Effect of boron content on the magnetic properties, phase evolution and microstructure of Pr9Fe88.5-xTi2.5Bx (x=7-15) nanocomposites

The effect of boron content on the magnetic properties, phase evolution and the exchange coupling effect of Pr₉Fe_88.5-xTi_2.5B_x ribbons is investigated. By increasing the boron content, the optimal magnetic properties of B_r=9.5 kG, _jH_c=10.8 kOe, and (BH)_max=17.8 MGOe are obtained for Pr₉Fe_bal.Ti_2.5B₁₁. Further substituting 10 at% Co for Fe in the Pr₉Fe_bal.Ti_2.5B₁₁ alloy enhances the magnetic properties for Pr₉Fe_67.5Co₁₀Ti_2.5B₁₁. Based on thermal magnetic analysis of the optimized Pr₉Fe_88.5-xTi_2.5B_x ribbons, three phases Pr₂Fe₁₄B, α-Fe and a small amount of Pr₂Fe₂₃B₃ phases prevailed in the ribbons with x=15. For x=7-13, only Pr₂Fe₁₄B and α-Fe phases were found. Increasing x increases the volume fraction of Pr₂Fe₁₄B phase and decreases the α-Fe phase, giving rise to the increment of _jH_c and the decrement of B_r. But a decrement of the volume fraction of total magnetically phases, i.e. α-Fe and Pr₂Fe₂₃B₃, results in the deterioration of both B_r and (BH)_max drastically as x=15.