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Metal Oxide Varistor: Pure Zinc Oxide at 1300 °C, Bismuth Oxide Paste Fired at 800 °C (Masuyama 1972, Ex. 4)

أنشأه

28. أكتوبر 2026

Metal Oxide Varistor: Pure Zinc Oxide at 1300 °C, Bismuth Oxide Paste Fired at 800 °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 1300 °C and fired with the paste at 800 °C, the disc measured a C-value of 100 at 1 mA and a nonlinearity exponent n of 7.5. 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.

متقدم

2 days

التعليمات

Press pure zinc oxide at 340 kg/cm²

Press zinc oxide powder at 340 kg/cm². Example 4 gives no disc size; ours: discs 13 mm across and 2.5 mm thick in the mould of Example 1.

المواد لهذه الخطوة:

مسحوق أكسيد الزنك1 as required

الأدوات المطلوبة:

ميزان ذو كفّتين

مكبس هيدروليكي

قالب كبس الأقراص

قدمة ورنية

Sinter 1 hour at 1300 °C and cool

Heat the pressed disc for 1 hour at 1300 °C, then let it cool to room temperature.

الأدوات المطلوبة:

فرن مفل

Lap both faces

Lap both faces with silicon carbide abrasive. Example 4 gives no thickness.

الأدوات المطلوبة:

حبيبات كربيد السيليكون

قدمة ورنية

Coat with bismuth oxide paste and fire at 800 °C

Coat both lapped faces with a paste of 50 % by weight bismuth oxide in a solution of epoxy resin in butyl alcohol, and fire it in air at 800 °C for 30 minutes. The bismuth oxide diffuses into the zinc oxide. Not given: how much paste, or the strength of the epoxy solution.

المواد لهذه الخطوة:

أكسيد البزموت1 as required

الأدوات المطلوبة:

راتنج إيبوكسي

ن-بيوتانول

فرن مفل

Spray aluminium electrodes and attach leads

Spray a metallised film of aluminium on both faces. Attach a lead wire to each with conductive silver paint, as in Example 1. Ours, after US Army Corps of Engineers EM 1110-2-3401 (1999): wire-arc spray the aluminium from two 3.2 mm wires melted by an 18-40 V DC arc and atomised by compressed air, 15-20 cm from the disc and never at less than 45°, in at least two coats at right angles of 50-75 µm each. Unknown: the paint.

المواد لهذه الخطوة: