Transition from hopping conduction to band conduction in LaFe x Ni1–x O3

Abstract

Abstract Electrical transport and the nature of carriers in the homovalent substitution LLaFe x Ni1–x O3 were investigated as a function of component, in the temperature range 10K–300K, by dielectric properties, dc and ac conductivities and thermopowers. At x > 0·6, the positive thermopowers indicate the major carriers of holes which are introduced by the superexchange rule. At x = 0·9 and 0·8, a hopping process of small polarons of holes contributes predominantly to the electrical transport at temperatures higher than about 170K, which is confirmed by both the dielectric measurements and the Arrhenius relations between [sgrave]T and 1/T. As the temperature falls below 170K, the non-Arrhenius conductivities appear, which is consistent with the fact that the small-polaron hopping becomes usually non-Arrhenius as the temperature is reduced. At x – 0·7 and 0·6, the frequency dependences of the dielectric loss tangent indicate reorientation of polarons deeply bound to traps at temperatures below about 70 K. A...