Single Crystal Growth of Beta-Al2O3 for Iso-Index Filters

摘要

Single crystals of Beta-Al203 with a nominal composition of Na2O.11 Al203 weregrown from stoichiometric melts contained in an iridium crucible. Seeding was achieved from an Al203 single crystal. The growth axis was along a and X-ray data confirmed the unit cell parameters of a = 5.595 A and c = 22.531 A. The top and bottom lattice constants of the boules were equal to + 0.002 A and indicated a fairly uniform composition. The measured density was 3.25 g/cm3. The boules remained physically intact with no major cracks. However some cleavage progressed on the basal planes as determined by the appearance of interference fringes. Water vapor and C02 did not enhance the cracking. Crystals were stored in a desiccator but continued to cleave. Ionic diffusions of Nal+, Agl+, Pb2+, Rbl+, Ca2+, Cd2+, TI l+ were performed by immersion Of Beta-Al203 into nitrate or chloride melts at temperatures of 360-7400C. The amount of exchange was Crystal Growth, Beta-Al2O3, Iso-Index filters.