R D Shannon, A J Vega
Central Research and Development Dept.,
Experimental Station, Wilmington, DE
19880-0356, USA
B H T Chai
Center for Research in Electro Optics and
Laser, University of Central Florida,
12424 Research Parkway, Suite 400, Orlando, FL 32826, USA
G R Rossman
Division of Geological and Planetary Sciences,
California Institute of Technology, Pasadena, CA 91125, USA
The dielectric constants of a series of
hydrothermally grown berlinite crystals containing increasing
amounts of H2O were determined using a two-terminal
method and empirically determined edge corrections with kT11 ranging from 4.67
to 4.86 and kT33
from 4.54 to 4.76. The extrapolated values for 'dry' berlinite
are kS11 = kS33 = 4.55. Infrared
studies of these crystals show bands at 4400 and 5200 cm-1 which
are attributed respectively to hydroxyl ions and macroscopic and
microscopic inclusions of the 6-7 M HCl/H3PO4 growth
medium. The hydroxyl ions are believed to result from terminal
P-OH groups at the surfaces of inclusions or as (4H)Al
or (3H)Al hydroxyl nests. The OH- groups
have a negligible influence on the dielectric constant, whereas
the inclusions are responsible for the increase in kS11 and kT33 to 4.8 over the
dry value of 4.55.