Influence of the presence of Co on the rare earth solubility in M-type hexaferrite powders

Sr _1-xRE _xFe ₁₂O ₁₉ and Sr _1-xRE _xFe _12-xCo _xO ₁₉ ( x=0-0.4 and RE=Pr, Nd) M-type hexaferrite powders were produced according to a conventional ceramic process. The X-ray diffraction analysis of the calcinated material reveals the presence of secondary α-Fe ₂O ₃, PrFeO ₃ or NdFeO ₃ and CoFe ₂O ₄ phases in substituted samples, with proportions that increase with x. However, for the same x value, the proportion of secondary phases is lower in Co-containing powders than in Co-free powders. This indicates that the presence of Co in the M-type phase increases the solubility of the rare earth. The results of the Mössbauer investigation indicate that the solubility of Pr is higher than that of Nd in Co-containing samples.