Effect of H2O on dielectric properties of berlinite: I. Dielectric constant

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.