Internal and external relaxations in ZnNb2O6 ceramics

摘要

ZnNb2O6 ceramics were prepared via conventional solid-state reaction route. The dielectric properties of ZnNb2O6 were investigated in the temperature range from room temperature (RT) to 700 degrees C and frequency range of 10(3) - 2 x 10(6) Hz. Our results revealed that the sample exhibits an intrinsic dielectric response with a dielectric constant of similar to 20.9 below 150 degrees C followed by two thermally activated relaxations (R1 and R2) at higher temperatures. Both R1 and R2 are related to oxygen vacancies inherent in the sample. At temperatures higher than similar to 550 degrees C, an external relaxation (R3) induced by dc bias was observed. By means of the dielectric permittivity, electric modulus, impedance and admittance, R1 was attributed to be a dipole-type relaxation due to the hoping motions of oxygen vacancies. R2 and R3 were ascribed to be a Maxwell-Wagner-type relaxation resulting from the space charge due to the hoping vacancies blocked by grain boundaries and electrodes, respectively. (C) 2016 Elsevier Ltd. All rights reserved.