DEPENDENCE OF ELECTRICAL-CONDUCTIVITY (SIGMA) AND ACTIVATION-ENERGY OF LITHIUM FERRITE ON SINTERING TEMPERATURE AND POROSITY

The electrical conductivity (sigma) of lithium ferrite sintered at 950, 1000, 1050 and 1100-degrees-C was investigated in the temperature range of 300 to 1000 K. Three distinct regions have been observed in log (sigma-T) vs 10(3)/T curves for four samples of lithium ferrite sintered at different temperatures. The conduction in the first region is due to impurities. In the second and third region is due to ordered and disordered state of the material. The transition from the first region to the second region is due to lowering of symmetry. The transition from second to third region is due to magnetic transition, i.e. ferrimagnetic to paramagnetic state. The transition temperatures are nearly equal to the Curie temperatures of the materials. The porosity and activation energy were calculated. It was found that the electrical conductivity is progressively increasing with increase of sintering temperature while the porosity and activation energy decrease continuously. The Seebeck coefficient (Q), carrier concentration (n) and mobility (mu) of charge carriers have been discussed as a function of sintering temperature and temperature.