Frequently, ceramics are applied for the filtration of aggressive liquids. To separate substance mixtures containing variably sized particles, various filters have to be arranged in series. By means of stepwise filtration, coarse particles are removed first, smaller particles later on. The ceramic elements used for this purpose are structures of variable pore size. This may cause stability problems, as their joints are rather weak. At the KIT Institute for Applied Materials - Ceramics in Mechanical Engineering (IAM), scientists have now succeeded in producing a filter that consists of two ceramic phases of variable pore size. These filters are monolithic, which means that they are connected to each other without any adhesive. For the first time, freeze casting is combined with slip casting for filter manufacture. In freeze casting, an aqueous ceramic suspension, e.g. of aluminum oxide, is frozen with a controlled temperature gradient. The resulting ice lamellae enclose the ceramic particles. Upon ice sublimation, i.e. transition from the solid to the gaseous phase, a green body with a lamellar pore structure forms. When ceramic slip is applied to this green body, it partly penetrates into the ceramic structure. Subsequent sintering yields a single ceramic component having a structure of coarser lamellae (width and spacing 20 - 250 µm) on one side and a finer, statistically distributed pore structure on the other (pore sizes ranging from 0.2 - 5 µm). Both phases are connected by a transition zone. Consequently, mechanical stability exceeds that of joined ceramics. The pore size and the pore structure can be adjusted flexibly by the process conditions. Such ceramics are predestined for use as filters for stepwise separation, but may also be applied as insulating material. KIT looks for industry partners interested in an application and further development of the technology.