The evolution of lamellar phase and its effect on high temperature magnetic properties in Lu-doped Sm2Co17-type magnets

Abstract

As a diffusion channel for Cu, the lamellar phase significantly influences the magnetic properties of Sm₂Co₁₇-type magnets, but its formation process remains unclear. In this paper, the impact of Lu substitution on Sm₂Co₁₇-type magnets was investigated. The inclusion of Lu was observed to significantly facilitate an increase in the 2:17R' phase within the solid solution. The increased 2:17R' phase leads to a rapid precipitation of the lamellar phase during aging treatment, as the ABBA-type atomic layer stacking structure promotes the formation of a 1:3R phase. Furthermore, the premature formation of the 1:3R phase inhibits subsequent continuous precipitation of the cell boundary phase, leading to a decrease in coercivity. However, the Cu content in cell boundary phase increases, optimizing the coercivity temperature coefficient from -0.17 %/ °C to -0.15 %/ °C between RT and 823 K. Our elucidation of the lamellar phase formation provides novel insights for optimizing the high-temperature magnetic performance of Sm₂Co₁₇-type magnets.