Nano iron oxide-deposited calcium copper titanate/polyimide hybrid films induced by an external magnetic field: toward a high dielectric constant and suppressed loss
In this paper, we report promising dielectric characteristics of iron oxide-deposited nanosized calcium copper titanate (nano CCTO–Fe3O4)/polyimide (PI) hybrid films induced by an external magnetic field. Nano CCTO particles with a pure perovskite cubic structure and without impurity phases were prepared, and then Fe3O4 nanoparticles were deposited as discrete units on the surface of CCTO to fabricate nano CCTO–Fe3O4 hybrid particles. The effects of magnetic field treatments on the dielectric properties of the composites were investigated in detail. The nano CCTO–Fe3O4/PI hybrid films annealed under an applied magnetic field exhibited a substantial increase in dielectric permittivity, a slight increase in dielectric loss, and a decrease in the percolation threshold. For the hybrid composites subjected to a magnetic field treatment for 30 min at 90 °C, a high dielectric permittivity of 308 and relatively low dielectric loss of 0.60 at 100 Hz were simultaneously achieved when the content of nano CCTO–Fe3O4 was only 12 vol%. Such composites are promising for applications in electronic devices. The experimental results are well explained by percolation theory, which indicated that the enhanced dielectric properties of the hybrid films mainly originated from the large interfacial area and interfacial polarization induced by the external magnetic field.