X-ray photoelectron spectroscopy and electrical properties studies of nonstoichiometric Nb2O5-doped strontium titanate ceramics prepared by sol-precipitation process

Nonstoichiometric Nb2O5-doped SrTiO3 samples were obtained from a titanyl acylate precursor by sol-precipitation process. The samples, containing 5% excess titanyl acylate precursor sintered in N2-atmosphere, were ease to get the Magnéli phases, and the Ti3+ concentration of the sample reached a maximum at 1350 °C. At this temperature the sample had its lowest electrical resistivity (1.8×105 Ω-cm). In contrast, for the stoichiometric Nb2O5-doped SrTiO3 powders in which we simply added 5% TiO2 and sintered in N2 or air, only a few Magnéli phases were observed and the Ti3+ concentration was lower than in the samples made with 5% excess titanyl acylate. Incidentally, the electrical resistivity measured in these samples was higher.