Solid solubility in 1:13 phase of doping element for La(Fe,Si)13 alloys

Abstract

The influences of Ni, Cr and Nb as substitution elements for Fe were investigated. The change in microstructure and the magnetic properties have been discussed in detail. Substitution elements Ni, Cr and Nb not only have limited solubility in NaZn13-type (1:13) phase, but also hinder the peritectoid reaction. Ni element mainly enters into La-rich phase while Cr element mainly concentrates in α-Fe phase, which both have detriment effect on the peritectoid reaction, leading to a large residual of impurity phases after annealing and a decrease of magnetic entropy change. Besides, Ni and Cr participated in peritectoid reaction by entering parent phases but slightly entering 1:13 phase, which would cause the disappearance of first order magnetic phase transition. A new phase (Fe,Si)2Nb was found when Nb element substitutes Fe in La(Fe,Si)13, suggesting that Nb does not participate in peritectoid reaction and only exists in (Fe,Si)2Nb phase after annealing. The alloy with Nb substitution maintains the first order magnetic phase transition character.

The influence of Cr and Ni on the character of magnetic phase transition in LaFe11.52-xMxSi1.48 alloys

“…It is notes that the solubility of Cr in 1:13 phase is always lower than that in α-Fe, indicating that Cr element is more inclined to enter α-Fe phase, which is consistent with prior paper. 10 And the real content of Cr in 1:13 phase for FOMT LaFe 11.37 Cr 0.15 Si 1.48 and that in 1:13 phase for SOMT LaFe 11.27 Cr 0.25 Si 1.48 is 1.16at%(x=0.18, normalized by La) and 1.81at%(x=0.28), respectively. The real content of Si in main phase (1:13 phase) for LaFe 11.52-x M x Si 1.48 (M=Cr/Ni) increases with the increase of content of M, shown in Fig.…”

“…2 The effect of Cr and Ni element substitution for Fe on the magnetocaloric effect has been studied. [8][9][10] The negative lattice expansion was observed in LaFe 11.14-x Co 0.66 Ni x Si 1.2 alloys. 8 Partial substitution of Ni for Fe in La(Fe 1-x Ni x ) 11.5 Si 1.5 alloys promote fining of the as-cast microstructure and the Curie temperature of La(Fe 1-x Ni x ) 11.5 Si 1.5 alloys increase with the increase of Ni.…”

“…9 Ni and Cr participated in peritectoid and slightly entered in 1:13 phase, which would cause the disappearance of first order magnetic phase transition. 10 In order to further understand the change of the nature of magnetic phase transition by element substitution, present paper investigated the phase formation, composition and magnetic properties for LaFe 11 Ni, 99.999% for Si. An excessive 12wt% of La element was added for the evaporation loss of La during the melting.…”

The role of Ni in modifying the order of the phase transition of La(Fe,Ni,Si)13

“…The dark spots corresponding to α-Fe phase become more noticeable with increasing Ni concentration for higher Ni contents (x=0.3 and 0.4), although the high amount of the obtained 1:13 phase with compositions close to the nominal shows an extension of the solid solubility limit previously ascribed to Ni 47 . In addition, the compositional analysis by EDX (Table 1)…”

Effect of Yttrium on Microstructure and Magnetocaloric Properties in La1−xYxFe11.5Si1.5 Compounds

“…Ni, Cr, and Nb additions had limited solubility in the 1:13 phase. Higher contents of the additions caused a large residual of impure phases after annealing, and a decrease of magnetic entropy change [13,14]. The substitution of rare earth Ce and Pr for La resulted in the enhancement of the magnetic entropy change.…”