Dielectric properties of a three-phase Fe-Ni-BaTiO3 composite

Fe-Ni-BaTiO3 three-phase composites with super high dielectric constant were successfully prepared by sintering BaTiO3 with various amount of metal (Ni and Fe with a fixed mol ratio of 78:22) in nitrogen atmosphere at 1250 degrees C for 2h. The impedance and the dielectric properties were measured by an Agilent 4294A precision impedance analyzer, and the dc conductivity was measured by a Keithley 6571 high resistance meter. The results indicate that this type of composite undergoes an insulator-conductor transition with increasing metal concentration and the dielectric constant diverged near the percolation threshold. The dielectric constant reaches as high as 22000 when f(Metal) = 0.23, which is about 12 times that of the BaTiO3 matrix, while the dielectric loss keeps still a low and stable value of about 0.08 with increasing metal concentration. And the dielectric relaxation shows a notable Maxwell-Wagner characterization, which suggests that conduction mechanisms may play an important role in the dielectric response.