Co2 Z-type ferrite composite material for use in ultra-high frequency antennas

1. A ferrite composition comprising Ba, Co, Fe, and Ir, wherein said ferrite composition comprises a composite of grains of a Z-type hexaferrite phase and grains of a Y-type hexaferrite phase; wherein the Z-type hexaferrite phase has the formula

Ba 3 CO (2+x) Ir x Fe (24-2x) O 41

where x=0.05-0.20.

2. The ferrite composition of claim 1 , wherein x=0.12-0.15.

3. The ferrite composition of claim 1 , wherein the Z-type hexaferrite phase ranges from 65 vol. % to 97.5 vol %, and the Y-type hexaferrite phase ranges from 2.5 vol. % to 35 vol. %.

4. The ferrite composition of claim 1 , wherein the Z-type hexaferrite phase ranges from 65 vol. % to 97.5 vol %, and the Y-type hexaferrite phase comprises a balance.

5. The ferrite composition of claim 1 , further comprising Bi 2 O 3 ranging from 0.2 to 5.0 wt. %.

6. The ferrite composition of claim 5 , wherein the Bi 2 O 3 is present at grain boundaries of the Z-type hexaferrite phase and the Y-type hexaferrite phase.

7. The ferrite composition of claim 1 , wherein the ferrite composition has a real permittivity ranging from about 7 to about 8.

8. The ferrite composition of claim 1 , wherein the ferrite composition has a real permeability ranging from about 7 to about 8.

9. The ferrite composition of claim 1 , wherein a real permittivity of the ferrite composition is equal to a real permeability of the ferrite composition within 10%.

10. The ferrite composition of claim 1 , wherein the ferrite composition has a characteristic impedance matching an impedance of free space within 3%.

11. The ferrite composition of claim 1 , wherein the ferrite composition has a dielectric loss tangent tan δ ∈ ranging from 0.05 to 0.07 over a frequency range of 0.65 to 0.85 GHz.

12. The ferrite composition of claim 1 , wherein the ferrite composition has a magnetic loss tangent tan δ μ ranging from 0.07 to 0.29 over a frequency range of 0.65 to 0.85 GHz.

13. The ferrite composition of claim 1 , wherein the ferrite composition has a dielectric loss factor tan δ ∈ /∈′=0.008±20% at a frequency of 0.8 GHz.

14. The ferrite composition of claim 1 , wherein the ferrite composition has a magnetic loss factor tan δ μ /μ′=0.037±10% at a frequency of 0.8 GHz.

15. A part comprising the ferrite composition of claim 1 , wherein the part is an antenna, microwave antenna, filter, inductor, circulator, or phase shifter.

16. A method of making a ferrite composition comprising:

(a) providing hexaferrite phase precursor compounds comprising Fe, Ba, Co, and Ir,

(b) calcining the hexaferrite phase precursor compounds in air to form a material comprising a composite of grains of a Z-type hexaferrite phase and grains of a Y-type hexaferrite phase;

wherein the Z-type hexaferrite phase has the formula

Ba 3 Co (2+x) Ir x Fe (24-2x) O 41

where x=0.05-0.20.

17. The method of claim 16 , wherein the hexaferrite phase precursor compounds comprise oxides of Fe, Ba, Co, and Ir.

18. The method of claim 16 , wherein the hexaferrite phase precursor compounds comprise 0.2 to 2 wt. % IrO 2 , 20-25 wt. % BaCO 3 , 5-7 wt. % Co 3 O 4 , and 68-74 wt. % Fe 2 O 3 .

19. The method of claim 16 , wherein in step (b), the precursor compounds are calcined at 1000 to 1200° C. for 2 to 10 hours, and further comprising

(c) crushing the material formed in step (b) to form a powder mixture and forming the powder mixture into a compact; and

(d) sintering the powder mixture at 1250 to 1280° C. for 2 to 10 hours in an oxygen atmosphere.

20. The method of claim 16 , further comprising adding Bi 2 O 3 after step (b), the Bi 2 O 3 ranging from 0.2 to 5.0 wt. %.

21. The method of claim 19 , further comprising adding a binder to the powder mixture, wherein the binder is selected from the group consisting of a polyvinyl alcohol, methyl cellulose, polyethylene glycol, and poly(alkylene carbonate).

22. The method of claim 21 , wherein the powder mixture comprises 8% to 12% by weight of the polyvinyl alcohol.