Polycrystalline 18H hexaferrite, method of manufacture, and uses thereof

1. An article comprising a polycrystalline ferrite composition having a formula of

M 5 Mg 2-y Zn y Ti 3 Fe 12 O 31 ,

wherein

M is Ba 2+ , Sr 2+ , or a combination thereof; and

Y=0.25 to 1.8,

having an average grain size of 1 micrometer to 100 micrometers,

wherein the article is an antenna, an inductor, a transformer, or an anti electromagnetic interference material.

2. An article comprising a polycrystalline ferrite composition, having a formula of

Ba 5 Mg 2-y Zn y Ti 3 Fe 12-z O 31 ,

wherein

Y=0.25 to 1.8,

Z=−4 to +4,

having an average grain size of 1 micrometer to 100 micrometers, and

having

a magnetic permeability (μ) of at least 2 at a frequency of 1 to 4 GHz,

a magnetic loss tangent (tan δ μ ) of less than 0.05 at a frequency of 1 to 4 GHz,

a permittivity (ε) of at least 13 to 16 at a frequency of 1 to 4 GHz,

a dielectric loss tangent (tan δ ε ) of less than 0.004 at a frequency of 1 to 4 GHz,

a magnetic loss factor (tan δ μ /μ′) less than 0.02 at a frequency of 1 to 4 GHz,

a cutoff frequency (resonance frequency, f r ) greater than 4 GHz,

a Snoek product greater than 9 GHz, wherein the Snoek product=u′×f r , or

a combination of the foregoing; and

wherein the article is an antenna, an inductor, a transformer, or an anti-electromagnetic interference material.

3. The article of claim 2 , wherein

Y=0.25 to 1.0.

4. The article of claim 1 , wherein Y=0.25 to 1.0.

5. The article of claim 3 , wherein the polycrystalline ferrite composition has

a magnetic permeability (μ) of at least 5 at a frequency of 1 to 4 GHz;

a magnetic loss tangent (tan δ μ ) of less than 0.02 at a frequency of 1 to 4 GHz;

a permittivity (ε) of at least 13 to 15 at a frequency of 1 to 4 GHz;

a dielectric loss tangent (tan δ ε ) of less than 0.003 at a frequency of 1 to 4 GHz;

a cutoff frequency (resonance frequency, f r ) greater than 6 GHz;

a Snoek product greater than 12 GHz, wherein the Snoek product=u′×f r ; or

a combination of the foregoing.

6. The article of claim 1 , wherein the polycrystalline ferrite composition has in-plane easy magnetization and/or an 18H structure.

7. A method of manufacturing a polycrystalline ferrite composition comprising

calcining blended metal source compounds for the polycrystalline ferrite composition as defined in claim 1 ;

reducing particle size of the calcined source compounds to obtain particles having an average particle size of 0.5 micrometer to 10 micrometers;

granulating a mixture of the particles and a binder to obtain granules;

compressing granules into a green body; and

sintering the green body to form the polycrystalline ferrite composition.

8. The method of claim 7 wherein calcining is performed at 900 to 1200° C. for 0.5 hour to 20 hours.

9. The method of claim 8 wherein calcining is performed in an atmosphere of air, nitrogen, oxygen, or a combination thereof.

10. The method of claim 7 wherein sintering is performed at 1000 to 1300° C. for 1 hour to 20 hours.

11. The method of claim 7 wherein sintering is performed in an atmosphere of air, nitrogen, oxygen, or a combination thereof.

12. The method of claim 7 wherein sintering is performed with a temperature heating rate of 1° C./minute to 5° C./min and/or with a cooling rate of 1° C./minute to 5° C./minute.

13. The method of claim 7 wherein reducing particle size comprises crushing and/or grinding the calcined source compounds.

14. The method of claim 7 further comprising sizing the particles.

15. The method of claim 7 further comprising blending the metal source compounds.

16. The method of claim 7 wherein the binder is polyvinylpyrrolidone (PVP), poly(vinyl alcohol) (PVA), polyacrylamide (PAM), poly(acrylic acid) (PAA), polyethylene glycol (PEG), polyethylene oxide (PEO), cellulose acetate, starch, polypropylene carbonate, polyvinyl butyral (PVB), or a combination thereof.

17. The article of claim 1 , wherein the article comprises a composite comprising:

a polymer matrix; and

the polycrystalline ferrite composition as defined in claim 1 , wherein the ferrite composition has a particle size of 0.5 micrometer to 30 micrometers.

18. The article of claim 17 , wherein the composite comprises 5 to 95 volume percent of the polycrystalline hexaferrite, based on the total volume of the composite.

19. The article of claim 17 , wherein the polymer matrix comprises polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyethylene (PE), high density polyethylene (HDPE), low density polyethylene (LDPE), polymethylmethacrylate (PMMA), polyether ether ketone (PEEK), polyethersulfone (PES), or a combination thereof.

20. The article of claim 17 , wherein the composite has

an operating frequency of 1 GHz to 10 GH;

a magnetic permeability (μ) of at least 1.5 at a frequency of 1 to 10 GHz;

a magnetic loss tangent (tan δ μ ) of less than 0.02 at a frequency of 1 to 8 GHz;

a permittivity (ε) of 5 to 6 at a frequency of 1 to 10 GHz;

a dielectric loss tangent (tan δ ε ) of less than 0.004 at a frequency of 1 to 10 GHz;

a magnetic loss factor (tan δ μ /μ′) less than 0.01, or 0.008 at a frequency of 1 to 10 GHz;

a cutoff frequency (resonance frequency, f r ) greater than 8 GHz; or

a combination of the foregoing.

21. A method of making the composite as defined in claim 17 , the method comprising:

combining a polymer, the polycrystalline ferrite composition, optionally a solvent, and optionally an additive composition to form a composite; and

optionally removing the solvent from the composite.

22. The method of claim 21 , wherein the forming comprises shaping the composite.

23. The method of claim 22 , wherein shaping the composite comprises compression molding, injection molding, reaction injection molding, extruding, rolling, casting, or impregnating or laminating onto a reinforcing medium.

24. An article comprising a polycrystalline ferrite composition made by the method of claim 7 .

25. The article of claim 1 , wherein the article is an antenna.