NITROGENATION BEHAVIOR AND THERMOSTABILITY OF MECHANICALLY ALLOYED SM12.5FE87.5 NITRIDE

The structural and magnetic properties of mechanically alloyed samples of Sm12.5Fe87.5 have been studied by adjusting the nitrogenation temp erature and time. When the nitrogenation temperature is 500 degrees C, a very short time (less than 5 min) is needed for the nitrogen atoms to be introduced into the lattice. No prominent incubation time is obs erved, consequently the magnetic properties (including the Curie tempe rature) of the samples depend only slightly on the nitrogenation time. When nitrogenated at 260 degrees C, two phases, SmFe7 and SmFe7Ndelta , coexist in the samples. The temperature dependences of the magnetic properties of the Sm-Fe-N magnets have been measured up to 600 degrees C. It is found that Sm-Fe-N. powders as well as polymer-bonded magnet s made by mechanical alloying have a good thermostability. The coerciv ity at 200 degrees C of the Sm-Fe-N magnets is greater than 10 kOe. At 550 degrees C the main phase SmFe7Ndelta decomposes into SmN and alph a-Fe and the magnetic properties of the samples are rapidly degraded.