Novel eco-friendly low cost and energy efficient synthesis of (Nd-Pr-Dy)2Fe14B magnetic powder from monazite concentrate

Abstract

Syntheses of Nd₂Fe₁₄B magnetic powder by conventional method is a complicated multi-step process, which produces harmful pollutants and consumes a huge amount of energy and resources. Herein we report a simple chemical route for the preparation of (Nd-Pr)₂Fe₁₄B magnetic powder using monazite concentrate as a precursor. Th, U, Sm, and La impurities were removed from monazite leachate by roasting, solvent extraction and leaching the concentrate. Purified leachate consisting of Nd and Pr Chlorides was added to the FeCl₃ solution, and the solution produced was co-precipitated with NaOH. RE and Fe hydroxide precipitates were converted to the oxides by annealing at 700 °C. Boric acid and CaH₂ were added in the RE and Fe oxides produced, and this mixture was reduced and diffused to (Nd-Pr)₂Fe₁₄B. Magnetic properties of the (Nd-Pr)₂Fe₁₄B produced were enhanced by introducing antiferromagnetic coupling, induced by Dy addition and efficient removal of CaO byproduct through ball milling in ethanol which increased the BH_max from 3.9 to 11.45 MGOe. Process reported is energy efficient, environment-friendly, time saving and low-cost.