Preparation of capacitor tantalum powder by magnesiothermic reduction of Ta2O5 assisted by CaCl2 molten salt

Tantalum powder is the core material in tantalum capacitors. However, the traditional magnesium reduction method has problems, such as a high oxygen content and a large number of by-products. This paper proposes a new thermal reduction process for magnesium assisted by molten CaCl₂. With the addition of CaCl₂, the generation of Mg₄Ta₂O₉ is effectively inhibited, resulting in low-oxygen tantalum powder with a uniform coral-like porous structure. The effects of the CaCl₂ addition amount, magnesium dosage, and temperature were systematically investigated. Combined with the orthogonal experiments, the optimal process conditions for preparation were determined. The obtained tantalum powder has an oxygen content as low as 0.35 wt%, and an amorphous oxide layer of 3 nm is formed on the surface. This study provides a new technical route for the preparation of high-performance Ta powder.