Flash Assisted Synthesis and Electrical Performance of MnO2-doped ZnO-Bi2O3-based Ceramics

How to prepare high-performance ZnO-based varistor ceramics in a short time and at a low temperature remains a key challenge. Flash sintering method provides an effective approach to solve this challenge. Here, MnO2-doped ZnO-Bi2O3-based dense varistor composite ceramics were successfully prepared by the flash sintering method at the furnace temperature < 750 ℃ in 60 s under the DC electric field of 300 V⋅cm− 1. The effects of MnO2 on the onset of furnace temperature, specimen temperature, and specimen conductivity were systematically investigated in the flash sintering process. The results of flash sintering show that the onset of furnace temperature of ZnO-Bi2O3-based composite ceramic containing 0.5 mol% MnO2 is only 704 ℃, which is significantly lower than that of undoped ZnO-Bi2O3-based varistor ceramic. The measurement results of the electrical properties for all flash-sintered composite varistors ceramics show that the composite sample containing 0.5 mol% MnO2 has the best electrical performance parameters compared with the undoped ZnO-Bi2O3-based varistor ceramic. The flash-sintered ceramic containing 0.5 mol% MnO2 obtained the nonlinear coefficient of 18, the leakage current of 16.82 µA, and the dielectric constant of 1221 at 1 kHz.

Znx-1CuxMn2O4 Spinels; Synthesis, Structural Characterization and Electrical Evaluation

This work presents the structural characterization and electrical evaluation of Znx-1CuxMn2O4 spinels, which are materials presented as secondary phases into the varistor ceramic systems. Samples were analyzed by X-ray diffraction, solid-state nuclear magnetic resonance, infrared spectroscopy, scanning electron microscopy and impedance spectroscopy. Although, the addition of copper to the ZnMn2O4 spinel did not produce morphological changes, the structure and electrical behaviors changed considerably. Structurally, copper addition induced the formation of partial inverse spinels, and its addition increases significantly the electrical conductivity. Therefore, the formation of Znx-1CuxMn2O4 spinels, as secondary phases into the varistor materials, may compromise significantly the varistor efficiency. Ceramic, Impedance Spectroscopy, spinel, Varistor, XRD.

Performance of (Y2O3,V2O5) Co-Doping TiO2 Ceramics

The present study investigated the effect of the sintering temperature and (Y2O3, V2O5) co-doping on the performance of TiO2 varistor ceramic which has lower varistor voltage and high nonlinear coefficient. The results showed that the TiO2-based varistor ceramic which doped with 0.35% mol and 0.25% mol of Y2O3 and V2O5 has good comprehensive electrical performance and excellent dielectric constant sintered at 1200°C. Its varistor voltage V1mA is 38.1V, nonlinear coefficient is 4.6.