High-performance and low-voltage SnO2-based varistors

Abstract

This paper presents the results of a thorough study conducted on the action mechanism of one-dimensional single-crystalline SnO 2 nanobelts in decreasing the breakdown electric field (E b) in SnO 2-based varistors. The proposed method has general validity in that our investigation was focused on the traditional varistor composition SnO 2-CoO-Cr 2 O 3-Nb 2 O 5. To accomplish our study objective, two methods of decreasing E b value were compared; one involving the increase in average grain size of the varistor through the sintering time and the other one related to the addition of nanobelts. The morphological results show that the method involving the increase in average grain size is limited by the formation of intragranular pores. Furthermore, despite contributing successfully towards decreasing the E b value (which underwent a decline from 3990 V cm −1 to 1133 V cm −1 with an increase in sintering time from 1 h to 2 h), the reduction obtained by this method is found to be much lower compared to that obtained via the nanobelts insertion method (E b = 270 V cm −1). Impedance spectroscopy results showed that the insertion of nanobelts caused a decline in the grain boundary resistance while surface potential measurements proved that this decline in resistance is attributed to the absence of potential barriers along the belts which leads to the formation of a lower resistance percolation path in the varistor.

Influence mechanism of Ni2O3 doping on leakage current of SnO2 varistor ceramics

“…The alterations in grain boundary resistance caused by doping elements can significantly impact the nonlinear characteristics and leakage current of the varistors. 20,21 The values of the intersections far from the imaginary axis in the impedance diagram can be equivalent to the grain boundary resistance (R gb ) of the varistor. The grain boundary resistances for different samples are recorded in Table 1.…”

“…Changes in the total impedance of the varistor are mainly attributed to alterations in the grain boundary resistance. The alterations in grain boundary resistance caused by doping elements can significantly impact the nonlinear characteristics and leakage current of the varistors 20,21 . The values of the intersections far from the imaginary axis in the impedance diagram can be equivalent to the grain boundary resistance ( R gb ) of the varistor.…”

A comparative study between the addition of nano and micro-particles of Co3O4 on the electrical and microstructural properties of a ceramic system based on SnO2

“…A homogeneous dispersion of dopants over the entire volume of the varistor is crucial to obtain the same electrical properties in any direction. In the existing literature, it has been reported that there is a strong relationship between the quality of connections between each of the SnO 2 grains and the value of the coefficient α [20,21]. There are three main types of connections: ohmic, non-ohmic, and conductive.…”

Coalescence growth mechanism of inserted tin dioxide belts in polycrystalline SnO2-based ceramics

“…1a shows the 2D growth of the belt after sintering for 2 h. The SEM image shows that the belt grew both laterally and vertically at the same proportion. Although different belts may present distinct growth rates based on the initial size, the belt has maintained their main role to eliminate shared grain boundaries and, thus, common potential barriers [22]. Consequently, there is no evidence of a more energetic interface, such as a faceted or a twin boundary, capable and responsible for stimulating their growth [13,23,24], raising the idea of a dominating coalescence growth mechanism.…”