X-RAY STRUCTURAL STUDIES OF NITROGEN DIFFUSION IN DY2FE17

The reaction between N-2 and Dy2Fe17 has been studied by thermopiezic analysis on 20-25 mu m sized powders in the temperature range 400-500 degrees C. Partially nitrided powders were analyzed using CuKalpha x-r ay diffraction and thermomagnetic techniques. Both high angle x-ray an d thermomagnetic data show only the presence of Dy2Fe17 and DY2Fe17N3- delta (delta<0.3) With no evidence of intermediate compositions. The r esults of the x-ray diffraction experiments at several Bragg peaks wer e simulated using a two phase model structure: a Dy2Fe17 core with a D y2Fe17N3 surface layer. The results show that at low temperatures the nitride layer is too thin to account for all of the nitrogen absorbed by the sample, indicating that a significant amount of the nitrogen di ffused into the core of the particles, presumably along grain boundari es.