Magnetic properties and microstructure of Ti-doped Sm-Fe-N synthesized by reduction diffusion process

•Ti substitution is very effective in particle refinement of Sm2(Fe, Ti)17.•The highest coercivity was achieved in Sm2(Fe, Ti)17N3 magnetic powder with a Ti/Fe mole ratio of 0.04.•The phase stability is influenced by the synergistic effect of Ti substitution atoms and interstitial N atoms. Iron-rich intermetallic compound Sm2Fe17N3 is considered to be a highly promising candidate for new-generation permanent magnetic materials. Here, the Ti-substituted Sm2(Fe, Ti)17N3 alloys were synthesized using reduction-diffusion and nitridation. The microstructure and magnetic properties of Sm2(Fe, Ti)17 and its nitrides, in relation to the effect of Ti substitution, were systematically investigated through a comprehensive experimental approach combined with first-principles calculations. It was revealed that the Ti substitution is very effective in particle refinement of Sm2(Fe, Ti)17. The Rietveld analysis of X-ray data demonstrated an expansion in the unit cell volume of Sm2(Fe, Ti)17 phase with increasing Ti content. Subsequent nitridation experiments highlighted the beneficial impact of an appropriate Ti addition on the enhancement of both coercivity and remanence in Sm2(Fe, Ti)17N3 magnetic powder. The highest coercivity of 8.9 kOe was achieved in the sample with a Ti/Fe mole ratio of 0.04. Furthermore, the possible crystallographic occupancy of Ti and its effect on the phase stability are investigated using first-principles calculations. Our results indicated that the phase stability is influenced by the synergistic effect of Ti substitution atoms and interstitial N atoms. The significance of this study lies in its implications for the development of advanced permanent magnetic materials through reduction-diffusion technology.