Multifaceted improvement of varistors by PVA for desired electrical properties

The effects of polyvinyl alcohol (PVA) on the slurry, granules, green bodies, and sintered varistors were investigated. The results showed that PVA inclusion as a binder not only influenced the mechanical properties of the granules, but also significantly impacted on the dispersibility of the slurry, the microstructure's uniformity, the compactness, and the element doping homogeneity of the varistors. These effects greatly affected the electrical properties, including the non-linear characteristics and the energy withstand capability. The optimal PVA concentration was found to be 0.7 wt%, resulting in varistors with excellent electrical properties: breakdown voltage gradient of 247.7 V/mm, nonlinearity coefficient of 41.0, residual voltage ratio of 1.71 under an 8/20 μs impulse current of 5 kA, and 100% pass rate under 2 ms rectangular waveform impulses of 900 A.