Precipitation and Hardening Behavior of Czochralski Star Sapphire

摘要: Sapphire with 0.11‐wt% titania in solution (mainly as TiO1.5) was aged isothermally air up to 21 days at 1100°–1600°C. Optical studies showed that the solubility limit of exceeded 1400°C air, and consequently needle‐shaped precipitates were developed. For aging temperature between 1100° 1300°C, precipitation initiated grown‐in dislocations subboundaries. This phenomenon attributed rapid oxidation along these defects. Following this initial stage, formed uniformly throughout crystals, they coarsened time. The variation average needle length time measured. Knoop microhardness measurements Ti4+ ions plus attendant defects caused measurable hardening sapphire, but greatest changes resulted from precipitation. Significant 1300°C for 13 days. hardness anisotropy basal plane i.e., KH〈1010〉>KH〈1120〉, not altered by