Microstructure evolution and electric properties with addition amounts of dysprosium (DyO1.5) in (BaCa)(TiZr)O3 ceramics

In this study, the effects of various amounts of added DyO1.5 on the substitution mechanism for the (BaCa)(TiZr)O3 (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 Ca2+ 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 Ca2+ 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.