Ceramic processing for multi-material devices with complex geometry

Recent antenna designs have a complex 3D distribution of different materials that must form a cohesive, and often highly asymmetric entity. The distinct materials in such designs have special dielectric and magnetic properties, and often low electromagnetic losses. This implies that the materials of choice are mainly oxides that are made by ceramic routes for practical reasons. Ceramic routes start from powders that are consolidated into a pre-designed, "green," shape, followed by thermal processing to realize the target micro-structure. Thermal processing can be described as a sequence of drying to remove volatile processing liquids, removal of binders and other additives, and finally sintering. Commensurate ceramic processing of complex multi-phase components provide major challenges due to unavoidable variations in intrinsic and process properties of different materials. Methods to overcome these problems are only beginning to become available. Examples of promising routes include use of high-density colloidal deposition methods, advanced feed-back control during drying and additive removal, pre-designed thermal shrinkage behavior, and rapid processing techniques developed by the semi-conductor industry.