Effect of Si Substitution on Structure and Magnetic Properties in Mischmetal-Fe-B Ribbons

(La_0.35Ce_0.65)₂Fe_14-xSi_xB (x = 0.0, 0.5, 1.0, 1.5, 2.0) ribbons were prepared by the melt-spinning technique, and La-Ce mischmetal with impurities was used as the starting material. The effects of Si substitution on phase formation and room temperature magnetic properties were investigated by X-ray diffraction and a vibrating sample magnetometer. It was found that the optimal wheel velocity dropped dramatically when a small amount of Si was introduced. It dropped from 20 to 15 m/s while Si concentration increased from x = 0.0 to 0.5. We also found that increasing the Si content can damage the phase formation of the 2:14:1 structure, which is different from the case in Nd₂Fe₁₄B and even in Ce₂Fe₁₄B. The substitution of Si for Fe does not enhance the coercivity of (La_0.35Ce_0.65)₂Fe₁₄B magnets effectively. The result indicates that the early findings about the element substitution and addition in Nd₂Fe₁₄B cannot be simply copied in research studies of (La_0.35Ce_0.65)₂Fe₁₄B.