Accession Number : AD0447345

Title :   DISLOCATION STRUCTURES IN SINGLE-CRYSTAL AI2O3,

Corporate Author : AIR FORCE CAMBRIDGE RESEARCH LABS HANSCOM AFB MA

Personal Author(s) : Stephens, D. L. ; Alford, W. J.

Report Date : 16 SEP 1963

Pagination or Media Count : 1

Abstract : Chemical polishing and etching techniques were usedto reveal the dislocation structures of sapphire and ruby crystals grown by the flamefusion and flux techniques. The average density of edge dislocations lying in prism planes was 3.0 X 10 to the 5th power/sqcm which could be changed only slightly by chromium additions and annealing at 2000 C. An average basal dislocation density of 2 X 10 to the 6th power/sqcm decreased 35 to 80% on annealing. Crystal orientation (i.e., angle between the c axis and the growth axis) showed no effect on dislocation density but a pronounced effect on subboundary arrangement and density. The substructure of 0 degree crystals was more complex than that of 90 degree crystals; 60 degree crystals possessed a structure intermediate between 0 degree and 90 degree. Principal observations included (1) prismatic and basal slip on all as-grown crystals; (2) profuse basal slip, readily polygonized on annealing; (3) dislocation densities of flux crystals lower than those of Verneuil crystals; and (4) a rare form of basal twinning, on all flux crystals. (Author)

Descriptors :   (*SINGLE CRYSTALS, CRYSTAL DEFECTS), (*ALUMINUM COMPOUNDS, OXIDES), RUBY, SAPPHIRE, ETCHED CRYSTALS, CRYSTAL SUBSTRUCTURE, CRYSTAL GROWTH, HEAT TREATMENT, CHROMIUM, IMPURITIES.

Distribution Statement : APPROVED FOR PUBLIC RELEASE