Abnormal Curie-temperature shift in Ho-doped BaTiO3 ceramics with the self-compensation mode

Nominal (Ba1-xHox)(Ti(1-x)Hx)O-3 ceramics (BHTH) were prepared at 1400 degrees C using a mixed-oxides method. The structure, microstructure, dielectric properties, and point defects of BHTH were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) spectroscopy, electron paramagnetic resonance (EPR), and dielectric measurements. Ho3+ in BaTiO3 prefers a self-compensation mode with a slight Ba-site preference, and the solubility limit of Ho3+ in the fine-grained BHTH (0.5 mu m) was determined by XRD to be x = 0.03. An abnormal phenomenon was observed: the Curie temperature of BHTH shifted towards high temperatures from 128 degrees C at x = 0.01 to 131 degrees C at x = 0.03. Ho3+ is inferred to be a potential codopant to achieve X8R specification when BaTiO3 is doped with Ho3+ and other types of ions.