Thermopower studies of lithium–zinc mixed ferrites

Abstract

A series of Li–Zn mixed ferrites with composition formula Li0.5–0.5xZnxFe2.5–0.5xO4 is prepared by the solid‐state reaction method. The variation of lattice parameter with composition is explained on the basis of tetrahedral ionic radius. Thermopower studies are undertaken over a temperature range 300 to 750 K by the differential method. From the Seebeck coefficient S, the values of charge carrier concentration n and mobility μe are computed. The values of n are found to decrease while those of μe are increasing continuously with increasing temperature. On the basis of these results, a mechanism for the conduction in Li–Zn ferrites is suggested.

Thermoelectric Power of Cu-Zn Ferrites

“…It is noticed that the sign of the Seebeck coefficient for all samples is negative, indicting that the Cu-Zn ferrite behave as ntype semiconductor. The conduction mechanism in these ferrites is due to electrons [11], and many authors obtained similar results [12,13].…”

“…The conduction at lower temperature (below Curie temperature) is due to hopping of electrons [12] between Fe 3+ and Fe 2+ ions, whereas at higher temperature (above Curie temperature) due to polaron hopping [15]. [17] reported that the increase of Zn substitution tends to increase the Fe 2+ ions as demon-strated in above equation.…”

Conduction mechanism of zinc–magnesium W-type hexagonal ferrites

“…In the case of low mobility semiconductors like ferrites which have exceedingly narrow bands or localized levels, the charge carriers concentration per unit volume, n; can be written as [13] n ¼ N V…”

The conduction mechanism of Cu–Si ferrite

“…Due to the lattice vibrations, the ionic carriers are hopping from one site to another, thus leading to an exponential temperature dependence of the conduction. As a result, the mobility associated with carriers tends to increase exponentially with temperature according to the relation [21]:…”

“…8 shows that s decreases with increasing of temperature for the investigated compositions of Cu-Si ferrite. According to quantum-mechanical tunneling model [21,28], the exponent s factor is temperature independent. The large overlapping polaron model [31] predicted that s decreases with increasing temperature up to certain temperature after which it begins to increase with further increase of temperature.…”