Phase diagram of the Co-rich Co-Pr-Nd system at 500 °C

Abstract The 500 °C isothermal section of the Co-rich Co–Pr–Nd (Co>40 at.%) system was investigated by X-ray powder diffraction, differential thermal microanalysis (DTA) and electron-probe microanalysis (EPMA) techniques. The result shows that this section consists of eight single-phase regions and seven two-phase regions. The compounds Pr 2 Co 17 and Nd 2 Co 17 , PrCo 5 and NdCo 5 , Pr 5 Co 19 and Nd 5 Co 19 , Pr 2 Co 7 and Nd 2 Co 7 , PrCo 3 and NdCo 3 , PrCo 2 and NdCo 2 , Pr 4 Co 3 and Nd 4 Co 3 form a continuous series of solid solutions, because the corresponding compounds have the same crystal structure, about the same lattice parameters and are of similar character. Solid solubilities of Co in these compounds were not detectable. The e phase was successfully indexed on the basis of a hexagonal lattice with a =5.07A and c =24.48A. We were not able to confirm the existence of the compound Nd 2 Co 3 , and the X-ray diffraction patterns of the alloys near the compositions Pr 2 Co 1.7 , Nd 2 Co 1.7 , Pr 4 Co 3 or Nd 4 Co 3 showed the existence of the compounds Pr 4 Co 3 and Nd 4 Co 3 . The compounds Pr 2 Co 1.7 and Nd 2 Co 1.7 do not exist; they are in fact the compounds Pr 4 Co 3 and Nd 4 Co 3 .