Thermostability and magnetic properties of Sm-2(Fe,M)(17)(C,N)(y) (M = Ga,Al and Si)

The effect of heat treatments on the interstitial nitrides and carbides pre pared from Sm-2(Fe,M)(17) and Sm2Fe15Ga2C2 by gas-solid reaction (GSR) was investigated in order to understand more about the influence of the substit utions M = Ga, Al and Si on the thermostability of these compounds. X-ray d iffraction measurements of the heat-treated samples have shown that all of these substitutions improve the thermostability of the Th2Zn17-type interst itial structure, with Al having the smallest influence and Si and Ga having a stronger influence on the thermostability. Contrary to the nitrides, the carbides prepared by GSR can be significantly stabilized with an increasin g amount of the stabilizing elements. Already for a small amount of the sub stitution element, e.g. Sm2Fe16.5Ga0.5, the 2 : 17-type interstitial phase was stabilized up to 750 degrees C. Carburization at temperatures above 500 degrees C was possible for the stabilized 2 : 17 compounds making possible much shorter carburization times for high C contents. Investigations on Sm 2Fe15Ga2C2 have revealed a dependence of the thermostability on the amount of absorbed C and on the processing route for the interstitial modification by GSR. A coercivity mu(0J)H(c) UP to about 2.8 T was obtained for Sm2Fe15 Ga2C2N showing the magnetic potential of these modified compounds. (C) 1999 Elsevier Science B.V. All rights reserved.