Fig xA The cross section
As shown in Table 2, the temperature variation of capacitance of 0.2BA–0.8BT was within ±15% from −55 °C to 145 °C, which still failed to meet the requirement of X8R. Thus, Nb doping was chosen to improve the temperature stability. Ceramic samples with different Nb contents were prepared according to the method mentioned above. XRD patterns of 0.2BA–0.8BT–xNb (x = 0.01, 0.02, 0.03, 0.04 mol) ceramics all displayed 4-Methylhistamine desired perovskite phase with little secondary phases, as shown in Fig. 7. The EDS result proved the sheet grains (position 3) only contained Ba, Bi, Ti, O and Nb, which were consistent with the speculation from XRD patterns, BaBi4Ti4O15. While the secondary phase BaAl2O4 was formed in the matrix itself, which was confirmed by the EDS result of big oblate spheroidal grains (position 2). Fig. 8 showed the cross-section SEM micrographs of 0.2BA–0.8BT–xNb ceramics. A rather dense microstructure with low porosity was detected for all samples. As showed in Table 3, the incorporation of Nb into 0.2BA–0.8BT decreased the sintering temperature and simultaneously influenced the grain growth slightly, corresponding to a mycelium denser microstructure.