MOLAR VOLUMES OF THE COMPONENTS OF LI3N, LI3ALN2, AND 0.6LI4SIO4-CENTER-DOT-0.4LI3PO4 LITHIUM-CONDUCTING SOLID ELECTROLYTES

The molar volumes of Li3N in the compounds of Li3N and Li3AlN2 and the molar volume of Li2O in 0.6 Li4SiO4 . 0.4 Li3PO4 were calculated from the maximal values of the baro-emf that were reached after attaining an equilibrium in the cells of the type (+)Ni\SE\SE\Ni(-), where SE i s a solid electrolyte and SE is the same electrolyte after treatment with hydrostatic pressure. The calculated thermodynamic molar volume i s considerably higher than the molecular volume that was calculated fr om the crystal structure. A model of solid lithium-conducting electrol ytes has been constructed.The model consists in the formation of ionic polarons in which lithium cations are not free charges. The polarons have as circle a radius greater than the crystal unit ceel. The action of external fields activates the polaron-accupied region of the cryst al. A zone, in which the field of the central ion drops to a value neg lible compased with the interaction among the polarons, should be cons idered as forming the polaron limits.The crystal as a whole is charact erized as an order medium having certain mean macroscopic characterist ics only beyong the polaron limit.