Polarography, linear-sweep voltametry and potentiostatic electrolysis were used to investigate the behavior of Ta in the ternary eutectic. It was found that the reduction of Ta occurred in 2 stages. From the kinetics of the first stage, it was deduced that the diffusivity of pentavalent Ta ranged from 7.6 x 10-7 to 2.67 x 10-6cm2/s at temperatures ranging from 831 to 973K. The data could be described by the expression: log [D (cm2/s)] = -2.39 - 3099/T(K)

giving an activation energy of 59.3kJ/mol. It was also found that the diffusivity of quadrivalent Ta was described by the expression:

log [D (cm2/s)] = -4.0 - 1633/T(K)

giving an activation energy of 31.3kJ/mol.

L.P.Polyakova, B.I.Kosilo, E.G.Polyakov, A.B.Smirnov: Elektrokhimiya, 1988, 24[7], 892-7 (Soviet Electrochemistry, 1988, 24[7], 825-30)