Preparation and magnetic properties of high performance Ca–Sr based M-type hexagonal ferrites

• Published in: Results in materials 2020-12, Vol.8, p.100150, Article 100150
• Main Authors: Huang, Ching-Chien, Mo, Chin-Chieh, Hsiao, Tsung-Han, Chen, Guan-Ming, Lu, Sheng-Han, Tai, Yen-Hua, Hsu, Hsiao-Hsuan, Cheng, Chun-Hu
• Format: Article
• Language: English
• Subjects: Ca–Sr based; Hard ferrite; Iron oxide powder (Fe2O3); Motor; Secondary fine-milling; Thermal annealing
• ISSN: 2590-048X; 2590-048X
• DOI: 10.1016/j.rinma.2020.100150

In this study, the preparation and magnetic properties of Ca–Sr M-type (Ca1-x-yLaxSryFe10.9CozO19) ferrire magnets were investigated. A M-type singlephase calcined powder was synthesized with a composition of x ​= ​0.45, y ​= ​0.18 and z ​= ​0. And a very high magnetic properties of Br ​= ​5425Gauss and iHc ​= ​4602Oe were obtained by the thermal annealing and secondary fine-milling method in the sintered magnets. The magnetic properties greats exceeds that of traditional Sr–La–Co M-type ferrite, which has been the highest grade M-type hard ferrite. By use of the innovative post-processing method, the improvement could be attributed to about 4% and 0.8% increase in motor torque and motor efficiency in comparison to that of conventional process, which will eventually be used in high-efficiency motors. •Enhancement in magnetic properties are realized by optimized stoichiometry of Ca–Sr based ferrites without cobalt in calcination.•Strict control of powder size after secondary fine milling promotes grain growth homogeneity in sintering.•Higher magnetic properties of permanent magnet enhance both the motor torque and motor efficiency is demonstrated.•These technologies could be further extended to different grades of hard ferrites applied to various types of energy-efficient motors if an appropriate process condition and the composition of the ferrites were selected.