The effect of processing conditions and porosity on the electrical properties of Y2O3-doped SrTiO3 internal boundary layer capacitors

Internal boundary layer capacitors of 0.8 mole% Y2O3-doped SrTiO3 were prepared by a co-milling process and then sintered in an oxidizing atmosphere between 1450-1550 degrees C for hold periods of 1-15 h. Large enhancements in the dielectric constant as a function of sintering conditions were observed, as compared to pure SrTiO3. The electrical properties of effective dielectric constant and effective conductivity were strongly correlated with each other depending on the frequency, and both properties decreased strongly with increasing porosity. To account for this strong dependence, three microstructural models were developed based on random porosity, porosity intersecting the grain boundary region, and porosity localized in the grain boundary region. For cases when the porosity preferentially reduces the grain boundary area, the models qualitatively predict a very strong dependence for the both the dielectric constant and conductivity on the pore volume fraction.