Ferrite Toroid Core: Copper-Zinc Ferrite by the Wet Process, Precipitated with Caustic Soda (Snoek 1948)

Snoek's copper-zinc ferrite made the wet way: copper, zinc and iron salts thrown down together with hot caustic soda, so the particles are very fine and pure. The washed deposit is pre-heated, pressed into a ring and fired in oxygen, with a 30-hour hold at 600 °C. His core reached an initial permeability of 500. Source: J. L. Snoek, US 2,452,529 (Philips, 1948), Example II, wet process. Picture: our diagram.