The complete sets of elastic constants of 4H and 6H silicon carbide si
ngle crystals were determined by Brillouin scattering. The elastic con
stants of 6H SiC are C-11=501+/-4, C-33-553+/-4, C-44=163+/-4, C-12=11
1+/-5, and C-13=52+/-9 GPa; the corresponding ones of 4H SiC are the s
ame within experimental uncertainties. The compressibility, 4.5x10(-3)
GPa, is about 3-5 times smaller than those reported for polycrystalli
ne SiC materials. (C) 1997 American Institute of Physics.