Journal of Alloys and Compounds, 190 (1992) 69-72 69 JALCOM 401 Ferromagnetic phases in Pr-Nd-Fe Augusto C. Neiva Instituto de Fisica, Universidade de Sdo Paulo, CP 20516, S6o Paulo, S.P. (Brazil) Fernando J. G. Landgraf Instituto de Pesquisas Tecnol6gicas do Estado de Sdo Paulo, CP 7141, S6o Paulo, S.P. (Brazil) Frank P. Missell Instituto de Fisica, Universidade de S~o Paulo, CP 20516, Stio Paulo, S.P. (Brazil) (Received March 31, 1992; in final form June 29, 1992) Abstract Ferromagnetic phases in Pr-Fe and Pr-Nd-Fe were investigated by energy-dispersive X-ray analysis, optical metallography and magnetic measurements. The Pr-Fe phase analogous to NdsFe17 was not obtained. In Pr-Nd-Fe alloys, samples with higher Pr:Nd ratios have slower formation rates for (Pr, Nd)sFe17. I. Introduction As-cast Pr-Fe samples are known to show high coercivities. High coercivities are also reported for PrFeB magnets. Since these systems are closely related to Nd-Fe and Nd-Fe-B, the recent discovery of Nd5Fe17 and the metastable A1 phases in Nd-Fe [1-8] and of the important role played by A1 in NdFeB magnets [3, 4] has stimulated interest in the study of new phases in Pr-Fe and Pr-Fe-B. Furthermore, the production of praseodymium or (Nd,Pr)-based magnets by hot pressing [9], hot rolling [10] or die upsetting [11] has shown the importance of minority phases in determining the coercivity. For Nd-Fe a revised phase diagram was recently presented with the new NdsFe17 phase, formed peri- tectically between 770 and 795 °C [5], with hexagonal symmetry P63/mcm [6]. This phase, with Curie tem- perature Tc = 230 °C, previously referred to as A2 by Schneider and coworkers [5-7], is formed from the metastable A1 phase after relatively short anneals and from Nd2Fe~7 after long anneals. The Pr-Fe system was first studied by Ray [12], who proposed the existence of two intermetallic compounds: Pr2Fe~7 and another peritectic phase tentatively de- scribed as PrFe2. Two metastable phases were reported by Cabral and coworkers [2, 8]. The first, herein called A~, with Tc = 222 °C, is observed in as-cast samples. The second, with Tc = 240 °C, was reported to be found in as-cast [2] materials and in samples annealed for short times at 600 °C [2, 8]. Two phases were also observed by Sfinchez et al. [13] in as-cast samples. The first one, A1, was found to have Tc = 225 °C in samples with 15-40 at.% Fe and lower Tc values down to 182 °C in samples with 2.5 at.% Fe. The second one, observed in binary samples with 22.5-27.5 at.% Fe, was reported to have Tc = 200 °C. In the present work Pr-Fe and Pr-Nd-Fe magnetic and microstructure results are analysed and compared with previous data on Pr-Fe and Nd-Fe. 2. Experiment Binary Pr-Fe samples with 2.5-40 at.% Fe and ternary Pr-Nd-Fe samples were arc melted under pure argon from 99.9% Pr, 99.9% Nd and 99.98% Fe. Annealing treatments were performed in quartz ampoules filled with pure argon, and finalized by water quenching. Magnetic measurements were performed with a vi- brating sample magnetometer. The Curie temperatures Tc were obtained by the "kink point method". Their values were taken at the minima of numerically cal- culated dM/dTvs. T curves [3]. The quoted uncertainties correspond to the width of the dM/dT vs. T curves at half the minimum value. The coercive fields Hc were taken at the maxima of numerically calculated dM/d/-/ vs. H (irreversible susceptibility) curves. The samples were also analysed by energy-dispersive X-ray analysis (EDXA) in a Cambridge Stereoscan 240 scanning elec- tron microscope and by optical metallography. 0925-8388/92/$5.00 © 1992 - Elsevier Sequoia. All rights reserved