TY - JOUR
T1 - High-Performance Hexaferrite Ceramic Magnets Made from Nanoplatelets of Ferrihydrite by High-Temperature Calcination for Permanent Magnet Applications
AU - Vijayan, Harikrishnan
AU - Laursen, Amalie P.
AU - Stingaciu, Marian
AU - Shyam, Priyank
AU - Gjørup, Frederik H.
AU - Simonsen, Jesper
AU - Christensen, Mogens
N1 - Publisher Copyright:
© 2023 American Chemical Society. All rights reserved.
PY - 2023/5
Y1 - 2023/5
N2 - Highly aligned ceramic hexaferrite magnets with high-energy products (BH)maxand a density exceeding 90% of theoretical density have been fabricated. The precursors were an antiferromagnetic powder, a six-line ferrihydrite mixed with SrCO3, and a grain growth inhibitor SiO2. Conventional cold compaction of the precursor powders was employed prior to calcination at temperatures of 1050, 1150, and 1250 °C. The influence of calcination temperature and magnetic properties has been systematically studied in the produced ceramic magnets. Conventional cold compaction is a favorable route for industrial production when compared with other compaction techniques like spark plasma sintering, hot compaction, or electroforging. A high (BH)maxof 25.2 kJ/m3was obtained for the best magnet along with an appreciable coercivity, Hc, of 187 kA m-1, a high squareness ratio, Mr/Ms, of 0.84, and a saturation magnetization, Ms, of 73 A m2/kg. Texture and crystallite size analysis were extracted from 2D synchrotron transmission powder diffraction measurements. We have demonstrated that high-performance bulk magnets for permanent magnet applications can be produced from nonmagnetic interacting crystallites mixed with a grain growth inhibitor without applying a magnetic field for alignment.
AB - Highly aligned ceramic hexaferrite magnets with high-energy products (BH)maxand a density exceeding 90% of theoretical density have been fabricated. The precursors were an antiferromagnetic powder, a six-line ferrihydrite mixed with SrCO3, and a grain growth inhibitor SiO2. Conventional cold compaction of the precursor powders was employed prior to calcination at temperatures of 1050, 1150, and 1250 °C. The influence of calcination temperature and magnetic properties has been systematically studied in the produced ceramic magnets. Conventional cold compaction is a favorable route for industrial production when compared with other compaction techniques like spark plasma sintering, hot compaction, or electroforging. A high (BH)maxof 25.2 kJ/m3was obtained for the best magnet along with an appreciable coercivity, Hc, of 187 kA m-1, a high squareness ratio, Mr/Ms, of 0.84, and a saturation magnetization, Ms, of 73 A m2/kg. Texture and crystallite size analysis were extracted from 2D synchrotron transmission powder diffraction measurements. We have demonstrated that high-performance bulk magnets for permanent magnet applications can be produced from nonmagnetic interacting crystallites mixed with a grain growth inhibitor without applying a magnetic field for alignment.
KW - ceramic magnets
KW - cold compaction
KW - crystallite size
KW - six-line ferrihydrite
KW - texture
UR - http://www.scopus.com/inward/record.url?scp=85161045453&partnerID=8YFLogxK
U2 - 10.1021/acsanm.2c05227
DO - 10.1021/acsanm.2c05227
M3 - Journal article
AN - SCOPUS:85161045453
SN - 2574-0970
VL - 6
SP - 8156
EP - 8167
JO - ACS Applied Nano Materials
JF - ACS Applied Nano Materials
IS - 10
ER -