Preparation of tantalum powders via the sodium reduction of potassium heptafluorotantalate heat-treated in air

摘要

Tantalum powders have been prepared by sodium reduction in melts containing potassium heptafluorotantalate (K2TaF7) heat-treated in air. Their specific surface area is three to four times that of powders obtained by reducing unheat-treated K2TaF7 under the same conditions. The increase in specific surface area is due to the reduction of tantalum oxyfluoride complexes (K3TaOF6 and K2TaOF5) and Marignac's salt (K2Ta2O3F6) forming during heat treatment of K2TaF7. Potassium heptafluorotantalate heat-treated at temperatures from 600 to 670A degrees C is shown to be suitable as a starting material for producing high-capacitance tantalum capacitor powder.