The electrical conductance properties of SrFeO2.5+x thin-films and applications to gas sensing

The electrical conduction properties of SrFeO2.5+x thin-films when exposed to oxygen/nitrogen atmospheres have been investigated under isothermal and non-isothermal conditions. The ranges of oxygen partial pressure and temperature were 0.05<p(O-2) < 101kPa and 40< T< 480 degrees C, respectively. Over these ranges p-type semiconduction is exhibited. Isothermally, and at T > 350 degrees C where the kinetics of oxygen exchange in the bulk SrFeO2.5+x is rapid, there is a logarithmic relationship of conductance with p(O-2). At lower temperatures, a combination of mechanisms contribute to conductivity. These include intrinsic temperature dependencies of electronic conduction, surface oxygen reactivity and film annealing effects. A series of programmed temperature changes has been used to help determine the dominant conduction mechanism at different temperatures.