Large dielectric constants and good thermal stability of Nb2O5-doped BaTiO3–Bi(Mg1/2Ti1/2)O3 ceramics with core–shell structure

0.96BaTiO3-0.04Bi(Mg1/2Ti1/2)O3 (0.96BT-0.04BMT) + y wt.% Nb2O5 ceramics (0.0 ≤ y ≤ 2.0) were sintered at 1275 °C to fabricate a ceramic with a large εr for an X8R multilayer ceramic capacitor (MLCC). Addition of Nb2O5 afforded a core–shell structure, and the compositions of the core and shell regions were similar to those of BT and BT-BMT, respectively. The sample (y = 1.25) exhibited a large εr of 2285 with a good temperature stability satisfying the X8R specification because of a broad shell-region phase-transition peak at −17 °C and a decreased εr of the core-region phase-transition peak. The 0.1 wt% BaO–CaO–SiO2 (BCS) was used to reduce the sintering temperature, and the 9-layered MLCC produced using a BCS-doped 0.96BT-0.04BMT + 1.25 wt% Nb2O5 ceramic at 1200 °C showed a large capacitance of 67 nF with a good temperature stability thus complying with EIA-X8R regulations.