Low dielectric loss induced by annealing in (La0.5Nb0.5)0.005Ti0.995O2 colossal permittivity ceramics.

Low dielectric loss (tanδ < 0.05) within a frequency range of 20 Hz–2 MHz and a temperature range of 25–350 K was obtained through an optimized annealing process in colossal permittivity (CP) (εʹ > 10⁴) (La_0.5Nb_0.5)_0.005Ti_0.995O₂ ceramics. The effects of annealing on two important dielectric relaxations, electron-pinned defect-dipole (EPDD), and Maxwell–Wagner polarization were explored. An enhancement of activation energy (E_a) value and a large distribution of relaxation time τ were detected in EPDD relaxation for the ceramics annealed at 1123 K. The EPDD polarization was destroyed, accompanied by the disappearance of CP in the high annealing temperature range (> 1273 K). Impedance spectroscopy analysis suggested that grain boundary impedance could greatly enhanced as the ceramics were annealed at 1123 K. Strong electrode-material-dependent dielectric properties were detected, and a high tanδ was observed after the insulating surface layer was removed. The CP and low tanδ were ascribed to the maintenance of EPDD polarization, the enhancement of grain boundaries resistance, and the formation of an insulating surface layer through appropriate annealing. [ABSTRACT FROM AUTHOR]