scholarly journals Nd-Fe-B Magnets: The Gradient Change of Microstructures and the Diffusion Principle after Grain Boundary Diffusion Process

Materials ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 3881 ◽  
Author(s):  
Yaojun Lu ◽  
Shuwei Zhong ◽  
Munan Yang ◽  
Chunming Wang ◽  
Liuyimei Yang ◽  
...  
Keyword(s):  
Surface Layer ◽  
Grain Boundary ◽  
Diffusion Process ◽  
Shell Structure ◽  
Boundary Diffusion ◽  
Diffusion Mechanism ◽  
Temperature Stability ◽  
Grain Boundary Diffusion ◽  
Core Shell ◽  
Core Shell Structure

The diffusion of Tb in sintered Nd-Fe-B magnets by the grain boundary diffusion process can significantly enhance coercivity. However, due to the influence of microstructures at different depths, the coercivity increment and temperature stability gradually decreases with the increase of diffusion depth, and exhibit good corrosion resistance at a sub-surface layer (300–1000 μm). According to the Electron Probe Micro-analyzer (EPMA) test results and the diffusion mechanism, the grain boundary and intragranular diffusion behavior under different Tb concentration gradients were analyzed, and the diffusion was divided into three stages. The first stage is located on the surface of the magnet, which formed a thick core-shell structure and a large number of RE-rich phases. The second stage is located in the sub-surface layer, forming a uniform and continuous RE-rich phase and thin core-shell structure. The third stage is located deeper in the magnet, and the Tb enrichment only existed at the triangular grain boundary.

scholarly journals Optimized Microstructure and Improved Magnetic Properties of Pr-Dy-Al-Ga Diffused Sintered Nd-Fe-B Magnets

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2583
Author(s):  
Pengpeng Qu ◽  
Feifei Li ◽  
Sajjad Ur Rehman ◽  
Lei He ◽  
Xiaoqiang Yu ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Magnetic Properties ◽  
Rare Earth ◽  
Grain Boundary ◽  
Diffusion Process ◽  
Boundary Diffusion ◽  
Grain Boundary Diffusion ◽  
Shell Structures ◽  
Core Shell ◽  
Thermal Stability Of

The grain boundary diffusion process (GBDP) has become an important technique in improving the coercivity and thermal stability of Dy-free sintered Nd-Fe-B magnets. The influence of Dy70Al10Ga20 and (Pr75Dy25)70Al10Ga20 alloys by the GBDP on sintered Nd-Fe-B magnets are investigated in this paper. After diffusing Dy70Al10Ga20 and (Pr75Dy25)70Al10Ga20 alloys, the coercivity (Hcj) of the magnets increased from 13.58 kOe to 20.10 kOe and 18.11 kOe, respectively. Meanwhile, the remanence of the magnets decreased slightly. The thermal stability of the diffused magnets was improved by the GBDP. The microstructure shows continuous Rare-earth-rich (RE-rich) grain boundary phases and (Dy, Pr/Nd)2Fe14B core-shell structures which contribute to improving the coercivity. Moreover, the Dy concentration on the surface of the (Pr75Dy25)70Al10Ga20 diffused magnets decreased with the Pr substitution for the Dy element. The openness of the recoil loops for the (Pr75Dy25)70Al10Ga20 diffused magnets is smaller than that of the original magnets and Dy70Al10Ga20 diffused magnets. The results show that the (Pr75Dy25)70Al10Ga20 alloys can effectively optimize the microstructure and improve the magnetic properties and thermal stability of the sintered Nd-Fe-B magnets.

Coercivity Enhancement of Nd-Fe-B HDDR Powder by Grain Boundary Diffusion Process with Rare-Earth Hydride

JOM ◽  
2018 ◽  
Vol 70 (5) ◽  
pp. 661-665 ◽  
Author(s):  
Hee-Ryoung Cha ◽  
Jae-Gyeong Yoo ◽  
Youn-Kyoung Baek ◽  
Dong-Hwan Kim ◽  
Hae-Woong Kwon ◽  
...  
Keyword(s):  
Rare Earth ◽  
Grain Boundary ◽  
Diffusion Process ◽  
Boundary Diffusion ◽  
Grain Boundary Diffusion

scholarly journals Coercivity enhancement in heavy rare earth-free NdFeB magnets by grain boundary diffusion process

2018 ◽  
Vol 113 (15) ◽  
pp. 152402 ◽  
Author(s):  
D. Salazar ◽  
A. Martín-Cid ◽  
R. Madugundo ◽  
J. M. Barandiaran ◽  
G. C. Hadjipanayis
Keyword(s):  
Rare Earth ◽  
Grain Boundary ◽  
Diffusion Process ◽  
Boundary Diffusion ◽  
Grain Boundary Diffusion ◽  
Heavy Rare Earth ◽  
Ndfeb Magnets

Diffusion and solubility of holmium ions in barium titanate ceramics

2004 ◽  
Vol 19 (12) ◽  
pp. 3512-3520 ◽  
Author(s):  
Junichi Itoh ◽  
Hajime Haneda ◽  
Shunichi Hishita ◽  
Isao Sakaguchi ◽  
Naoki Ohashi ◽  
...  
Keyword(s):  
Barium Titanate ◽  
Grain Boundary ◽  
Diffusion Coefficients ◽  
Boundary Diffusion ◽  
Diffusion Mechanism ◽  
Annealed Sample ◽  
Lattice Diffusion ◽  
Grain Boundary Diffusion ◽  
A Site ◽  
Titanate Ceramics

Ho ion solubility and diffusivity were evaluated in barium titanate ceramics in which Ho ions were implanted with an accelerating voltage of 500 keV. The depth profile of the ions was composed of three regions in the post-annealed sample: the first was the precipitation region, the second was a region created by lattice diffusion of Ho ions, and the third was a region created by grain-boundary diffusion. The Ho lattice diffusion characteristics were similar to those of Ni ion diffusion in barium titanate ceramics, and we concluded that the diffusion mechanism was the same as that responsible for Ni ions. The Ho ions diffused through the B-site (Ti-site) and were then exchanged with A-site ions. This mechanism suggests that a small number of Ho ions dissolved in the B-site. Preferential grain-boundary diffusion was also observed. The grain-boundary diffusion coefficients were four to five orders of magnitude larger than the volume diffusion coefficients. The solubility of Ho ions was estimated to be a few thousand parts per million in barium titanate ceramics.

High-coercivity Nd-Fe-B magnets obtained with the electrophoretic deposition of submicron TbF3 followed by the grain-boundary diffusion process

2016 ◽  
Vol 115 ◽  
pp. 278-284 ◽  
Author(s):  
Marko Soderžnik ◽  
Matic Korent ◽  
Kristina Žagar Soderžnik ◽  
Matthias Katter ◽  
Kaan Üstüner ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Diffusion Process ◽  
Electrophoretic Deposition ◽  
Boundary Diffusion ◽  
Grain Boundary Diffusion ◽  
High Coercivity
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