The effect of sintering atmosphere on the microstructure and capacity-temperature characteristics (TCC) of Yb-Mg and Yb-Mn substituted BaTiO3 was investigated. The XRD and SEM results indicated the suppression of the solubilities of the acceptor ions when firing under reducing conditions. Mn was confirmed to promote the grain growth of Yb2Ti2O7 while Mg could suppress the grain growth of this second phase. The X8R specification (-55 to 150 degrees C, Delta C/C = +/- 15% or less) could be satisfied by firing under proper conditions for the two compositions. It is suggested that the change of the solubilities of the acceptor ions, as well as the valence states of the Mn ions would affect the TCC behavior of the core-shell-structured BaTiO3 materials. (c) 2006 Springer Science + Business Media, Inc.