A method for the joining of ceramic pieces with a hermetically sealed joint comprising brazing a layer of joining material between the two pieces. The wetting and flow of the joining material is controlled by the selection of the joining material, the joining temperature, the joining atmosphere, and other factors. The ceramic pieces may be on a non-diffusable type, such as aluminum nitride, alumina, beryllium oxide, and zirconia, and the pieces may be brazed with an aluminum alloy under controlled atmosphere. The joint material is adapted to later withstand both the environments within a process chamber during substrate processing, and the oxygenated atmosphere which may be seen within the shaft of a heater or electrostatic chuck.

Systems, structures, devices, and fabrication processes for ceramic matrix composites suitable for use in a nuclear reactor environment and other applications requiring materials that can withstand high temperatures and/or highly corrosive environments are disclosed. In one aspect, a ceramic composite structure is provided. The structure comprises a chamber including an external shell and a hollow space inside the external shell. The external shell includes an inner composite layer including a first composite structure, a middle composite layer placed outside of the inner composite layer, the middle composite layer including a second composite structure that is different from the first composite structure, and an outer monolithic layer that has a spatially uniform material property and placed outside of the middle composite layer.

The disclosed technology generally relates dielectric materials, and more particularly to a combination of co-fireable dielectric materials that can be attached to each other without the use of adhesives. In an aspect, a composite article comprises a magnetic portion comprising a nickel zinc ferrite. The composite article additionally comprises a non-magnetic portion contacting the magnetic portion, the non-magnetic portion comprising a spinel-structured oxide comprising Mg.sub.2-xAl.sub.2xTi.sub.1-xO.sub.4 and having a dielectric constant between about 7 and 14, wherein 0<x1.

Disclosed herein are embodiments of low temperature co-fireable dielectric materials which can be used in conjunction with high dielectric materials to form composite structures, in particular for isolators and circulators for radiofrequency components. Embodiments of the low temperature co-fireable dielectric materials can be scheelite or garnet structures, for example, bismuth vanadate. Adhesives and/or glue is not necessary for the formation of the isolators and circulators.

Disclosed herein is a dual density disc comprising a dense outer tube comprising alumina having a purity of greater than 99%; and a porous core comprising alumina of a lower density than a density of the dense outer tube; wherein the porous core has an alumina purity of greater than 99%. Disclosed herein too is method comprising disposing in a dense outer tube a slurry comprising alumina powder and a pore former; heating the dense outer tube with the slurry disposed therein to a temperature of 300 to 600? C. to activate the pore former; creating a porous core in the dense outer tube; and sintering the dense outer tube with the porous core at a temperature of 800 to 2000? C. in one or more stages.

A method of forming a composite material for use as an isolator or circulator in a radiofrequency device comprises providing a low temperature fireable outer material, the low fireable outer material having a garnet or scheelite structure, inserting a high dielectric constant inner material having a dielectric constant above 30 within an aperture in the low temperature fireable outer material, and co-firing the lower temperature fireable outer material and the high dielectric constant inner material together at temperature between 650-900? C. to shrink the low temperature fireable outer material around an outer surface of the high dielectric constant inner material to form an integrated magnetic/dielectric assembly without the use of adhesive or glue.

A method of making a stoichiometric monazite (LaPO.sub.4) composition or a mixture of LaPO.sub.4 and LaP.sub.3O.sub.9 composition, as defined herein. Also disclosed is a method of joining or sealing materials with the compositions, as defined herein.

A method is provided and suggests grading of a CMC (Ceramic Matrix Composite) structure as a function of dielectric constant by altering the solid loading (SL) ratio of the individual composite layers. The slurry is applied either by impregnation into the ceramic fabrics or by coating on ceramic fibers. The final structure is prepared by piling up prepregs or weaving ceramic fibers with specific SL ratio, drying and firing.

The disclosed technology generally relates dielectric materials, and more particularly to a combination of co-fireable dielectric materials that can be attached to each other without the use of adhesives. In an aspect, a composite article comprises a magnetic portion comprising a nickel zinc ferrite. The composite article additionally comprises a non-magnetic portion contacting the magnetic portion, the non-magnetic portion comprising a spinel-structured oxide comprising Mg.sub.2-xAl.sub.2xTi.sub.1-xO.sub.4 and having a dielectric constant between about 7 and 14, wherein 0<x1.

A cylindrical sputtering target according to the present invention comprises: a metallic cylindrical substrate; and a ceramic cylindrical target material joined to an outer peripheral side of the cylindrical substrate and integrally formed so as to have a length of 750 mm or more in an axial direction, wherein a variation coefficient of a bulk resistivity in an axial direction is 0.05 or less on the outer peripheral surface of the cylindrical target material.