Synthesis of Rare Earth Element-Iron-Oxygen Ultrafine Particles by Using Inductively Coupled Plasma

Relation between Ionic Radius of Rare Earth Element and Products

Abstract

We synthesized ultrafine particles in R (rare earth element)-Fe-O systems by a thermal plasma evaporation method. Amorphous citrate gel powders containing R (R=Y, Yb, Er, Ho, Dy, Gd, Eu, Sm and Nd) and Fe were supplied to rf Ar-O₂ thermal plasmas. In the cases of R=Y, Yb, Er, Ho, Dy, Gd and Eu, the synthesized ultrafine particles contained new compounds of RFe_(3+x)O_1.5(4+x). RFe_(3+x) O_1.5(4+x) were synthesized when R ionic radius was smaller than 0.0947nm (that of Eu). The accurate cubic lattice constants of RFe_(3+x)O_1.5(4+x) were calculated from 2θ of the maximum XRD peak (111). In the case of Eu, the lattice constant was at maximum (=0.4866nm). Synthesis of other products such as h-RFeO₃, ε-Fe₂O₃ or γ-Fe₂O₃ were also dependent on R ionic radius. γ-Fe₂O₃ enhanced the saturated magnetization values of ultrafine particles at room temperature. However, γ-Fe₂O₃ did not have such an effect.