Borosilicate Frit Addition Impact on the Structure and Electric Behavior of ZnO Nanoparticle-Based Varistors

Abstract

In this study, ZnO-Bi2O3-Mn2O3 varistors fabricated from the nanoparticle size of ZnO powder and doped with borosilicate frit were prepared via the conventional ceramic processing method. The influence of different borosilicate frit concentrations (0-3.0 mol%) on the sintering, microstructure enhancement, and nonlinear behavior of the ZnO-Bi2O3-Mn2O3 system was investigated. Results show that the borosilicate frit was liquefied to improve the density of the ceramic during sintering and found to have significant effects on the ZnO varistors, especially on enhancing grain growth even at a low doping concentration of only 0.5% mol. The strong solid-state reaction in the varistor made from 20 nm ZnO powder during sintering may be attributed to the high surface area of the 20 nm ZnO nanoparticles. X-ray diffraction analysis indicated that the addition of borosilicate frit to the ZnO-Bi2O3-Mn2O3 varistor system results in the formation of Zn4O(BO2)6 during sintering if too much borosilicate frit was added (over 0.5% mol). Borosilicate frit doping also significantly influenced the electrical properties of the varistor with a marked drop in the breakdown voltage from 545 V to 188 V with increase of borosilicate frit doping concentration. The resistivity also experienced a dramatic drop from 535.7 kΩ.cm to 133.5 kΩ.cm with increase of borosilicate frit doping contents. Therefore, borosilicate frit doping can be used to control the structural properties and breakdown voltage of ZnO-Bi2O3-Mn2O3 varistor system fabricated from 20 nm ZnO powder.