Preparation of finely divided ferrite powders

A process for the preparation of an isotropic ferrite powder having a spinel structure, of the formula MeFe.sub.2 O.sub.4 (I), where Me=a Mn+b Ni+c Zn+d Co+e Fe(II), and the atomic weight ratios a, b, c, d and e are each from 0 to 1 and their sum is 1, wherein one or more Me salts, iron(III) chloride and sodium carbonate and/or potassium carbonate are mixed as powders to form a mixture of powders, the mixture obtained is heated at from 800.degree.-1200.degree. C. and the resulting isotropic ferrite is isolated from the heated mixture by leaching with water.

A process for the preparation of a hexagonal Me.sub.2.sup.1 Y ferrite of the formula M.sub.2.sup.1 Me.sub.2.sup.1 Fe.sub.12 O.sub.22 (II), where M.sup.1 is barium, strontium, calcium and/or lead and Me.sup.1 is divalent manganese, copper, iron, cobalt, nickel, zinc, magnesium and/or equimolar amounts of lithium and trivalent iron, wherein an M.sup.1 chloride or carbonate, an Me.sup.1 chloride or carbonate, iron(III) chloride and sodium carbonate and/or potassium carbonate are mixed as powders to form a mixture of powders, the mixture obtained is heated at from 800.degree. to 1050.degree. C. and the flaky hexagonal Me.sub.2.sup.1 Y ferrite formed is then isolated from the resulting melt of sodium chloride and/or potassium chloride by leaching with water.

A process for the preparation of a finely divided hexagonal ferrite of the formula M.sup.2 (Me.sup.2 Ti).sub.x Fe.sub.12-2x O.sub.19 (III), where M.sup.2 is barium or strontium, Me.sup.2 is zinc, nickel and/or cobalt and x is from 0 to 2.0, wherein a barium or strontium salt, iron(III) chloride and sodium carbonate and/or potassium carbonate are mixed as powders, with or without a salt of zinc, nickel and/or cobalt as powders and a powdered titanium compound to form a mixture of powders, the mixture obtained is heated at from 700.degree. to 1100.degree. C. and the resulting finely divided flaky hexagonal ferrite of the above composition is then isolated from the heated mixture by leaching with water.