High insulation resistivity and low dielectric loss in (Ta, Al)-codoped BaTiO3 colossal permittivity materials

Low insulation resistivity is a key factor limiting the practical application of colossal permittivity (CP) ceramics in electronic components. In this study, BaTiO3-0.01Ta(2)O(5)-xAl(2)O(3) (BTAx, x = 0.005, 0.01, 0.015, 0.02) CP ceramics with high insulation resistance were successfully prepared by sintering in N-2. In particular, BTA0.015 ceramic exhibits CP (epsilon(r) = 2.01 x 10(5), 1 kHz), low dielectric loss (tan delta = 0.044, 1 kHz), high insulation resistivity (rho(v) = 1.4 x 10(9) Omega cm, DC voltage (DC) 100 V), and superior frequency and thermal stability (20 Hz-1 MHz, room temperature-350 degrees C). The polarization mechanism, dielectric and insulating properties were investigated by different atmosphere processing, scanning electron microscopy (SEM) X-ray photoelectron spectroscopy (XPS), and impedance analysis. Moderate doping of Al2O3 facilitates the construction of electron-pinned defect dipoles, which improves the dielectric properties. In addition, the ceramics feature an extremely fine grain size, which is conducive to suppressing the long-range migration of delocalized electrons. The combination of electron pinning defect dipole effects and internal barrier layer capacitance effects are the responsible for the giant dielectric constant. This research shows that the defect dipole-dependent polarization can be employed to design highly insulating BaTiO3-based CP ceramics.