing secondary phase formation.
2Manufacturing precision
If higher magnetic properties are pursued, then Br and squareness improve, but sintering temperature must be increased
Solution Approach 1:
The patent utilizes parameter changes to achieve high magnetic properties at lower sintering temperatures through optimized composition. The specific atomic ratios of Ca (0.15-0.50), rare-earth elements (0.45-0.80), and metal elements M (0.10-0.50) create a composition that facilitates sintering at 1100-1300°C while achieving Br of 4.8-5.2 kG and squareness of 0.85-0.95. The Bi addition (0.01-0.10) specifically aids in lowering sintering temperature by suppressing secondary phase formation.
Solution Approach 2:
The patent uses Bi as an intermediary element that mediates between composition and sintering process. Bi (at 0.01-0.10 atomic ratio) acts as a sintering aid that promotes grain boundary formation and suppresses unwanted secondary phases, enabling lower sintering temperatures while maintaining high magnetic properties. This intermediary element facilitates the sintering process without compromising the final magnetic performance.
3Reliability
If conventional compositions are used, then manufacturing is easier, but low-temperature demagnetization occurs
Solution Approach 1:
The patent applies parameter changes by optimizing the composition to achieve high coercive force (HcJ) and resistance to low-temperature demagnetization. The metal elements M (Co, Ni, Zn, Al, Cu, Cr) at 0.10-0.50 atomic ratio specifically enhance coercive force, while the balanced ratio of Ca (0.15-0.50) and rare-earth elements (0.45-0.80) ensures high magnetization. This composition achieves HcJ of 2000-4000 Oe and maintains magnetic properties down to -40°C.
Solution Approach 2:
The patent employs composite materials with a multi-element system designed to resist demagnetization. The combination of Ca, rare-earth elements, and metal elements M creates a composite ferrite structure where metal elements M (particularly Co and Ni) provide high anisotropy and coercive force, while rare-earth elements provide high saturation magnetization. This composite structure achieves both high Br and high resistance to demagnetization.
Data Source
AI summary
The magnet is a ferrite sintered magnet containing a ferrite phase having a magnetoplumbite-type crystal structure. The ferrite sintered magnet contains at least Ca, a metal element A, a metal element R, Bi, Fe, and a metal element M. The metal element A is at least one kind of element selected from the group consisting of Sr, Ba, and Pb, the metal element R is at least one kind of element selected from the group consisting of rare-earth elements including Y and essentially includes La, the metal element M is at least one kind of element selected from the group consisting of Co, Ni, Zn, Al, Cu, and Cr, and essentially includes Co, and when an atonic ratio of the metal elements is expressed by Formula (1), c, a, r, b, f, and m in Formula (1) satisfy the following Expressions (2) to (8).