The structure, electrical properties and chemical stability of porous Nb-doped SrTiO3 - experimental and theoretical studies

A series of porous SrTi1-xNbxO3 samples (with x - 0, 1, 2 and 3 mol%) were prepared by wet synthesis and sintered at 1573 K. Single phase samples were obtained for each composition, as confirmed by XRD measurements. For all samples, aging tests in CO2/H2O atmosphere and electrochemical impedance spectroscopy measurements in air and hydrogen (reduced) atmosphere were carried out. Simultaneously, for model superstructures corresponding to 2 and 3 mol% experimental compositions, FP-LAPW DFT calculations of electronic structure and bonding properties (using QTAiM approach) were performed. Both experimental and theoretical results show an increase of cell parameters with increasing niobium amount. The influence of the amount of niobium on the microstructure of the synthesized samples as well as on their chemical stability was also observed. Electrical properties measurements showed different conduction mechanism for synthetic air and reduced atmosphere, i.e. mixed ionic-electron conduction and dominating electron conduction, respectively.