Fabrication of Transparent Grain-Oriented Polycrystalline Alumina by Colloidal Processing

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.