ELECTRICAL-CONDUCTIVITY AND PHASE-DIAGRAM OF THE SYSTEM LI2SO4-LI3PO4

The result of electrical conductivity measurements, X-ray powder diffraction and DTA on the Li2SO4Li3PO4 mixtures are presented and the phase diagrams is determined. A large region of solid solution Li2+xS1-xPxO4 (0<x≤0.7) with α-Li2SO4 structure is found between 563°C and 1121°C. In this region, the electrical conductivity decreases slightly according to a "paddle-wheel" mechanism and not to a "percolation" mechanism. At lower temperatures, a considerable increase of the electrical conductivity occurs for the (Li2SO4)0.7-(Li3PO4)0.3 mixture which corresponds to a solid two-phase region; this is due to the classical "dispersal" mechanism which occurs in composite ionic conductor although there is not an eutectic mixture in this system. Also, no intermediate phase exists in this system. © 1990.