Pr₂Fe₁₄C Permanent Magnet Synthesized By Mechanochemical Method

In this paper,the mechanochemical synthesis of Pr₂Fe₁₄C permanent magnet material,namely high energy ball milling in heptane and annealing under vacuum is reported.The effect of the preparation conditions on the permanent magnetic properties are investigated.Detailed research work are as following:1.Being high energy ball milled in heptane,the PrFe₅ alloy(containing mainly PrFe₁₇ and Pr)disproportionates into PrH_2+? and ?-Fe.Subsequently annealed from room temperature to 850 °C under vacuum,H₂ is released during two temperature ranges and magnetically hard Pr₂Fe₁₄C,along with magnetically soft PrFe₁₇ and ?-Fe,as well as no magnetic Pr-C phases are formed,making the appearance of step in the hysteresis curves at H=0.H and C atoms come from heptane.With the increase of ball milling time t,PrFe₁₇ lessens due to the disproportioantion reaction and the amount of Pr₂Fe₁₄C increases,improving the permanent magnetic properties.Thereafter the amount of ?-Fe increase abruptly,making the decrease of the permanent magnetic properties again.Maximum?BH?max of 1.8MGOe is obtained in sample ball milled for 4 h.2.B is added into PrFe₅ alloy and the permanent magnetic properties is improved obviously.The?BH?max of PrFe₅B_0.05 and PrFe₅B_0.1,balling milled for optimum time,are 6.95 and 7.5 MGOe,respectively?It is the addition of B that promotes the formation of Pr₂Fe₁₄C and suppress the formation of Pr-C phase,increasing the permanent magnetic properties.While too much B will decreases the coercivity value.3.Increasing the Pr:Fe to 1:4 and preserving the amount of B to 0.05,the magnetically soft phases in the sample ball milled for optimum time are decreased further and the squareness of the demagnetization curves are improved obviously,increasing the?BH?max value to 8.5MGOe,though the increase of Pr increase the amount of non magnetic Pr-C phase.