Electrical conductivity and thermoelectric power studies of aluminium-substituted lithium ferrites

Electrical conducrivity (sigma) and thermoelectric power (S) of polycrystal line aluminium-substituted lithium ferrites of various compositions have be en investigated as a function of composition and temperature. The Seebeck c oefficient is negative for all the ferrites under investigation showing tha t these ferrites behave as n-type semiconductors. The values of charge carr ier concentration have been computed from Seebeck coefficients. All the fer rites are found to exhibit clearly and well-defined transitions near the Cu rie temperature in Seebeck coefficient conductivity and carrier concentrati on vs. temperature plots. Activation energies of all the samples are calcul ated. An attempt is made to explain the conduction mechanism in these ferri tes. (C) 2000 Elsevier Science B.V. All rights reserved.