LITHIUM-CATIONIC CONDUCTION IN THE LI4P3O7-ZN2P2O7 SYSTEM

Phase relations and conductance are studied in the Li4P2O (7)-Zn2P2O7 system. Two ternary compounds composed of 3Li(4)P(2)O(7) . 2Zn(2)P(2)O (7) (3:2) and Li4P2O7 . 6Zn(2)P(2)O(7) (1:6) and a wide range of solid solutions based on the high-temperature beta-modification of Li4P2O7 are found. The beta-solid solutions have high lithium-cationic conduct ivity (about 0.3 and 0.016 S cm(-1) at 700 and 400 degrees C, respecti vely) and on cooling to 385 +/- 5 degrees C undergo the eutectoid deco mposition accompanied by a jumpwise decrease in the conductivity. The Zn2+ additive stabilizes the beta-form of Li4P2O7 at temperatures belo w alpha reversible arrow beta transition (645 +/- 5 degrees C) and opt imizes the ratio between the number of mobile Li+ cations and vacancie s in the crystalline lattice available to them. The 3:2 and 1:6 compou nds have a lithium cationic conductivity of 6.3 x 10(-3) and 2 x 10(-6 ) S cm(-1) at 400 degrees C and 5.6 x 10(-2) and 2.5 x 10(-4) S cm(-1) at 600 degrees C, respectively.