Thermodynamic and Mass Transport Properties of  “ LiAl ”

The compositional variations of the thermodynamic and mass transport propert ies of the ~ phase "L iAr ' in the l i th ium-aluminum system have been investigated over the temperature range from 415 ~ to 600 ~ At 415 ~ the emf of the single phase "LiAI " lies between 300 and 70 mV relat ive to pure Li and this corresponds to a 'Li act iv i ty increasing from 0.0063 to 0.31 over the phase stabi l i ty range from 46.8 to 55.0 atomic percent Li. At the ideal stoi-chiometry, the standard Gibbs free energy of formation of "LiAI " is--29.2 k J /mo le at 415 ~ and the corresponding enthalpy and entropy are--43.3 k J /mo le and--20.6 J /mole ~ respectively. Two different electrochemical t ransient echniques have been used to measure the chemical diffusion co-efficient in "LiAI " as a function of the stoichiometry; the exper imental results obtained are in good agreement. On the l i thium deficit side of the ideal stoi-chiometry, the chemical diffusion coefficient increases with decreasing Li con-centration, becoming about 10-4 cm2/sec near the phase boundary. On the