Study on the Increase of Co Concentration and the Purification of La–Co Cosubstituted M-Type Sr Ferrite by Oxygen Partial Pressure Control

抄録

The La–Co cosubstituted M-type strontium ferrite attracts attention as a base material for high-performance ferrite magnets. It is known that the uniaxial magnetic anisotropy of the material is enhanced by increasing the amount of Co by heat treatment under high oxygen pressure, but there is a problem in obtaining a pure sample. The present study investigated the conditions to obtain a single phase with increased La–Co substitution by heat treatments under several oxygen pressures. A single phase of M-type ferrite was obtained up to x = 0.35 at p_O2 = 1 atm, and up to x = 0.65 at p_O2 = 10 atm with the composition formula of Sr_1−xLa_xFe_12−xCo_xO₁₉. The magnetic anisotropy is enhanced according to the Co concentration in these samples.

 

This Paper was Originally Published in Japanese in J. Jpn. Soc. Powder Powder Metallurgy 69 (2022) 288–292.

Fig. 6 La (x) and Co (y) compositions determined by WDX for the cases with x_nom = y_nom. Dashed line represents the relation of x = y. SP and MP represent single-phase and multi-phase samples judged from XRD patterns, respectively. Points below the dashed line indicate the presence of Fe²⁺ appeared to compensate the extra-charge due to the substitution of La³⁺ for Sr²⁺.