The determination of the microstructure and chemical composition of La0.7-xPr xMg0.3Al 0.3Mn0.4Co0.5 Ni3.8 (0 < x < 0.7) metal hydride alloys has been carried out using scanning electron microscopy (SEM), energy dispersive X ray analysis (EDX) and X ray diffraction analysis (XRD). The substitution of La with Pr changed the grain structure from equiaxial to columnar. The relative atomic ratio of rare earth to (Al, Mn, Co, Ni) in the matrix phase was 1:5 (LaNi5-type structure). Magnesium was detected only in two other phases present. A grey phase revealed 11 at.% Mg and the concentration ratios of other elements indicated the composition to be close to PrMgNi4. A dark phase was very heterogeneous in composition, attributed to the as-cast state of these alloys. The phases identified by XRD analysis in the La0.7Mg0.3Al0.3Mn0.4Co 0.5Ni3.8 alloy were: La(Ni,Co)5, LaAl(Ni,Co)4, La2(Ni,Co)7 and AlMn(Ni,Co)2. Praseodymium favors the formation of a phase with a PuNi3-type structure. Cobalt substituted Ni in the structures and yielded phases of the type: Pr(Ni,Co)5 and Pr(Ni,Co)3.

Microstructures and magnetic properties of Pr-Fe-Co-B bonded magnets were investigated. The magnets can be represented by the formulae, Pr14Fe63.9Co16B6M 0.1 (M = Ti, V, Cr, Ni, Zr, Nb or Mo), Pr14Fe63.8Co16B6Nb 0.1T0.1 (T/= Al, Si, P, Cu or Ga) and Pr14Fe63.6Co16B6Nb 0.1R0.3 (R = Gd, Tb or Dy). The effects of additions on the magnetic properties of PrFeCoB-based magnets have been studied. Magnetically hard powders have been produced from homogenised alloys using the hydrogenation, disproportionation, desorption and recombination (HDDR) process. The HDDR powders were isostatically pressed and bonded with cyanoacrylate adhesive to form permanent magnets.

Sintered Pr-based magnets were produced using a new laboratory technique for powder handling. Unlike the conventional procedure for preparing sintered permanent magnets in the laboratory, the powder technique used in this investigation does not require a glove box. The effects of processing parameters on the magnetic properties of Pr-based sintered magnets prepared using the hydrogen decrepitation process have been studied. Specifically, the effects of sintering temperature and milling time for processing Pr16Fe76B8 magnets have been investigated. Pr16Fe76B8 magnets with the best magnetic properties were sintered between 1015 °C to 1075 °C.