Conduction mechanism in Y 3−2 xCa 2 xFe 5− xV xO 12 garnet ferrites

Abstract

A series of polycrystalline garnet ferrites with composition Y 3−2 x Ca 2 x Fe 5− x V x O 12 ( x=0.0, 0.2, 0.4, 0.6, 0.8 and 1.0), were prepared by the standard ceramic technique to study the effect of Ca 2+ and V 5+ ions substitution on their DC electrical conductivity, thermoelectric power, charge carrier concentration and charge carrier mobility at different temperatures. It was found that the DC electrical conductivity increases linearly with increasing temperature ensuring the semiconducting nature of samples. The lines representing the temperature dependence of σ dc are broken at two-phase transition temperature ( T σ1 , T σ2 = T C) giving three distinct regions (I, II and III). The activation energy for electrical conduction increases going from ferrimagnetic state (regions I and II) to paramagnetic state (region III) through the transition temperature T σ2 (Curie temperature). It also increases going from region I to region II thorough the temperature T σ1 . The dc electrical conductivity does not vary uniformly with Ca 2+ and V 5+ ion substitution. The values of the thermoelectric power were positive for samples of 0.0⩽ x⩽0.6 indicating that the majority of the carrier are holes in these samples while it were negative for samples of x⩾0.8 indicating that the majority of charge carriers are electrons in this samples. Using the values of the DC electrical conductivity and thermoelectric power, the values of the charge carrier concentration and the charge carrier mobility were calculated.