PHASE-TRANSITION AND TRANSPORT-PROPERTIES OF SOLID LI2CO3

The electrical transport properties such as ac electrical conductivity (sigma), dielectric constant (epsilon') and thermoelectric power (theta) of pure polycrystalline lithium carbonate in the form of pressed pellets are studied in the temperature range 300-940 K. The solid-solid high temperature phase transition is detected at 683 K and the activation energies found in low and high temperature phases are 0.95 eV and 0.74 eV, respectively. The dielectric constant values at room temperature 300 K are obtained as 21 at 100 Hz, 17 at 1 kHz and 13 at 10 kHz. The thermoelectric power is found to be independent of time and pressure of pelletisation, and the heats of transport 4.46 eV and 2.05 eV found in low and high temperature phases suggested that the pure lithium carbonate is an average ionic conductor as these are much higher than those obtained by electrical conductivity method.