Sub‐THz complex dielectric constants of smectite clay thin samples with Na+/Ca++ ions. Issue 9 (29th September 2015)

• Record Type: Journal Article
• Authors: Rahman, Rezwanur; McCarty, Douglas K.; Prasad, Manika
• Is Part Of: Journal of geophysical research. Volume 120:Issue 9(2015:Sep.)
• Page Start: 6219
• Page End: 6225
• Publication Date: 2015-09-29
• Subjects: clay -- complex dielectric permittivity -- millimeter wave -- terahertz; Geomagnetism -- Periodicals; Geochemistry -- Periodicals; Geophysics -- Periodicals; Earth sciences -- Periodicals; 551.1
• DOI: 10.1002/2015JB011956
• Languages: English
• ISSNs: 2169-9313

Abstract

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. Key Points: The pore scale electrical environment of clays The connections between EM parameters and components of surface chemistry We measure the dispersion of the dielectic permittivity up to 160 GHz