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Kinetic properties of Ni(II) in eutectic LiF-NaF-KF (FLiNaK) molten salt were determined at T = 748–823 K using cyclic voltammetry (CV), square wave voltammetry (SWV), and chronoamperometry (CA) measurements using a glassy C working electrode, Ni(II)/Ni reference electrode, and Ni counter electrode. Reduction of Ni(II) to Ni(s) was determined to be a single step, two-electron transfer process. Diffusivity values were calculated using the Berzins and Delahay equation and semi-integral electroanalysis from the CV measurements as well as using the Cottrell equation from the CA measurements. Diffusivity of Ni(II) in molten FLiNaK at T = 748–823 K was determined to be 3.27 × 10–7 –3.04 × 10–6 cm² s –1 with an activation energy of 62–104 kJ mol–1 . The estimated kinetic properties varied appreciably among methodologies possibly due to inherent assumptions in theory regarding reversibility and unit activity during Ni metal deposition on the working electrode. [ABSTRACT FROM AUTHOR]

The thermochemical properties of Sr-Sn alloys were determined by electromotive force (emf) measurements to evaluate liquid tin as an interacting electrode material for separating alkaline-earth elements from molten salt solutions. A Sr(s)|CaF2-SrF2|Sr(in Sn) cell was used to measure emf values for twelve Sr-Sn alloys at mole fractions xSr = 0.02-0.43, allowing the determination of thermochemical properties such as activity and partial molar quantities of Gibbs energy, entropy, and enthalpy of Sr at 730-1110 K. Activity values of Sr in liquid Sn were as low as 6.9 × 10-12 at 800 K and xSr = 0.02 indicating highly non-ideal solution behavior between Sr and Sn. Phase transitions were also determined from the emf data and were validated via differential scanning calorimetry (DSC). Through the combination of emf measurements for thermochemical properties, X-ray diffraction (XRD) for phase constituents, and DSC measurements for phase transitions, this work established more complete thermodynamic properties of the Sr-Sn binary system. [ABSTRACT FROM AUTHOR]

In this study, amorphous lithium lanthanum titanate (LLTO) powders were prepared by a sol-gel method with an all alkoxide based route. Results showed that unlike its crystalline counterpart which turns into an electronic conductor in direct contact with lithium metal, amorphous LLTO remains to be an ionic conductor and hence is compatible with lithium metal as solid electrolyte although it also undergoes lithium insertion and the consequent reduction of Ti4+ to Ti3+. This striking difference between crystalline and amorphous LLTO could be ascribed to the atomic configuration difference, ordered versus disordered. The electronic states of a disordered system could be localized. It was found that the transference number of lithium ions of amorphous LLTO is over 82%. Our results on electrochemical measurements indicated that amorphous LLTO is stable with blocking electrodes up to 12 V, which can potentially be used with high voltage cathode materials. [ABSTRACT FROM AUTHOR]

Amorphous lithium lanthanum titanate (LLTO) thin films were successfully prepared by a sol-gel method with an all-alkoxide based route. The thin film resistance was determined from the complex spectra by fitting experimental data to the equivalent circuit. The ionic conductivities of amorphous LLTO thin films were 4.5 x 10-6, 6.9 x 10-6, 1.3 x 10-5, and 3.8 x 10-5 S/cm at 30°C, 50°C, 70°C, and 90°C, respectively. The activation energy of lithium ion conduction in the thin film was evaluated to be 0.36 eV in the temperature range of 30-90°C. The structure of amorphous LLTO was predicted by the ab-initio molecular dynamics (AIMD) simulations and analyzed by partial pair distribution functions, coordination numbers and Voronoi tessellation. It is observed that the local environment of Ti in amorphous LLTO is quite similar to that in the crystal state but the atomic packing is much less dense. The ionic diffusivities were derived from the mean square displacement curves and the conductivities were evaluated from the Nernst-Einstein's relation, showing good agreement with experimental data. The good ionic conductivity of amorphous LLTO is attributed to its open and disordered structure with large excessive volumes. [ABSTRACT FROM AUTHOR]

Thermodynamics of defects in the (LaxCa1-x)FeO3-δ perovskite is modeled by means of the CALPHAD approach. In this phase, the A-sites are occupied by La+3 and Ca+2, and Fe in the B-site is known to exist in +2, +3, and +4 oxidation states depending on the oxygen vacancy concentration. Therefore, the ionic sublattice model: (La+3, Ca+2)(Fe+2, Fe+3, Fe+4)(O-2, Va)3 is used to describe the phase, and the model parameters are evaluated from experimental oxygen nonstoichiometry and phase equilibria data. With the Fe+2 and Fe+4 treated as the major species in the B-site, the calculated phase diagrams are in good agreement with the experimentally reported phase equilibria data. The concentration of various defects in (LaxCa1-x)FeO3-δ as a function of oxygen partial pressure and temperature are calculated at different concentrations of Ca. At high oxygen partial pressures, Fe+4 is predicted to be dominant while Fe+2 is dominant at low oxygen partial pressures. [ABSTRACT FROM AUTHOR]