The impact of Ba substitution in lanthanum‑strontium ferrite on the mobility of charge carriers

Abstract

The effect of barium content on the mobility of oxygen ions and that of electronic charge carriers in La0.49Sr0.5–xBaxFeO3–δ (x = 0, 0.25, 0.50) was studied by means of electrical conductivity modeling with the use of the results of the conductivity and oxygen content measurements depending on the partial pressure of oxygen in the gas phase. In accordance with the simulation results, an increase of oxygen content in oxides leads to increased mobility of p-type charge carriers, while it does not affect the mobility of n-type charge carriers. An increase in barium content has been shown to result in decreasing the mobility of all charge carriers. The mobility of electrons, holes, and oxygen ions has been found to be decreased at 950 °C by factors of 1.9, 2.4, and 2.7, respectively, as a result of half of the strontium substitution with barium. A negative effect of barium on the mobility of electronic charge carriers is believed to be conditioned by a FeO bond elongation. A decrease in the mobility of oxygen ions occurs mainly due to local distortions of the crystal lattice near large barium ions. The average mobility of holes in oxides has been found to be about twenty times higher than that of electrons. Such a strong difference is explained by a difference in the electronic configuration of iron ions responsible for the transfer of holes and electrons.