Synthesis of LaB ₆ powders from La ₂O ₃, B ₂O ₃ and Mg blends via a mechanochemical route

This study reports a room temperature mechanochemical route for the synthesis of LaB ₆ powders from La ₂O ₃-B ₂O ₃-Mg blends. The synthesis reaction was driven by high-energy ball milling and was gradually examined in terms of milling duration and process control agent. Following the mechanochemical synthesis, unwanted MgO phase and Fe contamination worn off from the milling vial/balls were removed with HCl acid leaching under the effect of ultrasonic stirring. Pure LaB ₆ powders were obtained after repeated centrifuging, repeated washing and drying. Subsequent annealing was performed in a tube furnace at 800 °C for 5 h under Ar atmosphere in order to reveal residual elements. Phase and microstructural characterizations of the milled, leached and annealed powders were performed using X-ray diffractometry (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. A novel route for producing fine-grained LaB ₆ powders was accomplished with shorter reaction times resulting in higher purity.