Magnetic-dielectric assemblies and methods of fabrication

1. A method for fabricating a magnetic-dielectric assembly comprising acts of:

applying an adhesive including a ceramic material in an epoxy matrix to at least a portion of at least one of an interior surface of a dielectric ceramic annular cylinder and at least a portion of a surface of a magnetic ceramic rod; and

assembling the magnetic ceramic rod coaxially inside the dielectric ceramic annular cylinder to form the magnetic-dielectric assembly.

2. The method of claim 1 wherein the epoxy matrix has a dielectric constant lower than a dielectric constant of the ceramic material.

3. The method of claim 1 wherein epoxy matrix has a thermal conductivity lower than a thermal conductivity of the ceramic material.

4. The method of claim 1 wherein the ceramic material includes powdered alumina.

5. The method of claim 4 wherein the powdered alumina includes substantially spherical particles with a median diameter in a range of from about 0.1 micrometers to about 10 micrometers.

6. The method of claim 4 further comprising an act of selecting an adhesive including from about 0.4 to about 1.2 grams of powdered alumina per gram of adhesive.

7. The method of claim 4 wherein the powdered alumina has a purity of greater than about 99%.

8. The method of claim 1 further comprising an act of cutting the magnetic-dielectric assembly to form at least one magnetic-dielectric disc assembly.

9. The method of claim 8 wherein the act of cutting the magnetic-dielectric assembly includes sawing the magnetic-dielectric assembly.

10. The method of claim 8 wherein the act of cutting the magnetic-dielectric assembly includes removing adhesive from a blade of a saw with the ceramic material.

11. The method of claim 8 wherein the act of cutting the magnetic-dielectric assembly includes forming at least one magnetic-dielectric disc assembly having a desired dimensional parameter.

12. The method of claim 11 wherein the desired dimensional parameter is at least one of thickness, variation in thickness, surface roughness, and circularity.

13. The method of claim 11 wherein the at least one magnetic-dielectric disc assembly varies in thickness by less than 0.025 mm after cutting and before any further processing.

14. The method of claim 8 further comprising an act of selecting the epoxy matrix and the ceramic material to provide the adhesive with a dielectric constant such that an insertion loss at a frequency of 900 MHz of a microwave isolator including the at least one magnetic-dielectric disc assembly is decreased by about 0.2 decibels relative to an assembly of substantially the same materials except having an adhesive free of the ceramic material.

15. The method of claim 8 further comprising an act of selecting the epoxy matrix and the ceramic material to provide the adhesive with sufficient thermal conductivity such that during cutting of the magnetic-dielectric assembly the adhesive does not melt.

16. The method of claim 1 wherein the ceramic material has a thermal conductivity of at least 0.08 cal/(sec·cm·K).

17. The method of claim 1 wherein the magnetic ceramic rod includes yttrium-iron-garnet and the dielectric ceramic annular cylinder includes MgO—CaO—ZnO—Al 2 O 3 —TiO 2 .

18. A method for fabricating a magnetic-dielectric assembly comprising acts of:

applying an adhesive to at least a portion of at least one of an interior surface of a dielectric ceramic annular cylinder and at least a portion of a surface of a magnetic ceramic rod, the adhesive including a ceramic material;

assembling the magnetic ceramic rod coaxially inside the dielectric ceramic annular cylinder to form the magnetic-dielectric assembly; and

cutting the magnetic-dielectric assembly to form at least one magnetic-dielectric disc assembly.

19. The method of claim 18 wherein the adhesive further includes an epoxy matrix.

20. The method of claim 19 wherein the epoxy matrix has a dielectric constant lower than a dielectric constant of the ceramic material.

21. The method of claim 19 wherein the epoxy matrix has a thermal conductivity lower than a thermal conductivity of the ceramic material.

22. The method of claim 18 wherein the act of cutting the magnetic-dielectric assembly includes sawing the magnetic-dielectric assembly.

23. The method of claim 18 wherein the act of cutting the magnetic-dielectric assembly includes removing adhesive from a blade of a saw with the ceramic material.

24. The method of claim 18 wherein the at least one magnetic-dielectric disc assembly varies in thickness by less than 0.025 mm after cutting and before any further processing.

25. The method of claim 18 further comprising an act of selecting an adhesive matrix and the ceramic material to provide the adhesive with a dielectric constant such that an insertion loss at a frequency of 900 MHz of a microwave isolator including the at least one magnetic-dielectric disc assembly is decreased by about 0.2 decibels relative to an assembly of substantially the same materials except having an adhesive free of the ceramic material.

26. The method of claim 18 wherein the magnetic ceramic rod includes yttrium-iron-garnet.

27. The method of claim 18 wherein the dielectric ceramic annular cylinder includes MgO—CaO—ZnO—Al 2 O 3 —TiO 2 .