Abstract
The phase equilibria of the ternary system Bi-Mn-Sb were experimentally investigated with focus on the possible existence of a ferromagnetic continuous solid solution between α-BiMn and MnSb at 320 °C (both B81, NiAs structure type). Isothermal sections at 320 and 600 °C were studied applying powder x-ray diffraction and scanning electron microscopy including energy dispersive x-ray spectroscopy. The corresponding isothermal sections at 320 and 600 °C were established based on these results. A complete ternary reaction scheme (Scheil diagram) and a liquidus surface projection based on primary crystallization analyses and DTA (differential thermal analysis) were constructed. Furthermore, the vertical section at 10 at.% Sb was studied by DTA. A continuous solid solution between the isostructural phases α-BiMn and MnSb, as reported in the literature, could not be confirmed. A new hexagonal P63/mmc setting of the known orthorhombic P2221 ternary phase BixMnSb1−x, based on single-crystal x-ray diffraction data, is described.
Highlights
An increase in the demand of rare earth elements (REEs), for the production of efficient permanent magnets, will be a major factor for both cost and availability of these elements in the near future
The 320 °C isothermal section, illustrated in Fig. 2, shows the three binary phases a-BiMn, Mn2Sb and MnSb together with the ternary phase * MnBi0.9Sb0.1, designated here by s, but there is no indication whatsoever of a continuous solid solution between a-BiMn and MnSb as it had been found at 250 °C by Dannohl and Gmohling.[11]
In an attempt to stabilize the ferromagnetic phase a-BiMn by the addition of a third element, the ternary Bi-Mn-Sb phase diagram was investigated experimentally
Summary
An increase in the demand of rare earth elements (REEs), for the production of efficient permanent magnets, will be a major factor for both cost and availability of these elements in the near future. Extensive research has been devoted to design ferromagnetic materials free of REEs for more than two decades. A possible approach to circumvent these problems was considered the addition of a third component such as Ni, Pt or Rh, which forms an intermetallic phase with Bi that is iso-typic with a-BiMn.[9,10]. Another promising possibility was the partial substitution of Bi by Sb, which forms two ferromagnetic phases with Mn, i.e. Mn2Sb and MnSb. Of these, hexagonal MnSb is isotypic with a-BiMn; in addition, Bi and Sb are completely miscible with each other. This possibility had been indicated by an early report by Dannohl and Gmohling[11] who found a continuous solid solution between a-BiMn and MnSb at 250 °C
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