Abstract
The electrochemical behavior of molten salts systems where LiCl, NaCl, NaCl-KCl, KCl and CsCl were used as solvent for K2TaF7 and K3TaOF6 was investigated. In particular, the influence of the electrolysis parameters, such as concentration of tantalum species in electrolyte, temperature and current density on the cathodic products phase composition was determined by X-ray diffraction and scanning electron microscopy. Several phases generally crystallized at the cathode simultaneously. Among identified phases were metallic tantalum in cubic (α) and tetragonal (β) crystal modifications, tantalum oxide bronzes (hexagonal, tetragonal, cubic) and TaO. The most characteristic phases for the CsCl melt were two isostructural compounds with pyrochlor type crystal lattice CsTa52+zO5+yF1- y and CsTa5-x2+zO5+yF1-y. The former deposited in the form of transparent dielectric crystals and the later - in the form of metal-like conductive ones. This latter compound seems to be synthesized for the first time.