Study of Defects by Rietveld Technique and Gas Response of Excess-Iron Zinc Ferrite

Abstract

It has been shown that by regulating excess iron content in spinel zinc ferrite it is possible to enhance its gas response. In this work relationships between structural properties and gas response of the non-stoichiometric zinc ferrites are studied. Stoichiometric and excess iron spinel zinc ferrite nanomaterials were synthesized by using sol-gel combustion. Rietveld refinement of site occupancies from powder XRD data shows that excess iron zinc ferrites contain vacancies on oxygen positions, Fe²⁺ on octahedral crystallographic B sites, and Fe³⁺ on the A site. As revealed by complex impedance spectra, with increasing oxygen vacancy concentration the depletion layer width decreases. At the same time, increasing oxygen vacancy concentration increases oxygen adsorption for reaction with a test gas, thus increasing the gas response of spinel zinc ferrite. Long term stability of the non-stoichiometric excess iron spinel zinc ferrite gas sensors will be discussed in this work.