Study on Occupation Behavior of Y2O3 in X8R Nonreducible BaTiO3-Based Dielectric Ceramics

Abstract

The effects of Y2O3 on BaTiO3–MgO–MnO2–CaZrO3 nonreducible ceramics were investigated. Specimens with Y2O3 contents ranging from 1.0 to 2.5 mol % were prepared via the solid state method. The Curie temperature (Tc) and the electrical properties were closely related to the occupation behavior of yttrium, which is known as an amphoteric element. Tc increased almost linearly as a function of Y2O3 content when the doping content was low. Transmission electron microscopy (TEM) indicated a typical “core–shell” structure. The lattice parameters corresponding to the grain cores and the shells were determined by X-ray diffractometry (XRD) separately. The relief of the internal stresses arising from the lattice mismatch was responsible for the Tc shift. The specimens doped by a high level of Y2O3 can fulfill the EIA X8R specification with a high dielectric constant (εRT > 2400) and a low dielectric loss (tan δ< 1.1%). A high insulation resistivity and a slow degradation rate were obtained when a sufficient amount of Y2O3 was incorporated, which were attributed to the substitution of Ti4+ and the formation of a donor–acceptor complex.