Figure 2 shows the microstructure o

Figure 2 shows the microstructure of ceramics with different sintering methods and compositions. All the samples exhibit homogenous grains due to the uniform distribution of additives around nano-BaTiO3 particles through the chemical coating process. The grain sizes of samples prepared by different sintering processes seem similar, around 100–130 nm. Moreover, as listed in Table I, the density of the ceramics with the same composition is nearly the same. These results indicate that neither the grain size nor the bulk density is the dominant factor, which causes the different TCC characteristics.