Abstract: Er-Mg and Er-Mn doped BaTiO₃ systems were prepared by solid state reaction and the effects of sintering atmosphere on their microstructures and electrical properties were researched. XRD indicates that both samples sintered in different atmospheres have pseudocubic structure. For both specimens, the solubility limit of Er in BaTiO₃ is about 3.0mol%--4.0mol%, however the reducing atmosphere can suppress the solid solubility of acceptors such as Er, which lead to the formation of pyrochlore-type Er₂Ti₂O₇. SEM shows that Mn ions promote grain growth of Er₂Ti₂O₇ secondary phase, but contrarily Mg ions inhibit it. The results suggest that due to the effect of various sintering atmosphere, the solid solubility change of acceptors can affect the core/shell volume ratio in the grains, as well as the valence variety of Mn ions can shift the Curie temperature. Thus the capacitance-temperature characteristics are dramatically improved and two kinds of dielectrics sintered under the proper conditions can meet X8R specification.

Key words: BaTiO₃, secondary phase, solid solubility, multilayer ceramic capacitor