Mechanochemical Synthesis and Characterization of Nanostructured ErB₄ and NdB₄ Rare‐Earth Tetraborides

Rare‐earth borides have become very popular in recent decades with high mechanical strength, melting point, good corrosion, wear, and magnetic behavior. However, the production of these borides is very challenging and unique. The production of ErB 4 and NdB 4 nanopowders via mechanochemical synthesis (MCS) is reported in this study first time in the literature. Er 2 O 3 or Nd 2 O 3 , B 2 O 3 , and Mg initial powders are mechanically alloyed for different milling times to optimize the process. Rare‐earth borides with MgO phases are synthesized, then MgO is removed with HCl acid. The nanostructured rare‐earth tetraboride powders are analyzed using X‐ray diffraction (XRD). Based on the XRD, ErB 4 powders are produced successfully at the end of the 5 h milling. However, the NdB 4 phase does not occur as the stoichiometric ratio, so the B 2 O 3 amount is decreased to nearly 35 wt%. When the amount of B 2 O 3 is decreased to 20 wt%, NdB 4 and NdB 6 phases are 50:50 according to the Rietveld analysis. However, a homogenous NdB 4 phase is obtained with 30 wt% loss of B 2 O 3 . The average particle sizes of ErB 4 and NdB 4 powders are nearly 100.4 and 85.6 nm, respectively. The rare‐earth tetraborides exhibit antiferromagnetic‐to‐paramagnetic‐like phase transitions at 18 and 8.53 K, respectively.