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Sub‐THz complex dielectric constants of smectite clay thin samples with Na + /Ca ++ ions
Author(s) -
Rahman Rezwanur,
McCarty Douglas K.,
Prasad Manika
Publication year - 2015
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1002/2015jb011956
Subject(s) - dielectric , ion , analytical chemistry (journal) , materials science , clay minerals , mineralogy , chemistry , optoelectronics , organic chemistry , chromatography
Abstract We implement a technique to characterize the electromagnetic properties at frequencies 100 to 165 GHz (3 cm −1 to 4.95 cm −1 ) of oriented smectite samples using an open cavity resonator connected to a submillimeter wave VNA (Vector Network Analyzer). We measured dielectric constants perpendicular to the bedding plane on oriented Na + ion and Ca ++ ion stabilized smectite samples deposited on a glass slide at ambient laboratory conditions (room temperature and room light). The clay layer is much thinner (∼30 μm) than the glass substrate (∼2.18 mm). The real part of dielectric constant, ϵ r e , is essentially constant over this frequency range but is larger in Na + ion than in Ca ++ ion infused clay. The total electrical conductivity (associated with the imaginary part of dielectric constant, ϵ i m ) of both samples increases monotonically at lower frequencies (<110 GHz) but shows rapid increase for Na + ions in the regime > 110 GHz. The dispersion of the samples display a dependence on the ionic strength in the clay interlayers, i.e., ζ potential in the Stern layers.