Abstract Oriented lead ferrites which yield superior ceramic permanent magnets are produced by the four-step process of A. PREPARING SMALL PARTICLES OF AGGLOMERATED LESS THAN 0.1 MICRON GRAINS OF FERRIC OXIDE AND LEAD OXIDE, B. MAINTAINING THE PARTICLES OF AGGLOMERATED OXIDES AT TEMPERATURES OF FROM ABOUT 700*C to 1,000*C for up to about 24 hours to cause the oxides to react (ferritize) and form less than 0.5 micron diameter crystallites of lead ferrite, C. SINTERING THE CRYSTALLITES INTO A SOLID BODY EITHER BY MAINTAINING THEM AT FROM 750*C to 1,000*C for not more than 2 hours, or preferably by maintaining them at from 700*C to 1,000*C while applying pressure, and D. HOT FORGING THE BODY BY APPLYING PRESSURES OF UP TO ABOUT 30,000 PSI AT TEMPERATURES OF FROM 700*C to 1,050*C.
The process in accordance with claim 1 wherein in step (b) the temperature employed is in the range of from 750*C to 900*C and the heating period is a time of from 0.5 to 8 hours.
Claim 2
Dependent Claim
45 words
The process in accordance with claim 2 wherein in step (d) the temperature employed is in the range of 750*C to 1,000*C, the pressure is from about 3,000 psi to 20,000 psi and the time period for forging is from 0.1 minutes to 5 minutes.
Claim 3
Dependent Claim
32 words
The process in accordance with claim 1 wherein the sintering in step (c) is carried out in not more than 15 minutes while applying a pressure of from 1,000 to 30,000 psi.
Claim 4
Dependent Claim
45 words
The process in accordance with claim 4 wherein in step (d) the temperature employed is in the range of 800*C to 950*C, the pressure is from about 3,000 psi to 10,000 psi and the time period for forging is from 0.1 minute to 5 minutes.
Claim 5
Dependent Claim
40 words
The process in accordance with claim 5 wherein in step (c) the sintering is carried out in from 1 to 10 minutes at a temperature of from 800*C to 950*C and a pressure of from 3,000 psi to 10,000 psi.
Claim 6
Dependent Claim
123 words
In a process for preparing a solid ferrite body having oriented crystallites suitable for forming anisotropic ceramic magnets wherein substantial crystallite orientation is induced in the ferrite body by deforming the body with from 1,000 to 30,000 psi pressure at a temperature in the range of from about 700*C to about 1,050*C, the improvement which comprises hot forging a solid ductile ferrite body consisting essentially of ferric oxide and lead oxide in the molar ratio of from 5 to 6.5 moles of ferric oxide for each mole of lead oxide and composed of uniform ferrite grains, said grains having an average diameter of less than 0.7 micron with not more than 10 percent of said grains having diameters greater than about 1.0 micron.
Claim 7
Dependent Claim
25 words
The process in accordance with claim 7 wherein the average grain size of the body to be deformeD is from 0.3 micron to 0.7 micron.