Effects of B2O3 Content on the Microstructure, Electrical Properties, and Stability of ZnO-BaO-Based Varistors

B2O3 doped ZnO-BaO (ZBO) varistors, denoted as ZBO-xB(2)O(3) (where x = 0 wt.%, 0.02 wt.%, 0.04 wt.% and 0.08 wt.% of B2O3) are successfully prepared via a sol-gel method. The effects of B2O3 additive on the microstructure, electrical properties, and stability of ZBO varistor are studied using x-ray diffraction, ultraviolet-visible spectroscopy (UV-Vis), and field emission scanning electron microscopy. A single hexagonal ZnO phase is detected in ZBO-xB(2)O(3) with B2O3 added(.) Secondary phase Zn5B4O11 that is formed after adding B2O3 can replace other secondary phases in the samples. The average grain size increases from 11.71 mu m to 37.56 mu m as the B2O3 content increases from 0 wt.% to 8 wt.%. The band gap of the as-prepared ZBO-xB(2)O(3) increases gradually from 3.01 eV to 3.14 eV with increasing B2O3 contents. It is shown that ZBO-0.02B(2)O(3) possesses the highest nonlinear coefficient of 49.2, while ZBO-0.04B(2)O(3) exhibits the lowest leakage current density of 3.922A/cm(2). Furthermore, ZBO-0.04B(2)O(3) is able to demonstrate the best frequency stability, while ZBO-0.02B(2)O(3) displays the best temperature stability. Thus, based on the collective results, adding an appropriate amount of B2O3 to ZBO varistor can enhance its performance in all aspects.