Barium Ferrite Disc Magnet: Fired in Carbon Dioxide, Pressed at 12 t/cm² (Went, Philips 1956, Ex. 33)

A barium ferrite made with more iron oxide, 0.4 mol barium carbonate to 3.6 mol, fired an hour at 1300 °C in carbon dioxide. Little oxygen gives the hexagonal crystal BaFe18O27, with some iron in the lower state. It is milled again, bound with nitrocellulose or polyvinyl alcohol, and pressed hard at 12 tonnes per cm². Went's rod held 1,260 gauss with a coercive force of 700 oersted. Source: J. J. Went, G. W. van Oosterhout and E. W. Gorter (Philips), US 2,762,777 (1956), Example 33. They sintered rods; discs and the magnetising are ours. Picture: ferrite magnets, Omegatron, Wikimedia Commons, CC BY-SA 3.0.