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Barium-Calcium Ferrite Disc Magnet: Equal Barium and Calcium, Sintered at 1280 °C (Went, Philips 1956, Ex. 22)
Charlie

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Charlie

28. October 2026DE
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Barium-Calcium Ferrite Disc Magnet: Equal Barium and Calcium, Sintered at 1280 °C (Went, Philips 1956, Ex. 22)

A ceramic magnet with equal parts barium and calcium: 0.3 mol barium carbonate, 0.3 mol calcium carbonate and 3.1 mol iron oxide, milled 15 hours, pressed and passed through a 1280 °C furnace in 10 minutes, with no presintering. Went's rod held 1,595 gauss with a coercive force of 1,890 oersted. Source: J. J. Went, G. W. van Oosterhout and E. W. Gorter (Philips), US 2,762,777 (1956), Example 22. They sintered rods; discs and the magnetising are ours. Picture: ferrite magnets, Omegatron, Wikimedia Commons, CC BY-SA 3.0.
Advanced
2 days

Instructions

1

Weigh barium carbonate, chalk and iron oxide

Weigh 59.5 g barium carbonate (0.3 mol), 30.2 g calcium carbonate (0.3 mol) and 500.0 g ferric oxide (3.1 mol). Barium carbonate is poisonous if swallowed: gloves and a dust respirator.

Materials for this step:

Barium Carbonate (Witherite)Barium Carbonate (Witherite)59.5 g
Calcium Carbonate - WhitingCalcium Carbonate - Whiting30.2 g
Ferric OxideFerric Oxide500 g

Tools needed:

Balance ScaleBalance Scale
Rubber GlovesRubber Gloves
P100 RespiratorP100 Respirator
2

Mill with alcohol 15 hours, dry, press

Grind with alcohol in a ball mill for 15 hours, dry, and press at 1.5 tonnes per cm² (ours: discs instead of rods). No presintering.

Tools needed:

Iron Ball MillIron Ball Mill
Ethanol - Lab Grade, 95%Ethanol - Lab Grade, 95%
Drying OvenDrying Oven
Hydraulic PressHydraulic Press
Disc Pressing DieDisc Pressing Die
3

Pass through a 1280 °C zone in 10 minutes

Sinter at 1280 °C by passing the pieces through a 10 cm hot zone at 10 mm per minute: 10 minutes in the heat.

Tools needed:

Tube FurnaceTube Furnace
Heat-Resistant GlovesHeat-Resistant Gloves
4

Magnetise the discs

The patent gives no magnetising method. Ours: lay a disc with its faces against the poles of a strong electromagnet, switch the current on, then off. Find which face is north with a compass.

Tools needed:

ElectromagnetElectromagnet
CompassCompass

Materials

3

Tools Required

12

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