A-site stoichiometric and sub-stoichiometric (La,Sr)1-x(Ga,Cr)O3 perovskites with various Cr contents, and where x was 0 or 0.05, were prepared by using a ceramic route. Structural characterisation was carried out by means of X-ray diffraction, and the conductivity was determined by using impedance spectroscopy and direct-current measurements as a function of temperature and O partial pressure. It was found that the Cr content affected the activation energy for conductivity, and a transition from predominantly ionic conduction to electronic conduction was observed. Thus, p-type conductivity was thought to predominate in air when the Cr content was equal to, or greater than, 20%. The A-site sub-stoichiometry had no effect upon improving the electrical properties.

Ionic and Electronic Conduction in Stoichiometric and Sub-Stoichiometric Perovskites. D.Westphal, G.C.Mather, F.M.B.Marques, S.Jacobs, U.Guth: Solid State Ionics, 2000, 136-137, 19-24