ELECTRICAL TRANSPORTS OF LAFE1-XTIXO3 (X-LESS-THAN-OR-EQUAL-TO-0.10)

Electrical transports of LaFe1-xTixO3 (x less-than-or-equal-to 0.10) containing ligand holes (3d5L) were investigated by dielectric properties, ac and dc conductivities. A dielectric relaxation peak appeared with the activation energy which increased from 0.49 eV to 0.56 eV with increasing the amount of Ti ions. A thermal activation in the intensity of the peak was observed with the activation energy of 0.02 eV for LaFeO3 and 0.05 eV for Ti-doped specimens. These energies corresponded well to those obtained in dc conductivities. Compensation of holes by electrons introduced by substitutions of Ti4+ for Fe3+ was confirmed. The ac conductivity was found to obey an equation of sigma(omega) = A omega(s), omega being the angular frequency. There were three temperature ranges in the plots of beta (= 1-s) vs T; the low temperature range where beta congruent-to 0, the intermediate range where Pike's theory holds and the high temperature range where holes can hop over large energy barriers. These behaviours have been discussed in terms of small polarons of ligand holes.