Development and application of a new method of determining the Gibbs energy of multicomponent systems of alkali metals

Detailed analysis is made and results are given of the application of a new version of effusion method of determining the Gibbs energy (thermodynamic activity) of $\text{Cs}$–$\text{Na}$, $\text{K}$–$\text{Na}$, $\text{Cs}$–$\text{K}$, and $\text{Cs}$–$\text{K}$–$\text{Na}$ binary and ternary systems of alkali metals. The activity is determined in terms of partial pressures of the components, measured by the effusion method by the intensity of their atomic beams. Because oxygen reacts with molten alkali metal, the effusion hole cannot be prepared in advance. Therefore, the effusion hole is made directly in the vacuum chamber by electron-beam pulse (linear electron accelerator is located within the chamber) after the effusion cell assumes the working temperature mode. The pressure interval in the experiment is intermediate between the Knudsen and hydrodynamic flow modes. The suggested generalized version of effusion method includes the range of pressures beyond the range of validity of the Hertz-Knudsen equation. The use of this method results in providing the boundary condition for the differential equation of chemical thermodynamics whose solution enables one to construct the Gibbs energy of the above-identified alloys in the temperature range $400 \le T \le 1200$ K and in the concentration range $0 \le x_i \le 1$.