High-resolution structuring of transparent spinel ceramics

Transparent ceramics such as magnesium aluminate spinel (MAS) are an outstanding class of materials that combine high optical transparency with remarkable mechanical, chemical and thermal strength. They are particularly interesting for micro-optical applications, since MAS offers a high refractive index in combination with a low optical dispersion, which is inaccessible for other materials including glasses and polymers. However transparent polycrystalline MAS is notoriously difficult to microstructure. Methods such as hot pressing or slip casting only allow simple geometries like plates or domes to be manufactured. More complex geometries require time-consuming and cost-intensive post-processing. We have therefore developed a thermoplastic nanocomposite that can be structured with high accuracy by injection molding. The nanocomposite can subsequently be transformed into a transparent polycrystalline MAS ceramic with a transparency close to the theoretical maximum by thermal debinding, sintering and hot isostatic pressing (HIP). This innovative process makes transparent ceramics for optics and photonics available at low cost and with high production rates.