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Metal Oxide Varistor: Zinc Oxide, 0.5 % Bismuth Oxide, 0.03 % Manganese Dioxide, 1350 °C (Masuyama 1972, Ex. 2)
Masuyama, Matsuoka and Nishi found that adding a second oxide to zinc oxide and bismuth oxide changes the varistor a great deal. This is their Example 2 with manganese dioxide: 99.47 % zinc oxide, 0.5 % bismuth oxide and 0.03 % manganese dioxide by moles, sintered at 1350 °C. The disc measured a C-value of 16 at 1 mA and a nonlinearity exponent n of 2.6.
Source: T. Masuyama, M. Matsuoka and T. Nishi (Matsushita), US 3,663,458 (1972), Example 2. Unknown: how the aluminium is sprayed on and what the silver paint is. The 10 g batch is our arithmetic. Picture: the patent's drawing.
Advanced
1 day
Instructions
1
1
Weigh 99.47 : 0.5 : 0.03 and wet-mill 5 hours
Weigh 99.47 : 0.5 : 0.03 and wet-mill 5 hours
Mix zinc oxide, bismuth oxide and manganese dioxide 99.47 : 0.5 : 0.03 by moles. Ours, for 10 g: 9.717 g zinc oxide, 0.28 g bismuth oxide, 0.003 g manganese dioxide (our arithmetic). Mill wet for 5 hours, then dry. Unknown: the milling liquid.
Materials for this step:
Zinc Oxide Powder9.717 g
Bismuth Oxide0.28 g
Manganese Dioxide (Pyrolusite)0.003 gTools needed:
Balance Scale
Iron Ball Mill
Drying Oven2
2
Press discs 13 mm by 2.5 mm
Press discs 13 mm by 2.5 mm
Press the powder in a mould into discs 13 mm across and 2.5 mm thick at 340 kg/cm², as in Example 1.
Tools needed:
Hydraulic Press
Disc Pressing Die
Vernier Caliper3
3
Sinter 1 hour at 1350 °C and furnace-cool
Sinter 1 hour at 1350 °C and furnace-cool
Sinter the discs in air for 1 hour at 1350 °C, then let them cool in the furnace to room temperature (about 15-30 °C).
Tools needed:
Muffle Furnace4
4
Lap to 10 mm by 1.5 mm
Lap to 10 mm by 1.5 mm
Lap both faces with 600-mesh silicon carbide. The finished disc is 10 mm across and 1.5 mm thick.
Tools needed:
Silicon Carbide GritVernier Caliper5
5
Spray aluminium electrodes and attach leads
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. Unknown: the spraying method and the paint.
Materials for this step:
Aluminium Ingot1 as required
Silver Conductive Paint1 as required
Copper Wire2 piecesTools needed:
Unknown Metal Spraying MethodVernier CaliperMaterials
6- 9.717 gPlaceholder
- 0.28 gPlaceholder
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- 1 as requiredPlaceholder
- 1 as requiredPlaceholder
- 2 piecesPlaceholder
Tools Required
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