Microstructures and electrical properties of ZnO–V2O5–MnO2 varistors with low-temperature sintering

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

“…However, ZnO-V 2 O 5 -based systems with V 2 O 5 content over 2 mol.% usually exhibit unsatisfactory varistor properties due to excessive secondary phases formed at the GBs between ZnO grains. On the other hand, V 2 O 5 content of less than 0.1 mol.% does not promote the LPS mechanism at 825−900 °C, hindering the densification of MOVs [ 128 ].…”

“…After mixing the MOV powders with a liquid medium and a small amount (e.g., 0.5–5 wt.%) of organic additive (binders, dispersing agents, among others), drying and sieving them with a typical mesh size of ≤149 μm, the granulation of the MOV composite powders takes place. Binders are selected from polyvinyl alcohol (PVA) [ 15 , 16 , 25 , 38 , 83 , 128 , 160 ], polyvinyl butyral (PVB) [ 27 , 35 , 36 , 124 , 161 , 162 , 163 ], ethyl cellulose (EC) [ 37 ], acrylic latex polymers [ 164 , 165 ], etc. Dispersing agents are chosen from polyurethane polymers [ 108 , 109 ], carboxylic anionic surfactants (sodium or ammonium polyacrylate polymers), phosphate anionic surfactants, cationic surfactants (quaternary ammonium salts), nonionic surfactants [ 166 ], etc.…”