Grain‐oriented polycrystalline alumina (PCA) ceramics with very high, nearly single‐crystal transparency were successfully fabricated through colloidal processing in a high magnetic field followed by hot isostatic pressing. The c‐axis of the produced material was oriented along the direction parallel to the magnetic field. The transmittance of the specimen with a thickness of 0.8 mm was 78% at a wavelength of 650 nm, close to the reported value of 84.5% for sapphire and more than 10% higher than the largest transmittance magnitude ever reported for PCA ceramics. In addition, the Na salt of 4,5‐dihydroxy‐1,3‐benzenedisulfonic acid (named “Tiron”) was found to be a highly effective dispersant for processing high‐purity materials.

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A new, convenient, and inexpensive approach to process and granulate titania powders by a chemical route is proposed. It is based on the use of a formulation that includes a polyanion such as poly(sodium 4-styrenesulfonate) (PSS). Such a polyelectrolyte is most often considered to achieve dispersion of oxide powders in water. Basically, it adsorbs onto the surface of particles and induces electrical and/or steric interactions between particles in the suspension, which prevents agglomeration and rapid sedimentation. The advantages of polyelectrolytes in ceramic processing is well documented in the literature to produce low viscosity suspensions that are further used to form ceramic parts. In the case of TiO2 powders, such aqueous dispersions were obtained by adding small quantities of PSS. However, when exploring the behavior of mixtures containing lower contents of dispersant, we have discovered that, well below the optimum concentration required to get stable dispersions, the polyelectrolyte can act as a binder for titania particles. This can confer cohesion to the agglomerates, which can be processed to form large size (e.g., millimeter size) spheres. This phenomenon takes place when the oxide surface carries both positive and negative electrical charges and can be explained on a simple basis involving surface chemistry. For the optimum concentration of PSS that disperses titania, a polycation such as chitosan should be added to get spheres. This simple technique is expected to receive increasing attention due its potentialities and strong advantages with respect to other granulation techniques, such as spray-drying, which are energy consuming.