Structure and transport properties of donor-doped barium strontium cobaltites

In this work, Nb-substituted barium strontium cobaltites Ba0.5Sr0.5Co1-xNbxO3-δ (x = 0 – 0.4) have been fabricated and studied. The structural analysis showed that the Nb content influences the lattice constant as well as the distance between the (Co, Nb) and oxygen atoms. The study of morphology of samples showed that the Nb content does not change the porosity, grain size and morphology of the ceramics. The total electrical conductivity was studied as a function of temperature and pO2/pH2O. It was shown, that total conductivity is influenced by the cobalt to niobium ratio while the conduction mechanism was similar in all analyzed samples. Transport properties and the presence of protonic conductivity were studied in a dry and humidified atmosphere. A non-negligible difference between total conductivities in dry and wet atmospheres below 500 °C was observed what indicates the presence of protonic defects in these structures. Hydrogenation as a predominant protons formation mechanism was proposed.