High Resolution Synchrotron X-Radiation Diffraction Imaging of Crystals Grown in Microgravity and Closely Related Terrestrial Crystals.
Irregularities in three crystals grown in space and in four terrestrial crystals grown under otherwise comparable conditions have been observed in high resolution diffraction imaging. The images provide important new clues to the nature and origins of irregularities in each crystal. For two of the materials, mercuric iodide and lead tin telluride, more than one phase (an array of non diffracting inclusions) was observed in terrestrial samples; but the formation of these multiple phases appears to have been suppressed in directly comparable crystals grown in microgravity. The terrestrial seed crystal of triglycine sulfate displayed an unexpected layered structure, which propagated during directly comparable space growth. Terrestrial Bridgman regrowth of gallium arsenide revealed a mesoscopic structure substantially different from that of the original Czochralski material. A directly comparable crystal is to be grown shortly in space.
National Institute of Standards and Technology, Gaithersburg, MD 20899.
Bruce
B
Steiner
National Institute of Standards and Technology, Gaithersburg, MD 20899.
Ronald C
RC
Dobbyn
National Institute of Standards and Technology, Gaithersburg, MD 20899.
David
D
Black
National Institute of Standards and Technology, Gaithersburg, MD 20899.
Harold
H
Burdette
National Institute of Standards and Technology, Gaithersburg, MD 20899.
Masao
M
Kuriyama
National Institute of Standards and Technology, Gaithersburg, MD 20899.
Richard
R
Spal
EG&G Energy Measurements, Goleta, CA 93116.
Lodewijk
L
van den Berg
NASA Langley Research Center Hampton, VA 23665.
Archibald
A
Fripp
NASA Langley Research Center Hampton, VA 23665.
Richard
R
Simchick
Alabama A&M University, Huntsville, AL 35762.
Ravindra B
RB
Lal
Alabama A&M University, Huntsville, AL 35762.
Ashok
A
Batra
GTE Laboratories, Waltham, MA 02254.
David
D
Matthiesen
GTE Laboratories, Waltham, MA 02254.
Brian
B
Ditchek
crystal growth; diffraction; gallium arsenide; high resolution; lead tin telluride; mercuric iodide; microgravity; synchrotron; topography; triglycine sulfate