Colossal permittivity and impedance analysis of niobium and aluminum co-doped TiO2 ceramics
Niobium and aluminum co-doped TiO2 ceramics, i.e., (Nb0.5Al0.5)xTi1−xO2 (x = 0, 0.01, 0.05, 0.1, 0.15, abbreviated as NAT100x) were synthesized via a solid-state reaction route. As could be seen from X-ray diffraction (XRD) patterns, all samples were in pure rutile phases. A colossal permittivity (CP) over 105 with relatively low dielectric loss could be noted in the NAT10 ceramic. Additionally, the high dielectric permittivity (>105) could be maintained over a wide temperature range of −100–250 °C and frequency range of 102 to 106 Hz, respectively. This indicated that the dielectric property of NAT10 possessed superior temperature-dependent and frequency-dependent stability. Analysis of impedance spectroscopy and current density vs. electric field plots revealed that the CP was attributed to an internal barrier layer capacitance effect.