The BCST ceramics possess pure tetragonal phase, when x = 0.04. Therefore, it can be suggested that orthorhombic phase and tetragonal phase coexist in the composition range of 0.02 < x < 0.04 for the BCST ceramics at room temperature. The changing of the lattice parameter with increasing of Sn content in BCST ceramics confirms the discussion above. Lattice parameters calculated from the diffraction data are presented in Table 1. Fig. 2 shows SEM micrographs of the BCST ceramics at x = 0.01, 0.02, 0.03 and 0.04, respectively. The microstructure of BCST ceramics at x = 0.01 is inhomogeneous
and some pores exist in the grain boundary