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Various lead-free ceramics have been investigated in search for new high-temperature dielectrics. In particular, Bi4Ti3O12 is a type of ferroelectric ceramics, which is supposed to replace lead-containing ceramics for its outstanding dielectric properties in the near future. Ferroelectric ceramics of Bi4Ti3O12 made by conventional mixed oxide route have been studied by impedance spectroscopy in a wide range of temperature. X-ray diffraction patterns show that Bi4Ti3O12 ceramics are a single-phase of ferroelectric Bi-layered perovskite structure whether it is calcined at 800℃ or after sintering production. This study focused on the effect of the grain size on the electric properties of BIT ceramics. The BIT ceramics with different grain sizes were prepared at different sintering temperatures. Grain becomes coarser with the sintering temperature increasing by 50℃, relative permittivity and dielectric loss also change a lot. When sintered at 1 100℃, r values peak can reach 205.40 at a frequency of 100 kHz, the minimum dielectric losses of four different frequencies make no difference, all close to 0.027. The values ofEa range from 0.52 to 0.68 eV. The dielectric properties of the sample sintered at 1 100℃ are relatively better than those of the other samples by analyzing the relationship of the grain, the internal stresses, the homogeneity and the dielectric properties. SEM can better explain the results of the dielectric spectrum at different sintering temperatures. The results show that Bi4Ti3O12 ceramics are a kind of dielectrics. Thus, Bi4Ti3O12 can be used in high-temperature capacitors and microwave ceramics.