Journal of Magnetism and Magnetic Materials 270 (2004) 291–297 The effect of praseodymium content on the microstructure and magnetic properties of PrFeCoBNb HDDR magnets L.P. Barbosa, H. Takiishi, R.N. Faria* Instituto de Pesquisas Energeticas e Nucleares, IPEN-CNEN, Sao Paulo 05508900, Brazil Received 22 July 2003; received in revised form 19 August 2003 Abstract Thispaperreportstheresultsofinvestigationscarriedouttodeterminethemicrostructureandmagneticpropertiesof some Pr-based magnets represented by the formula Pr x Fe 77.9x Co 16 B 6 Nb 0.1 . Bonded magnets were prepared from cast and homogenized alloys using the hydrogenation, disproportionation, desorption and recombination process. The influence of Pr content on the magnetic properties of these magnets was studied. Praseodymium content has a significant influence on the magnetic behaviour of these magnets. Examination of the microstructures of the magnets revealed that the shape of the magnetic grains (o1 mm) changed with praseodymium content. r 2003 Elsevier B.V. All rights reserved. PACS: 71.20.Eh Keywords: Pr-based alloys; Magnetic materials; Hydrides; Magnetic properties 1. Introduction The hydrogenation, disproportionation, desorp- tion and recombination (HDDR) process has been successfully employed to produce neodymium- based bonded magnets (examples in Refs. [1–4]). In the past, magnetic Pr 13 Fe 81 B 6 powders were produced via the HDDR process, but with inferior magnetic properties, compared to substituted (Pr 1x Nd x ) 13 Fe 81 B 6 materials [5]. Furthermore, the production of Pr 13 Fe 55.9 Co 24 B 6 Ga 1 Zr 0.1 HDDR powders with good remanence was also reported, but the coercivities were still quite poor [6]. Recently, it was shown that anisotropic powders based on the composition Pr 13.7 Fe 63.5 - Co 16.7 B 6 Nb 0.1 , with good remanence and coerciv- ity (B r Em oi H c E1T), can be produced by this process [7–11]. More recently, the effects of cobalt content on the magnetic properties and micro- structure of Pr 14 Fe 79.9x Co x B 6 Nb 0.1 HDDR mag- nets have also been shown [12]. This article reports the results of further investigations carried out on Pr x Fe 77.9x Co 16 B 6 Nb 0.1 -type alloys (x ¼ 12:0; 12.5, 13.0, 13.5, 14.0). This study was undertaken to optimise the praseodymium content with respect to magnetic properties of HDDR permanent magnets. Cobalt- and niobium-free alloys have also been included in this study for comparison. The micro- structures of the HDDR materials were observed with a scanning electron microscope (SEM). ARTICLE IN PRESS *Corresponding author. Tel.: 011-38169345; fax: 011- 38169370. E-mail address: luzinete@ipen.br (R.N. Faria). 0304-8853/$-see front matter r 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.jmmm.2003.08.026