ICT2014 Abstracts

Doped perovskite titanate, ATiO₃ (A=Ba, Sr), is known to exhibit non-linear electric conductivity when it is in polycrystalline form. Such behavior is attributed to the formation of potential barrier at the grain boundary. Here, we focus on the influence of the potential barrier on Seebeck coefficient. To enhance the effect, bulk materials with grain size of 20-30 nm were prepared. Rare earth doping on the A site was employed to ensure n-type conductivity, such that Seebeck coefficient showed negative value as commonly observed. Interestingly, the absolute value was much larger than the expected value from the composition, suggesting trap of free carrier. Current-voltage property showed non-linear behavior, which indicates existence of potential barrier. We will discuss the contribution of the potential barrier to Seebeck coefficient based on the free-carrier information obtained by IR-spectroscopic-ellipsometry.