Dielectric study on Zn1−x Mg x O ceramic materials prepared by the solid-state route

Abstract

The present work investigates the structural and dielectric properties of Zn1−x Mg x O composites prepared by the standard sintering method at 1200 °C during 24 h and doped with different weight percentages of MgO (x = 0–40 %). For this purpose, the scanning electron microscopy (SEM) was used to study the effect of the magnesium’s proportion on the morphology and crystallinity of the obtained samples. The SEM observations have shown rougher surfaces of the samples covered by grains having prismatic shapes and different sizes. The dielectric properties of the ceramics were investigated by spectroscopic impedance at different temperatures and frequencies, thus showing a frequency-dependent dispersion of the permittivity constants and dielectric losses. From these measurements, the relaxation processes were identified and their activation energies extracted. Dielectric responses were correlated with the microstructure and chemical composition of the ZnMgO composites. The mechanisms of ac conductivity are controlled by the polaron hopping and the electron tunneling models. Concerning the tunneling model, two types corresponding to the overlapping large polaron tunneling model for the composites Zn0.9Mg0.1O and Zn0.8Mg0.2O and the small polaron tunneling model for the composites Zn0.64Mg0.36O (in the frequency range 1.7 × 104 Hz–1 MHz) and Zn0.6Mg0.4O were observed. Besides, one type of hopping model corresponding to the correlated barrier hopping for the composites ZnO and Zn0.64Mg0.36O (in the frequency range 6 × 102–1.7 × 104 Hz) was noted.