Synthesis of Nd₂Fe₁₄B powders by spray-drying and reduction–diffusion processes

The magnetic Nd–Fe–B powders were prepared by a mechanochemical method, including the processes of spray drying, debinding, milling, H₂ reduction, Ca reduction, and washing. The liquid solution dissolved with various metal salts was first spray-dried to prepare the precursor powders having uniformly dispersed Nd, Fe, and B components. The precursor powders in turn were subjected to the subsequent processes. The particle size of the resultant Nd–Fe–B powders was about 1 μm. Effects of the process parameters on phases, morphologies, microstructures, compositions, and thermal properties of the powders were investigated.