Transparent Alumina Ceramics with Sub‐Microstructure by Means of Electrophoretic Deposition
Alumina is a multifunctional ceramic material combining hardness, corrosion and temperature resistance. Furthermore, the optical properties of aluminium oxide ceramic are of great interest. Therefore processing has to beoptimized. Electrophoretic deposition (EPD) is a colloidal process, where ceramic bodies are directly shaped from a stable suspension by an applied electric field. Forming bodies via electrophoretic deposition allows obtaining homogeneous uniform green microstructures with high density. It is a facile and precise technique to synthesize not only monoliths, but also composites with complex geometries [1]. Alumina green bodies were deposited from stabilized aqueous suspensions with and without doping. Green compacts of alumina were evaluated through their pore size distribution and density. Densification behavior was characterized by dilatometric studies, which were conducted at constant heating rate. Doping has a negative influence on suspension preparation, but contributes to the final densification of alumina. Samples were sintered at different temperatures with subsequent post densification via hot isostatic pressing. Transparency was evaluated by spectroscopic measurements. The measured in-line transmission of the samples at 645 nm was more than 50% and this is 58% from the value of sapphire. Mechanical properties of the samples were tested. The influence of dopings on transparency was investigated.