ABSTRACT
The microstructures and electrical behaviour of two doped polycrystalline strontium titanate ceramics have been compared. One sample was made semiconducting through the addition of niobium as a donor dopant, while the other exhibited internal boundary layer capacitor behaviour through the additions of niobium as a donor dopant and sodium as an acceptor dopant, with a novel processing procedure in which an uninterrupted single firing process was used. Clear differences are seen in the Fresnel fringe profiles of grain boundaries and the second phases found in the two materials which relate directly to the differences seen in I-V curves and are consistent with a simple boundary barrier model we have established.
