In this study, the effects of various amounts of added DyO1.5 on the substitution mechanism for the (BaCa)(TiZr)O-3(BCTZ) ceramic sintered in a reduction atmosphere were investigated using X-ray diffractometer (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS).The Dy3+ ion occupation sites depended on the A/B ratio, whereas sites for the C2+ ions were affected by the DyO1.5 added amount and A/B ratio. For the specimens with A/B ratios below 1, Dy3+ ions mainly occupied the A-sites, which expelled some C2+ ions to occupy B-sites, based on XPS spectra and lattice parameter results. The Dy3+ ions occupied A-sites acting as donor, which resulted in a decrease in resistivity. For the samples containing 0.01 mol% DyO1.5, the Dy2Ti2O7 phase was observed and the resistivity increased rapidly due to the incorporation of Dy3+ ions into B-sites at A/B ratios below 1. As the added DyO1.5 increased to 0.015 mol%, a certain number of Ca2+ ions were forced to shift from B-sites to A-sites, as suggested by XPS spectra and lattice parameter results, which resulted in a decrease in resistivity. (c) 2005 Elsevier B.V. All rights reserved.