Effects of sizes of additive particles on suspensions, microstructures, and electrical properties of ZnO varistors

Abstract

The effects of the sizes of the additives on the dispersion of the mixed suspensions, the microstructures, and the comprehensive electrical properties of the ZnO varistors were investigated. The particle size distribution, the viscosity, and the zeta potential of the suspension were characterized to evaluate the effect of the sizes of the additives on the dispersion of the metal oxide particles. The potential gradient, the leakage current, the nonlinear coefficient, the voltage ratio, and the aging coefficient were considered to estimate the effect of the sizes of the additives on the performance of the ZnO varistors. The electrical testing results showed that a proper amount of milling of the additive particles could improve the comprehensive electrical properties, while an excessive milling produced the opposite effect. When the milling time of the additive particles reached 30 minutes, the dispersion of ZnO‐additive mixed suspension was the best. The as‐prepared varistors showed the optimal electrical performance with potential gradient of 310 V/mm, leakage current of 1 μA, nonlinear coefficient of 32.7, voltage ratio of 1.69, and aging coefficient of 0.59.

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

“…The microstructure and technical characteristics of ZnO-based varistors heavily rely on several factors, such as the nature, content, grain size, and grain size distribution of ZnO, which is the principal component [ 101 , 102 ]. Additionally, the selected VFO and dopants [ 7 , 103 , 104 , 105 , 106 , 107 ] also play a crucial role. Furthermore, the techniques used for preparing MOV powder mixtures [ 108 , 109 ], as well as the consolidation (pressing of MOV powders) and densification techniques (sintering of MOV compacts) ( Figure 3 ), including post-annealing and post-processing techniques of MOVs [ 13 , 76 , 77 , 94 , 110 , 111 ], have a significant impact on the properties of MOVs.…”

Investigation The Effect of Particle Size and Annealing on the Performance of Nano/Micro Sized ZnO-Based Varistors

“…The very large shift in the position of the (high) mode of all samples comparison with the theoretical results of indicates that the addition of Bi 2 O 3 and Mn 2 O 3 strengthens the tensile stress of the ZnO crystals. In general, substituting Zn 2+ by Bi 3+ in a ZnO crystal is complicated due to the radius of Bi 3+ is substantially larger than that of Zn 2+ [10,27]. In general, this red-shift in (High) is due to defects and internal strains due to Bi 2 O 3 segregating fundamentally at the grain boundaries as bi-rich phases during the sintering process, and this promotes grain growth and increases the stress [11].…”

“…In general, this red-shift in (High) is due to defects and internal strains due to Bi 2 O 3 segregating fundamentally at the grain boundaries as bi-rich phases during the sintering process, and this promotes grain growth and increases the stress [11]. Also, the lattice distortion is resulting substitution of the dopant ions, such as Mn 2+ and Mn 4+ for Zn 2 during the sintering [10]. The bands of the secondary phases, such as b-Bi 2 O 3 and Mn 3 O 4 , were noted in the Raman spectra.…”

“…On other hand, varistors based on ZnO suffer from some phenomena such as leakage current and consequent Joule heating which leads to degrades the ZnO varistors. To improve the electrical behaviors of the ZnO-varistor system, ZnO varistors often include one or more of metal oxides such as Bi 2 O 3 , Sb 2 O 3 , Co 2 O 3 , MnO 2 , Cr 2 O 3 , Ni 2 O 3 , and SiO 2 , with a few mol% [10,11,12]. Such dopants play an important role on improving the microstructure of ZnO by modifying the grains size and grains growth during the sintering process which can in turn lead to improve the electrical properties.…”

Study of Zinc Oxide Varistors by Incorporating Alkaline-Earth and Rare-Earth Metal Nanofillers

“…Yan et al [20]. The effects of different additive sizes on the dispersion of mixed suspensions, microstructures, and general electrical properties of ZnO varistors were examined.…”