Production of single crystalline ferrite particles

Claim 1

A method for producing single crystal strontium ferrite or barium ferrite particles in the form of hexagonal plates about 0.5μ to 2.0μ in diameter and less than about one-fourth of said diameter in thickness, which comprises: (a) reacting an admixture of (i) about 4.3 to 6.5 moles, expressed as ferric oxide, of an iron compound selected from the group consisting of ferric hydroxide, ferric oxyhydroxide, calcined porous ferric oxide and ferric oxide having a particle size less than about 0.8μ; (ii) about one mole, expressed as metal oxide, of at least one metal compound selected from the group consisting of the oxides, hydroxides, carbonates and carboxylates of strontium and barium; and (iii) about 0.05- 2 moles of a metal chloride flux selected from the group consisting of strontium chloride, barium chloride and mixtures thereof, at a temperature between the melting point of said metal chloride flux and 1300° C. to form said strontium ferrite or barium ferrite particles having the stoichiometric composition MO·6 Fe 2 O 3 wherein M is divalent strontium or barium; (b) cooling the resultant reaction mixture to form a cake comprising said single crystal ferrite particles and water soluble flux intervened therebetween; and (c) extracting said water-soluble flux from said particles.

Claim 2

A method for producing single crystal strontium ferrite or barium ferrite particles in the form of hexagonal plates about 0.5μ to 2.0μ in diameter and less than about one-fourth of said diameter in thickness, which comprises: (a) reacting an admixture of (i) about 4.3 to 6.5 moles, expressed as ferric oxide, of an iron compound selected from the group consisting of ferric hydroxide, ferric oxyhydroxide, calcined porous ferric oxide and ferric oxide having a particle size less than about 0.8μ; (ii) about one mole, expressed as metal oxide, of at least one metal compound selected from the group consisting of the oxides, hydroxides, carbonates and carboxylates of strontium and barium; and (iii) about 0.05- 2 moles of a metal chloride flux selected from the group consisting of strontium chloride, barium chloride and mixtures thereof, at a temperature between the melting point of said metal chloride flux and 1300° C. to form said strontium ferrite or barium ferrite particles having the stoichiometric composition MO·6 Fe 2 O 3 wherein M is divalent strontium or barium; (b) cooling the resultant reaction mixture to form a cake comprising said single crystal ferrite particles and water soluble flux intervened therebetween; and (c) extracting said water-soluble flux from said particles.