Intervalence Charge Transfer and Electronic Transport in Molten Salts Containing Tantalum and Niobium Complexes of Mixed Valency.
Intervalence Charge Transfer and Electronic Transport in Molten Salts Containing Tantalum and Niobium Complexes of Mixed Valency.
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DOI：
10.1002/chin.199951008
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发表时间：
1999-12
期刊：
影响因子：
--
通讯作者：
U. Stoehr;W. Freyland
中科院分区：
文献类型：
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作者：
U. Stoehr;W. Freyland
我们报道了在含有不同氧化态的氯化钽或铌和氯氧配合物的碱卤化物熔体中的电子电导率和部分电子迁移率和光吸收光谱的测量。电化学阻抗谱法和Wagner-Hebb极化法在各种氧化还原电位和高达1000 K的温度下被应用。在所有系统中，电子电导率与平衡氧化还原电位的关系都接近抛物线，Ta(IV) -Ta (V)平衡附近的潜潜值最大为σe∽0.1 Ω-1 cm-1，在含铌系统中各氧化还原平衡的潜潜值较低。阻抗实验和极化实验的结果在2倍以内一致。在830 K时，潜到10-2 cm2 s-1的典型值，在830±T/K≤980时，潜到10-2 cm2 s-1的活化能约为0.7 eV。讨论了熔体中电子跳跃和价间电荷转移的一个简单的二元模型，该模型定性地解释了所观察到的电子电导率的抛物线势依赖性及其温度依赖性。
We report measurements of the electronic conductivity and partly the electronic mobility and optical absorption spectra in alkali halide melts containing tantalum or niobium chloride and oxychloride complexes in different oxidation states. Both electrochemical impedance spectroscopy and the Wagner–Hebb polarization method have been employed at various redox potentials and temperatures up to 1000 K. In all systems a nearly parabolic potential dependence of the electronic conductivity around the equilibrium redox potential is observed with a maximum of σe∽0.1 Ω-1 cm-1 near the Ta(IV)–Ta(V) equilibrium and lower values for the respective redox equilibria in the niobium containing systems. Results from impedance and polarization experiments agree within a factor of 2. The electronic diffusion coefficients in the tantalum containing melts have been determined from the current transients in the polarization experiments and typical values of ∽10-2 cm2 s-1 are found at 830 K with an activation energy of about 0.7 eV for 830⩽T/K⩽980. A simple two site model for electron hopping and intervalence charge transfer in these melts is discussed which qualitatively explains the observed parabolic potential dependence of the electronic conductivity and its temperature dependence.