Résumé
The bonding energy can be written as a linear combination of three independent energy contributions namely, an electrostatic, a covalent and a polarization term which are expressed as a function of the alkali metal cation radius. The model is then used to fit the evolution of the activation energy for the dc conductivity with the various alkali metal cations in the following test cases: a clay mineral (montmorillonite), two zeolites (faujasites Fau-X and Fau-Y), three glassy oxides (a silicate with two alkali contents and a triborate). Two typical behaviours can be distinguished: i) the considered solid oxide is either porous or supposed to have enough free volume for the displacement of the cations and then the model can be applied, ii) the compactness of the structure is such that the analytical expression for the activation energy of dc conductivity contains an additional term and then the model cannot be directly used. However, if this additional energy is known, then it is possible to estimate the alkali metal bonding energy and to properly reproduce it from the model. Finally, it is shown that the model yields significant information about both the nature of the alkali metal bond and the microscopic mechanism involved in the dc conductivity.