Phase Structure and Electrical Conduction of CaTi_1?xSc_xO_3?δ Ceramics

The electrical conduction of CaTi_1?xSc_xO_3?δ ceramics is investigated by ac impedance spectra. A complete solid solution is formed, in which Sc (x≤0.17) substitutes for a Ti-site with the creation of oxygen vacancies. The samples of x≤0.1 contain two main resistances, the bulk resistance R₁ and the grain boundary resistance R₂. However, only R₁ and a low-frequency 'spike' representing charge build-up at the blocking metal electrodes are obtained for x≥0.15. CaTiO₃ ceramics doped with Sc exhibits a relativly high electrical conductivity. With increasing x, both σ₁ and σ₂ of CaTi_1?xSc_xO_3?δ increase first, reach a maximum value at x=0.05, and then decrease to x≥0.1.