The electrochemical behavior of tantalum in the form of K2TaF7 in an LiF-NaF-KF eutectic melt has been studied by linear voltammetry in the temperature range of 560 to 815-degrees-C with and without additions of Na2O. An amperometric titration has been performed by measuring the heights of the cathodic and the anodic peaks. It was shown that at a molar ratio Na2O/K2TaF7 = 1 the predominating complex in the melt is TaOF5(2-), whereas with an Na2O/K2TaF7 molar ratio of 2 it is TaO2F(x)(x-1-), probably in the form of TaO2F4(3-). Increase in the Na2O/K2TaF7 molar ratio in excess of two leads to a decrease of tantalum concentration in the melt, and precipitation of KTaO3 occurs. Both the fluoro complex and the monooxofluoro complex were reduced to metal in a single five-electron step. The fluoro complexes, in the temperature range 625 to 815-degrees-C with potential scan rates 0.5 V . s-1 they discharge irreversibly. Monooxofluoro complexes discharge irreversibly at all temperatures and scan rates studied. The diffusion coefficient of the tantalum fluoro complex depends on the temperature as log D = -2.55 - 2044/T with an activation energy of 39.1 kJ . mol-1. For the tantalum monooxofluoro complex the dependence is log D = -2.35 - 2293/T with an activation energy of 43.9 kJ . mol-1.
展开▼
机译：已经通过线性伏安法在560至815摄氏度的温度范围内（无论是否添加Na2O）研究了LiF-NaF-KF共晶熔体中K2TaF7形式的钽的电化学行为。通过测量阴极和阳极峰的高度进行了安培滴定。结果表明，在摩尔比Na2O / K2TaF7 = 1时，熔体中的主要配合物为TaOF5（2-），而在Na2O / K2TaF7摩尔比为2的情况下，可能是TaO2F（x）（x-1-）。呈TaO2F4（3-）的形式。 Na 2 O / K 2 TaF 7摩尔比的增加超过两个导致熔体中钽浓度的降低，并且发生KTaO 3的沉淀。氟络合物和单氧氟络合物都可以在一个五电子步骤中还原为金属。含氟络合物，温度范围为625至815摄氏度，电势扫描速率为0.5 V。 s-1它们不可逆地放电。一氧化氟络合物在所研究的所有温度和扫描速率下均不可逆地放电。氟钽络合物的扩散系数取决于温度，log D = -2.55-2044 / T，活化能为39.1 kJ。 mol-1。对于单氟氟钽络合物，依赖性为log D = -2.35-2293 / T，活化能为43.9 kJ。 mol-1。
展开▼
