Indexed on: 01 Aug '99Published on: 01 Aug '99Published in: Journal of Electronic Materials
Through a sol-gel or sol-precipitation process Nb2O5-doped SrTiO3 was obtained from titanyl acylate precursors in acidic or alkaline solution, respectively. Nonstoichiometric powders were obtained by varying the Sr/Ti ratio in the starting materials. X-ray photoelectron spectroscopy (XPS) was used to investigate the surface properties of the powders and the sintered bulk ceramics. Excess Ti in the sol-gel process was converted to TiO2 (rutile) after calcination. In contrast, in the sol-precipitation process, the excess Ti was converted to Magnéli phases, which benefited the powders sinterability, and also enhanced the formation of Ti3+ on the powder surface, resulting in an abnormally high dielectric constant. The excess Sr in the sol-gel process was converted to SrCO3 and then to gaseous CO2 during sintering, which resulted in some cavities in the microstructure. In the sol-precipitation process, a structure of Srn+1TinO3n+1 was established and some near rectangular shaped, high-density grains were obtained.