Frederik Kotz‐Helmer

Transparent polycrystalline magnesium aluminate (MAS) spinel ceramics are of great interest for industry and academia due to their excellent optical and mechanical properties. However, shaping of MAS is notoriously challenging especially on the microscale requiring hazardous etching methods. Therefore, a photochemically curable nanocomposite is demonstrated that can be structured using high‐resolution two‐photon lithography. The printed nanocomposites are converted intro transparent MAS by subsequent debinding, sintering, and hot isostatic pressing. The resulting transparent spinel ceramics exhibit a surface roughness S q of only 10 nm and can be shaped with minimum feature sizes of down to 13 µm. This technology will be important for the production of microstructured ceramics used for optics, photonics, or photocatalysis.