Formation of metastable Pr/sub 2/Fe/sub 23/B/sub 3/ phase and its effect on magnetic properties in rapidly quenched Pr/sub 9/Fe/sub 91-X/B/sub X/ nanocomposites

Zhongmin Chen, B.R. Smith, Bao-Min Ma, Mei-Qing Huang, Ya-Qiao Wu, M.J. Kramer
2003 IEEE transactions on magnetics  
The formation of metastable Pr 2 Fe 23 B 3 phase and its effect on magnetic properties of melt-spun Pr 9 Fe 91 x B x (x = 4-12) have been investigated. Thermogravimetric analysis (TGA) and X-ray diffraction (XRD) studies show that the samples consist of Pr 2 Fe 14 B and -Fe phases at low B content, and Pr 2 Fe 14 B, -Fe and Fe 3 B at high B content. The metastable Pr 2 Fe 23 B 3 phase appears in the intermediate B content (8-12 at%). This metastable Pr 2 Fe 23 B 3 phase results in a poor
more » ... ess in the demagnetization curve and is detrimental to the hard magnetic properties. Transmission electron microscopy (TEM) studies reveal larger average grain sizes when the B content is at 8.5 at% or above. It is further found that this metastable phase can be transformed into Pr 2 Fe 14 B, -Fe, and Fe 3 B by annealing the sample at temperature of 750 C or above, leading to a more square demagnetization curve. However, B r of the nanocomposite decreases slightly due to the excessive grain growth during high-temperature annealing. Index Terms-Metastable phase, nanocomposite magnet, Pr 2 Fe 23 B 3 , rapidly quenching.
doi:10.1109/tmag.2003.815891 fatcat:f4uytxiwwjd4zkdosyf4tjjkxu