Study on the microstructure and magnetic properties of Sm-Fe-Ti alloys and their nitrides

Sm2Fe17-xTixN compounds were prepared from the starting Sm2Fe17-xTix alloy by nitrogenation processes for 2, 4, 6 and 10 h. The microstructure and crystal lattice parameters of the Sm2Fe17-xTixN system were presented in detail. The main phase of all Sm2Fe17-xTixN (with x = 0, 0.5, 1.0 and 2.0) compounds behave the Th2Zn17-type structure, tiny alpha-Fe, SmFe2, FeTi, Fe2Ti phases may coexist. Ti dissolves into three different phases: Sm-2(Fe,Ti)(17), FexTi and alpha-Fe(Ti). With increasing Ti content, corresponding characteristic peaks of Sm2Fe17-xTix shift to lower angles and the increment (DeltaV/V) of unit cell volume for Sm2Fe15Ti2 were increased up to 3.898%. However, the deviation amplitude Delta2theta for the same sample was nearly not changed with the increasing of 2theta angle from 20degrees to 70degrees. For the same Sm2Fe17-xTix, corresponding characteristic peaks of Sm2Fe17-xTixN also shift to lower angles with the increasing of nitriding time. Furthermore, Delta2theta for high angles was more negative than that for lower angles. Delta2theta of samples with high Ti content was more negative than that with low Ti content when nitrogenized for less than 6 h, but Delta2theta of corresponding peaks for all Sm2Fe17-xTixN samples behaved in the same way when nitrogenated for over 6 h. The maximum Delta2theta deviation value at 2theta = 70degrees was over 2.2degrees after being nitrogenated for 10 h. The maximum lattice parameters, a = 8.82 Angstrom(2), c = 12.88Angstrom, V = 868Angstrom(3), and DeltaV/V = 10.19% were obtained, but c/a = 1.45 was not changed. The saturation magnetization value of all Sm2Fe17-xTixN were limited in the scope of 88-1100 kA/m, so the saturation magnetization was not obviously improved for the Ti substitution for some Fe atoms in this alloy. (C) 2004 Elsevier B.V. All rights reserved.