Metal Oxide Varistor: Pure Zinc Oxide at 1350 °C, Bismuth Oxide Paste Fired at 600 °C (Masuyama 1972, Ex. 4)

A varistor made the other way round: a disc of pure zinc oxide, sintered, with bismuth oxide fired into its faces from a paste instead of mixed in. Sintered at 1350 °C and fired with the paste at 600 °C, the disc measured a C-value of 13 at 1 mA and a nonlinearity exponent n of 4.2. Masuyama found that firing on the bismuth oxide paste raises n a great deal over mixing it in. Source: T. Masuyama, M. Matsuoka and T. Nishi (Matsushita), US 3,663,458 (1972), Example 4. Unknown: what the silver paint is, and how strong the epoxy solution of the paste is. The spraying is ours, after US Army Corps of Engineers EM 1110-2-3401 (1999). The 10 g batch is our arithmetic. Picture: the patent's drawing.