Porous Y and Cr–doped SrTiO3 materials—electrical and redox properties

Highly porous materials in the Sr0.96Y0.04Ti1-xCrxO3 system (where x = 0, 2, 4, 8 mol.%) were obtained by wet synthesis method. The structural and electrical properties of these materials were determined together with the ability to participate in oxidation/reduction reactions, since yttrium is responsible for high electrical conductivity in reducing atmosphere and chromium is a factor affecting the catalytic properties. For the material with the highest assumed amount of chromium, the small content of an additional phase (Cr2O3) was observed. SrTiO3 lattice parameters together with the results of temperature-programmed reduction (TPR) and temperature-programmed oxidation (TPOx) tests and Seebeck coefficient measurements allowed to determine the oxidation states of chromium in the received materials. It was shown that introduction of Y into strontium sublattice stabilises the strontium titanate structure and affects the oxidation state of chromium incorporated into the titanium sublattice. The defect structure in Sr0.96Y0.04Ti1-xCrxO3 system is a complex problem, since yttrium is a donor type dopant and chromium due to the possible +3 and +6 oxidation states can be considered both acceptor and donor type one. Thus, a change in the conduction mechanism with the chromium content was observed in both oxidising and reducing atmosphere.