Microstructure effect on dielectric Properties of MgO-doped BaTiO₃-BiYO₃ ceramics

MgO-doped 0.97BaTiO₃-0.03BiYO₃ (0.97BT-0.03BY) polycrystalline ceramics were prepared by the solid-state sintering method. Then the structural, dielectric and resistant properties were investigated as functions of MgO addition. Microstructure was studied using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive spectrometry (EDS). The results show that Bi³⁺, Y³⁺ and Mg²⁺ ions exhibit nonuniform distribution behavior in BT-BY ceramics, demonstrating the existence of a core-shell structure, which plays important roles in the capacitance-temperature characteristics, where 0.97BT-0.03BY with the addition 2.2-2.8 at% MgO meets the Electronic Industries Association (EIA) X8R (-55 to 150 °C, ΔC/C_{25 °C}=±15% or less) specification. Moreover, the fine-grained samples with core-shell structure show much higher bulk resistance than the coarse-grained samples over the studied temperature range, which is attributed to the higher proportion of grain boundaries and the lower concentration of the effective acceptor.