It is demonstrated that either a strong nonlinear or a nearly Ohmic behavior in current-voltage relationship can be distinctively represented in Sc-doped polycrystalline CaCu3Ti4O12, with variation in the initial composition of samples. Through conductive atomic force microscopy and impedance spectroscopy, such a definitive difference in the electrical property was found to depend on the presence of a large electrostatic barrier at the grain boundaries. The effect of Sc ions on the boundary potential barrier and the conductance of single grains is discussed. Findings suggest a different site selectivity of Sc in the lattice in terms of the initial cation stoichiometry.

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