Ionic and electronic conduction in stoichiometric and sub-stoichiometric perovskites

A-site stoichiometric and sub-stoichiometric (La,Sr)1−y(Ga,Cr)O3−δ perovskites, with y=0 or 0.05 and variable Cr content, were prepared by the ceramic route. Structural characterisation was carried out by X-ray diffraction (XRD). Electrical conductivity of samples was determined by impedance spectroscopy and dc measurements, as a function of temperature and oxygen partial pressure, in order to study the role of composition on the electrical properties. Cr content affects the activation energy of the electrical conductivity, and a transition from dominant ionic conduction to electronic conduction is observed. p-type conductivity is believed to dominate in air for materials with Cr content equal or higher than 20%. A-site sub-stoichiometry had no effect on improving the electrical properties.