The AC impedance and variable temperature dielectric spectroscopic analysis of MnO2 doped and un-doped ZnO–V2O5 ceramics

Abstract

The electrical and dielectric properties of MnO 2 doped and un-doped ZnO-V 2 O 5 ceramics were studied by ac impedance and variable temperature dielectric spectroscopy. The results show that V and Mn ions simultaneously segregated at the grain boundaries to form an intergranular phase, increasing the resistivity of the intervening layer and the Schottky barrier at the grain boundaries, and then improving the varistor performance. An obvious loss peak appeared in all the samples, which means an effective depletion layer has formed. As for the samples sintered at 1,000°C for 2 h, the activation energy of the characteristic relaxation process is about 0.339 eV for 99.5 mol% ZnO ? 0.5 mol% V 2 O 5 and 0.352 eV for 99.0 mol% ZnO ? 0.5 mol% V 2 O 5 ? 0.5 mol% MnO 2 , respectively, which means this relaxation process is associated with oxygen vacancy V O Á .

Structural and dielectric properties of giant dielectric Na1/2Sm1/2Cu3Ti4O12 ceramics prepared by reactive sintering methods

“…[6] Possible causes of the non-ideal Debye behavior are the heterogeneity of the barriers, porosity, or electrode roughness. [26,27] Moreover, the radii of the arcs decrease with the increase of measuring temperature, suggesting a semiconducting behavior. Using ZsimpWin 3.10 software, the measured data of the complex impedance can be well fitted using an equivalent circuit of two elements phase element (CPE) of the electrically active component of the sample, i.e., grains, internal-boundaries, and electrode effect.…”

Effect of powder size on the microstructure and dielectric properties of ZnO ceramics

“…5(b), the f p for samples A and B are 1.78 and 82.54 Hz, respectively. It is clear that the relaxation phenomenon is related to the space-charge polarization since the relaxation frequency f p is lower than 100 Hz [20]. The interpreted R gb for samples A and B are 3.7 Â 10 7 V and 7.4 Â 10 5 V. Consequently, the calculated C gb for samples A and B are $2.42 nF and $2.75 nF, respectively.…”

Effects of Dopants and Processing Parameters on the Properties of ZnO-V2O5-Based Varistors Prepared by Powder Metallurgy: A Review

“…An amount of V 2 O 5 ≥ 0.5 mol.% improves the densification of ZnO-V 2 O 5 -based varistors by LPS, as V 2 O 5 melts at 681 °C, and the eutectic temperature of the binary ZnO-V 2 O 5 system is around 600 °C [ 126 , 127 ]. However, ZnO-V 2 O 5 -based systems with V 2 O 5 content over 2 mol.% usually exhibit unsatisfactory varistor properties due to excessive secondary phases formed at the GBs between ZnO grains.…”